WorldWideScience

Sample records for alkoxides

  1. metal alkoxides

    Indian Academy of Sciences (India)

    substituent effects in the head-to-tail double insertion reactions observed ... an internal standard. The yield of diphenyl carbodii- mide was further verified by isolating it as diphenyl urea after hydrolysis. The organic fraction obtained in the catalytic metathesis .... insertion of PhNCO into metal alkoxide 1a to generate. Table 1.

  2. Alkoxide routes to Inorganic Materials

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, George Harrison [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2007-12-01

    An all alkoxide solution chemistry utilizing metal 2-methoxyethoxide complexes in 2-methoxyethanol was used to deposit thin-films of metal oxides on single-crystal metal oxide substrates and on biaxially textured metal substrates. This same chemistry was used to synthesize complex metal oxide nanoparticles. Nuclear Magnetic Resonance spectroscopy was used to study precursor solutions of the alkaline niobates and tantalates. Film crystallization temperatures were determined from x-ray diffraction patterns of powders derived from the metal oxide precursor solutions. Film structure was determined via x-ray diffraction. Film morphology was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Epitaxial thin-films of strontium bismuth tantalate (SrBi{sub 2}Ta{sub 2}O{sub 9}, SBT) and strontium bismuth niobate (SrBi{sub 2}Nb{sub 2}O{sub 9}, SBN) were deposited on single crystal [1 0 0] magnesium oxide (MgO) buffered with lanthanum manganate (LaMnO{sub 3}, LMO). Epitaxial thin films of LMO were deposited on single crystal [100] MgO via Rf-magnetron sputtering and on single crysal [100] lanthanum aluminate (LaAlO{sub 3}) via the chemical solution deposition technique. Epitaxial thin-films of sodium potassium tantalate (na{sub 0.5}K{sub 0.5}TaO{sub 3}, NKT), sodium potassium niobate (Na{sub 0.5}K{sub 0.5}NbO{sub 3}, NKN) and sodium potassium tantalum niobate (Na{sub 0.5}K{sub 0.5}Ta{sub 0.5}O{sub 3}, NKTN) were deposited on single crystal [1 0 0] lanthanum aluminate and [1 0 0] MgO substrates (NKT and NKN) and biaxially textured metal substrates via the chemical solution deposition technique. Epitaxial growth of thin-films of NKT, NKN and NKTN was observed on LAO and Ni-5% W. Epitaxial growth of thin-films of NKN and the growth of c-axis aligned thin-films of NKT was observed on MgO. Nanoparticles of SBT, SBN, NKT and NKN were synthesized in reverse micelles from alkoxide precursor solutions. X-ray diffraction and transmission electron

  3. Synthesis and characterization of sodium alkoxides

    Indian Academy of Sciences (India)

    These compounds were characterized using X-ray diffraction technique and IR spectroscopy. The elemental analysis was carried out by CHNS analyser and atomic emission spectroscopy. Normal chain sodium alkoxides were found to exhibit tetragonal crystal structure. Crystal structures of sodium ethoxide and sodium ...

  4. Aggregation and hydrolysis reactions of bismuth alkoxides

    International Nuclear Information System (INIS)

    Whitmire, K.H.; Jones, C.M.; Burkart, M.D.; Hutchinson, J.C.; McKnight, A.L.

    1992-01-01

    This paper reports that new bismuth alkoxide and oxo-alkoxide complexes have been prepared from the salt metathesis reaction of NaOR with BiCl 3 . When R = CH(CF 3 ) 2 , the product is [Bi(μ-OR)(OR) 2 (THF)] 2 . similar work with R = C 6 F 5 has not yielded a simple alkoxide, but complexes of formulation NaBi 3 (μ 3 -O)(OR) 8 (THF), NaBi 4 (μ 3 -O) 2 (OR) 9 (THF) 2 , Na 2 Bi 4 (μ 3 -O) 2 (OR) 10 and Bi 6 (μ 3 -OR)(μ 3 -O) 4 [μ 3 -OBI(OR) 4 ] 3 have been observed. The reaction of BiPh 3 with HOC 6 F 5 , however, did produce the desired alkoxide which has been characterized as [Bi(OR) 2 (μ-OR)(toluene)] 2 and [Bi(OR) 2 (μ-OR)(toluene)] 2 · 2 toluene. The reaction of this alkoxide with NaOC 6 F 5 led to the production of Bi 6 (μ 3 -O) 2 (μ 4 -O)(OR) 12 and NaBi 3 (μ 3 -O)(OR) 8 (THF) 3 . Reaction of BiPh 3 with HOC 6 F 5 in THF led to the formation of Bi 6 (μ 3 -OR)(μ 3 -O) 4 [μ 3 -OBi(OR) 4 ] 3 (THF) 2 . Surprisingly the reaction of BiEt 3 and HOR (R = C 6 F 5 or Ph) displaced only one Et group to give [Et 2 Bi(μ-OR)] oo which exist as infinite chain polymers with alternating Bi-O-Bi backbones. These spiral chains form chiral helices in the crystal lattice. The discovery of high T C superconducting copper oxide phases containing bismuth, lead and thallium has led to this investigation

  5. Preparation of oxide materials from metal alkoxides

    International Nuclear Information System (INIS)

    Turevskaya, E.P.; Turova, N.Ya.; Yanovskaya, M.I.

    2000-01-01

    The results of studies on the sol-gel technologies on the basis of alkoxides are presented. The synthesis and properties of titanates zirconates, niobates, tantalates, vanadates and solid solutions on the basis of Mo, W and Bi oxides, iron oxides and high-temperature superconductors are presented. The most important aspects, determining the choice of optimal conditions for preparation of oxides of concrete compositions with required properties are pointed out. Accomplishment of the whole chain of studies made it possible to synthesize a broad range of metal alkoxides and study their properties and also carry out large-scale studies on preparation of various oxides and materials on the basis thereof, using the source base of the sol-gel method [ru

  6. Direct synthesis of some significant metal alkoxides

    International Nuclear Information System (INIS)

    Emilio, Gule Buyu

    1998-11-01

    Investigations were carried out with an attempt to study direct synthesis of metal alkoxides from elemental metals and appropriate alcohols. These were done by reacting representative metals of group I, II, III 7 IV (which are Na, Mg, Al and Sn respectively) directly with dry ethanol and dry isopropanol. The products were then analysed by infrared spectrophotometer to meter to identify metal alkoxides formed. Ethanol was found to have more acidic character in reactions with these metals than isopropanol, thus its reactions with the metals were faster. Reduction in the acidic character of isopropanol, a secondary alcohol, could be due to the existence off more alkyl groups in the molecule which displays +1 inductive effect. For the same alcohol the metals reactions were found to decrease with increase in electronegativity of the metals. Sodium being the least electronegative metal reacted fasted while tin the more electronegative metal reacted slowest. Mg, Al and Sn required a catalyst,, mercury (II) chloride and heat in order to initiate and drive the reactions completion. The alkoxides formed were found to be soluble to a certain extent in the tow alcohols and the order of solubility is such that Sn≥ Al ≥ Mg ≥ Na.(Author)

  7. Water-soluble titanium alkoxide material

    Science.gov (United States)

    Boyle, Timothy J.

    2010-06-22

    A water soluble, water stable, titanium alkoxide composition represented by the chemical formula (OC.sub.6H.sub.6N).sub.2Ti(OC.sub.6H.sub.2(CH.sub.2N(CH.sub.3).sub.2).sub- .3-2,4,6).sub.2 with a theoretical molecular weight of 792.8 and an elemental composition of 63.6% C, 8.1% H, 14.1% N, 8.1% O and 6.0% Ti.

  8. All-alkoxide synthesis of strontium-containing metal oxides

    Science.gov (United States)

    Boyle, Timothy J.

    2001-01-01

    A method for making strontium-containing metal-oxide ceramic thin films from a precursor liquid by mixing a strontium neo-pentoxide dissolved in an amine solvent and at least one metal alkoxide dissolved in a solvent, said at least one metal alkoxide selected from the group consisting of alkoxides of calcium, barium, bismuth, cadmium, lead, titanium, tantalum, hafnium, tungsten, niobium, zirconium, yttrium, lanthanum, antimony, chromium and thallium, depositing a thin film of the precursor liquid on a substrate, and heating the thin film in the presence of oxygen at between 550 and 700.degree. C.

  9. Hydrolytic activity of -alkoxide/acetato-bridged binuclear Cu (II ...

    Indian Academy of Sciences (India)

    Two -alkoxide/acetate-bridged small molecule binuclear copper(II) complexes were synthesized, and used to promote the hydrolysis of a classic carboxylic acid ester, -nitrophenyl picolinate (PNPP). Both binuclear complexes exhibited good hydrolytic reactivity, giving rise to . 15547- and 17462-fold acceleration over ...

  10. Preparation of titanium diboride powders from titanium alkoxide and ...

    Indian Academy of Sciences (India)

    Administrator

    esting engineering ceramic material which can be used as ballistic armor ... such as metal oxides and ceramics. In the process, reactive metal precursors were initially hydrolyzed, followed by condensation and polymerization reactions. Metal alkoxides are metal- .... bide was studied. Process parameters were optimized to.

  11. Aluminium(III) alkoxides as unique synthons for heterocyclic ...

    Indian Academy of Sciences (India)

    Administrator

    Facile reactivity of aluminium(III) alkoxides with organic protic reagents with alcohol as the only side product provides a convenient method for the synthesis of a variety of products which may not be synthesized by any other route. The possibility of removal of alcohol azeotropically with solvent benzene makes it possible to ...

  12. Standard molar enthalpies of formation of sodium alkoxides

    International Nuclear Information System (INIS)

    Chandran, K.; Srinivasan, T.G.; Gopalan, A.; Ganesan, V.

    2007-01-01

    The molar enthalpies of solution of sodium in methanol, ethanol, and n-propanol and of sodium alkoxides in their corresponding alcohols were measured at T=298.15K using an isoperibol solution calorimeter. From these results and other auxiliary data, the standard molar enthalpies of formation, Δ f H m o (RONa,cr) of sodium methoxide, sodium ethoxide, and sodium n-propoxide were calculated and found to be {(-366.21+/-1.38) (-413.39+/-1.45), and (-441.57+/-1.18)}kJ.mol -1 , respectively. A linear correlation has been found between Δ f H m o (RONa)andΔ f H m o (ROH) for R=n-alkyl, enabling the prediction of data for other sodium alkoxides

  13. Alkoxide-based precursors for direct electrospinning of alumina fibers

    Science.gov (United States)

    Maneeratana, Vasana

    The vision for space exploration in 2004 reinvigorated excitement that was engendered during the 1960's space race. Looking to assist NASA's agency wide mission to develop new technologies to enhance space travel, it is the ultimate goal of this work to support future missions with a hand-held electrospinning apparatus to instantaneously repair existing crucial ceramic fiber structures, such as spacesuits, insulative foams, and tiles. In this research, a new type of precursor is designed based from aluminum alkoxide-based precursors, since alumina serves as a base material for a majority of high-temperature applications. The structure-processing behavior of these precursors is subsequently studied. New precursors of aluminum alkoxides were prepared by modifying solutions; as a result various types of structures were produced, ranging from continuous hollow fibers, continuous solid fibers, or hollow particles. Direct electrospinning with these alkoxide-based precursors yielded an average of 1.9 g/hr of Al2O3, compared to literature with the highest theoretical yield calculated to be 0.68 g/hr. Further exploration of electrospinning parameters found that flow rate directly related to exposure times; therefore fibers were produced in the atmosphere through hydrolysis/condensation with simultaneous solvent evaporation. Furthermore other processing parameters, including the effect of the microstructure due to processing in an electric field were studied. It was found that electrospinning promotes the reaction of the alkoxide, which thereby reduces trapped solvents. As a result of firing schedules, the fibers' hollow features were preserved, and precursors with volatile species resulted in near net shaped fibers. At low firing temperatures, specific surface areas in the range of 330-345 m 2/g were found electrospun fibers. Additionally modified precursors lowered alpha transitions of fibers down to ˜900°C.

  14. Metal alkoxides as starting materials for hydrolysis processes

    International Nuclear Information System (INIS)

    Mukhtar, Omaima Awad

    1999-12-01

    In this thesis the preparation of some metal alkoxides and their hydrolysis products were studied. The characteristic of each prepared alkoxides and their hydrolyzates were determined. Tetra ethoxysilane was prepared by the elemental route (the reaction of silicon powder with liquid ethanol) in the presence of tin ethoxide as a catalyst. The use of tin alkoxide is considered one of the most developed ways used recently in chemistry, compared to the usage of acids and bases as catalyst previously. It had been confirmed by the usage of (infrared) IR spectroscopy, the structure of the prepared material. Also tin isopropoxide had been prepared and hydrolyzed. Ethoxides of aluminium, magnesium and tin had been prepared by the elemental route. The gelation product had been analyzed. tetraethoxysilane had been also prepared by the halosilane route. Isopropoxide of each aluminium, magnesium and tin had been synthesized, hydrolyzed, allowed to gel and analyzed by IR (infrared) spectroscopy and gas-liquid chromatography. However, results obtained indicated that tin ethoxide is an effective catalyst in the direct synthesis of tetraethoxysilane from silicon powder and liquid ethanol. Gas-liquid chromatography, infra-red (IR) analysis showed that the final reaction product was tetraethoxysilane. (Author)

  15. Alkoxide-based magnesium electrolyte compositions for magnesium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Sun, Xiao-Guang; Liao, Chen; Guo, Bingkun

    2018-01-30

    Alkoxide magnesium halide compounds having the formula: RO--Mg--X (1) wherein R is a saturated or unsaturated hydrocarbon group that is unsubstituted, or alternatively, substituted with one or more heteroatom linkers and/or one or more heteroatom-containing groups comprising at least one heteroatom selected from fluorine, nitrogen, oxygen, sulfur, and silicon; and X is a halide atom. Also described are electrolyte compositions containing a compound of Formula (1) in a suitable polar aprotic or ionic solvent, as well as magnesium batteries in which such electrolytes are incorporated.

  16. Alcohol-free alkoxide process for containing nuclear waste

    Science.gov (United States)

    Pope, James M.; Lahoda, Edward J.

    1984-01-01

    Disclosed is a method of containing nuclear waste. A composition is first prepared of about 25 to about 80%, calculated as SiO.sub.2, of a partially hydrolyzed silicon compound, up to about 30%, calculated as metal oxide, of a partially hydrolyzed aluminum or calcium compound, about 5 to about 20%, calculated as metal oxide, of a partially hydrolyzed boron or calcium compound, about 3 to about 25%, calculated as metal oxide, of a partially hydrolyzed sodium, potassium or lithium compound, an alcohol in a weight ratio to hydrolyzed alkoxide of about 1.5 to about 3% and sufficient water to remove at least 99% of the alcohol as an azeotrope. The azeotrope is boiled off and up to about 40%, based on solids in the product, of the nuclear waste, is mixed into the composition. The mixture is evaporated to about 25 to about 45% solids and is melted and cooled.

  17. Characterisation of a new alkoxide sol-gel hydroxyapatite

    International Nuclear Information System (INIS)

    Green, D.D.; Kannangara, G.S.K.; Milev, A.; Ben-Nissan, B.

    1999-01-01

    Hydroxyapatite (HAp) coatings have been used to promote bone growth and fixation towards implant surfaces to encourage faster recovery times for the recipient. Current coating processing techniques, capable of producing thin HAp layers are pulsed-laser deposition and sputtering (high-temperature processing). Other technologies are in vitro methods, electrodeposition and sol-gel, due to the fact that these techniques utilise lower processing temperatures they avoid structural instabilities of HAp at elevated temperatures. The term sol-gel encompasses any process of producing ceramic materials (single and mixed oxides, as well as non-oxides e.g. nitrides) from solutions. The sol-gel process was first identified by Ebelman, and has been used to produce ceramic powders, coatings, and bulk materials including glasses. The implementation of a sol-gel methodology enables increased stoichiometry and homogeneity, while having the ability to coat complex shapes. Sol-gel hydroxyapatite reported by Chai et al. employed tri ethyl phosphite [ P(OEt) 3 ] as the staring phosphorus alkoxide precursor, whereby it was established that in order to obtain monophasic hydroxyapatite upon firing there must be a 24 hour ripening period. The ripening period was determined to be an equilibrium step whereby the equilibrium intermediate phase lied in favour of a diethyl phosphite arrangement (species) within the sol. Therefore, the work here under taken was to produce hydroxyapatite using diethyl phosphite [HOP(OEt) 2 ] as a starting alkoxide precursor with a final aim to reduce or eliminate the ageing period as observed by Chai et al in P(OEt) 3 solutions

  18. Multidentate Fluorinated Alkoxide Ligand Platforms for Oxophilic Metal Centers: From MOCVD Source Reagents to Polymerization Catalysts

    OpenAIRE

    Carpentier, Jean-François

    2010-01-01

    International audience; In contrast to simple fluorinated alkoxides, the coordination chemistry of multidentate ligands that incorporate OC(CF3)2CR2-type moieties and additional donors (N, O, etc.) has been briefly investigated. In this Perspective, we review some well-defined, unambiguously authenticated main group and transition metal complexes supported by multidentate fluorinated alkoxide ligands and we present aspects of their syntheses, structures, and reactivities. The first part is de...

  19. Influence of chelation ratio of metal alkoxides on aging of PZT 53/47 ...

    Indian Academy of Sciences (India)

    Administrator

    GDL-Ameca km 45.5, CP 46600 Ameca, Jalisco, Mexico. MS received 21 September 2013. Abstract. The high reactivity of metal alkoxides, common starting reagents in sol–gel-based synthesis routes, generally demands the use of chelating agents in order to avoid fast hydrolysis and also to allow an easier manipulation of ...

  20. Modification of zirconium and hafnium alkoxides : the effect of molecular structure on derived materials

    NARCIS (Netherlands)

    Spijksma, G.I.

    2006-01-01

    This thesis deals with the influence of modifying ligands on the structure and stability of zirconium and hafnium precursors. The applicability of the obtained modified alkoxides has been evaluated for MOCVD and sol-gel. Furthermore, the influence of the introduction of heteroligands on the sol-gel

  1. Nanostructure Development in Alkoxide-Carboxylate-Derived Precursor Films of Barium Titanate

    NARCIS (Netherlands)

    Stawski, Tomasz; Veldhuis, Sjoerd; Besselink, R.; Castricum, H.L.; Portale, G.; Blank, David H.A.; ten Elshof, Johan E.

    2012-01-01

    The structural evolution in wet alkoxide-carboxylate sol–gel precursor films of barium titanate upon drying was investigated by time-resolved small-angle X-ray scattering (SAXS). The morphology of as-dried amorphous precursor thin films was investigated by transmission electron microscopy (TEM) and

  2. Hydrolytic activity of μ-alkoxide/acetato-bridged binuclear Cu(II ...

    Indian Academy of Sciences (India)

    Abstract. Two μ-alkoxide/acetate-bridged small molecule binuclear copper(II) complexes were synthesized, and used to promote the hydrolysis of a classic carboxylic acid ester, p-nitrophenyl picolinate (PNPP). Both binuclear complexes exhibited good hydrolytic reactivity, giving rise to ca. 15547- and 17462-fold ...

  3. The preparation of lithium aluminate by the hydrolysis of lithium and aluminum alkoxides

    International Nuclear Information System (INIS)

    Turner, C.W.; Clatworthy, B.C.; Gin, A.Y.H.

    1987-10-01

    Lithium aluminate was prepared by heating the hydrolysis products from various combinations of lithium and aluminum alkoxides under an atmosphere of nitrogen. The product was β-LiA1O 2 when aluminum iso-propoxide was a starting material, whereas γ-LiA1O 2 was the product for preparations starting with aluminum n-butoxide. The results were independent of the choice of lithium alkoxide. The hydrolysis of aluminum sec-butoxide with a solution of LiOH led to the γ phase as well. The temperature at which the γ phase developed depended upon the conditions of the hydrolysis reaction and was observed at a temperature as low as 550 degrees Celcius

  4. Multidentate fluorinated alkoxide ligand platforms for oxophilic metal centers: from MOCVD source reagents to polymerization catalysts.

    Science.gov (United States)

    Carpentier, Jean-François

    2010-01-07

    In contrast to simple fluorinated alkoxides, the coordination chemistry of multidentate ligands that incorporate OC(CF(3))(2)CR(2)-type moieties and additional donors (N, O, etc.) has been briefly investigated. In this Perspective, we review some well-defined, unambiguously authenticated main group and transition metal complexes supported by multidentate fluorinated alkoxide ligands and we present aspects of their syntheses, structures, and reactivities. The first part is devoted to the first syntheses of fluorinated alkoxy-imino and fluorinated alkoxy-amino ligand platforms and their application in the preparation of late transition (Ru, Co, Ir, Ni, Pd, Cu) and main group (Sr, Ba, Ga) metal complexes, many of which have been used as chemical vapor deposition (CVD) source reagents. In the second part, heteroleptic complexes based on oxophilic metals (Y, La, Ti, Zr, Hf, Al) and the catalytic performance of these systems in olefin polymerization and ring-opening polymerization (ROP) of cyclic esters are highlighted.

  5. The Obtaining of Nano Oxide Systems SiO2-REE with Alkoxide Technology

    Science.gov (United States)

    Amelina, Anna; Grinberg, Evgenii

    A lot of oxides systems with REE as dopants are used in catalytic processes in organic synthesis. They are very perspectives as thermostable coating in aerospace technics. These systems are usually based on silicon or aluminium oxides and doped with rare-earth elements. This systems can be produced by different methods. One of the most perspective of them is “sol-gel”-method with silicium, aluminium and rare-earth alkoxides as a precursor of doped silica and alumina, or their derivatives. Thus the obtaining of composite SiO _{2} - REE oxide materials by the hydrolysis doped with rare-earth elements was suggested. Some of alcoholate derivatives such as El(OR)n were used in this processes. The SiO _{2}- REE oxides were precipitated during the sol-gel process, where tetraethoxysilane (TEOS) as used as SiO _{2} sources. Also it is known that alkoxides of alkali metals, including lithium alkoxides, are widely used in industry and synthetic chemistry, as well as a source of lithium in various mixed oxide compositions, such as lithium niobate, lithium tantalate or lithium silicate. Therefore, we attempted to obtain the lithium silicate, which is also doped with rare-earth elements. Lithium silicate was obtained by alkaline hydrolysis of tetraethoxysilane with lithium alkoxide. Lithium alkoxide were synthesized by dissolving at metal in the corresponding alcohol are examined. The dependence of the rate of dissolving of the metal on the method of mixing of the reaction mixture and the degree of metal dispersion was investigated. The mathematical model of the process was composed and also optimization of process was carried out. Some oxide SiO _{2}, Al _{2}O _{3} and rare-earth nanostructured systems were obtained by sol-gel-method. The size of particle was determined by electron and X-ray spectroscopy and was in the range of 5 - 15 nm. Purity of this oxide examples for contaminating of heavy metals consists n.(1E-4...1E-5) wt%. Sols obtained by this method may be used

  6. Applications versus properties of Mg–Al layered double hydroxides provided by their syntheses methods: Alkoxide and alkoxide-free sol–gel syntheses and hydrothermal precipitation

    KAUST Repository

    Chubar, Natalia

    2013-12-01

    A tremendous number of studies have examined layered double hydroxides (LDH) for their technological applications in the ion exchange removal of toxic ions, recovery of valuable substances, catalysis, CO2 capture, as a layered host for storage/delivery of biologically active molecules, additives to plastics and building materials, and other functions. Numerous publications always conclude that the materials (prepared, as a rule, using the oldest synthesis method) are very promising for each investigated application; however, the main chemical industries producing these materials advertise them mainly (or only) as plastic additives. The authors performed extensive research using many of the appropriate methods to compare the structure, surface and adsorptive properties of three Mg-Al LHDs produced by advanced synthesis methods. One industrial sample (by Sasol, Germany) prepared by the alkoxide sol-gel method and two novel Mg-Al LDHs synthesised in-house by alkoxide-free sol-gel and hydrothermal precipitation approaches were investigated. Reasons for the very different adsorptive selectivity of the three LDHs towards arsenate, selenate, phosphate, arsenite and selenite have been provided, highlighting the role of speciation of the interlayer carbonate, aluminium, magnesium, interlayer hydration and moisture content in the adsorptive selectivity towards each toxic anion. This work is the first report presenting the regularities of the LDHs structure, surface and anion exchange properties as a function of their syntheses method. It establishes the links to potential technological applications of each investigated LDH and explains the necessary properties required to make the technological application cost-effective and efficient. The paper might accelerate industrial applications of these advanced materials. © 2013 Elsevier B.V.

  7. Preparation and characterization of uranium alkoxides through oxidation of uranium metal

    International Nuclear Information System (INIS)

    Gordon, P.L.; Sauer, N.N.; Burns, C.J.; Watkin, J.G.; Van Der Sluys, W.G.

    1993-01-01

    Currently the authors are investigating the preparation of halide-containing uranium alkoxides by simultaneous halogen and alcohol oxidation of uranium metal. They recently reported the formation of U 2 I 4 (O-i-Pr) 4 (HO-i-Pr) 2 which upon addition of excess isopropanol forms UI 2 (O-i-Pr) 2 (HO-i-Pr) 2 . They report further characterization and reactivity for this monomeric species. Attempts to prepare similar complexes are being made using chlorine gas in the presence of other alcohols. They describe this ongoing research

  8. On the hydrolytic stability of organic ligands in Al-, Ti- and Zr-alkoxide complexes

    OpenAIRE

    Hoebbel, Dagobert; Reinert, Thomas; Schmidt, Helmut K.; Arpac, Ertugrul

    1997-01-01

    The complexation degrees of Al-, Ti- and Zr-butoxide (M) with unsaturated and saturated β-diketones (3-allylpentane-2.4-dione-APD, acetylacetone-ACAC) and β-ketoesters (methacryloxyethyl-acetoacetate-MEAA, allylacetoacetate-AAA, ethylacetoacetate-EAA) as organic ligands (L) were examined by IR and 13C NMR spectroscopy and were found to be L : M ≥ 1.5. The hydrolytic stability of the ligands of the metal alkoxide complexes (L : M = 1) during hydrolysis/condensation reactions at th...

  9. Davis-Beirut Reaction: Alkoxide versus Hydroxide Addition to the Key o-Nitrosoimine Intermediate.

    Science.gov (United States)

    Zhu, Jie S; Duong, Matthew R; Teuthorn, Andrew P; Lu, Julia Y; Son, Jung-Ho; Haddadin, Makhluf J; Kurth, Mark J

    2018-03-02

    Reaction options, alkoxide vs hydroxide vs amine addition to the key intermediate (o-nitrosoimine) generated in the Davis-Beirut reaction of an o-nitrobenzylamine substrate, are reported to explain the nucleophilic addition selectivity of this one-pot indazole-forming process. The hydroxide addition/deprotection pathway as well as the fate of the resulting o-nitrosobenzaldehyde were both uncovered with several o-nitrobenzylamine substrates, and design elements required for an efficient double Davis-Beirut reaction, inspired by new mechanistic insights, were defined.

  10. Production of dispersed nanometer sized YAG powders from alkoxide, nitrate and chloride precursors and spark plasma sintering to transparency

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, M., E-mail: m.suarez@cinn.e [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fernandez, A. [Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L.; Torrecillas, R. [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-03-18

    Yttrium aluminum garnet (YAG) was synthesized from different starting materials, i.e., alkoxide, nitrate and chloride precursors. The conversion steps from the precursors to crystalline YAG were studied by Raman spectroscopy. Dispersed YAG powders were formed at a relatively low temperature, around 800 {sup o}C by the chlorides route, whereas alkoxide precursors needed firing over 900 {sup o}C and nitrates even over 1100 {sup o}C. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 {sup o}C with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  11. Production of dispersed nanometer sized YAG powders from alkoxide, nitrate and chloride precursors and spark plasma sintering to transparency

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Torrecillas, R.

    2010-01-01

    Yttrium aluminum garnet (YAG) was synthesized from different starting materials, i.e., alkoxide, nitrate and chloride precursors. The conversion steps from the precursors to crystalline YAG were studied by Raman spectroscopy. Dispersed YAG powders were formed at a relatively low temperature, around 800 o C by the chlorides route, whereas alkoxide precursors needed firing over 900 o C and nitrates even over 1100 o C. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 o C with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  12. Effect of concentrations of plasticizers on the sol-gel properties developed from alkoxides precursors

    Energy Technology Data Exchange (ETDEWEB)

    Kunst, Sandra Raquel; Longhi, Marielen; Zini, Lucas Pandolphi [Universidade de Caxias do Sul (CCET/UCS), Caxias do Sul, RS (Brazil). Centro de Ciências Exatas e Tecnologia; Beltrami, Lilian Vanessa Rossa; Boniatti, Rosiana; Cardoso, Henrique Ribeiro Piaggio; Vega, Maria Rita Ortega; Malfatti, Célia de Fraga, E-mail: lvrossa@yahoo.com.br [Universidade Federal do Rio Grande do Sul (LAPEC/UFRGS), Porto Alegre, RS (Brazil). Laboratorio de Pesquisa em Corrosão

    2017-07-01

    Coatings developed through sol-gel method is presented as an interesting replacement to chromium coating. Sol-gel method present advantages as high purity and excellent distribution of the components. The objective of this work is to synthesize and characterize a film obtained by sol-gel route. The film was prepared with 3-(trimethoxysilylpropyl) methacrylate (TMSPMA), tetraethoxysilane (TEOS) and cerium nitrate, using water and ethanol as solvents. Polyethyleneglycol (PEG) plasticizer was added at four different concentrations. The sol was characterized by techniques of viscosity, thermogravimetric analysis (TGA), X-ray diffraction (XRD) nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that tetrafunctional alkoxides condensation was retarded by the plasticizer, forming a compact film. The film with 20 g.L-1 of PEG showed the best electrochemical behavior. (author)

  13. NMR and IR spectroscopic examination of the hydrolytic stability of organic ligands in metal alkoxide complexes and of oxygen bridged heterometal bonds

    OpenAIRE

    Hoebbel, Dagobert; Reinert, Thomas; Schmidt, Helmut K.

    1996-01-01

    IR and 13C NMR investigations of the hydrolytic stabilites of the saturated and unsaturated beta-keto ligands acetylacetone (ACAC), ethylacetoacetate (EAA), allylacetoacetate (AAA), methacryloxyethyl-acetoacetate (MEAA) of the Al-, Ti- and Zr-butoxide complexes show a strong dependence on the type of the metal alkoxide and the structure of the organic ligands. The hydrolytic stabilities of the ligands decrease in the order Al-Zr-Ti-alkoxide and ACAC>AAA>EAA>=MEAA. Sol-gel reactions of complex...

  14. Different mechanisms at different temperatures for the ring-opening polymerization of lactide catalyzed by binuclear magnesium and zinc alkoxides.

    Science.gov (United States)

    Sun, Yangyang; Cui, Yaqin; Xiong, Jiao; Dai, Zhongran; Tang, Ning; Wu, Jincai

    2015-10-07

    Two binuclear magnesium and zinc alkoxides supported by a bis-salalen type dinucleating heptadentate Schiff base ligand were synthesized and fully characterized. The two complexes are efficient initiators for the ring-opening polymerization (ROP) of L-lactide, affording polymers with narrow polydispersities and desirable molecular weights. Interestingly, the mechanisms for the ROP of lactide are different at different temperatures. At a high temperature of 130 °C, a coordination-insertion mechanism is reasonable for the bulk melt polymerization of lactide. At a low temperature, the alkoxide cannot initiate the ROP reaction; however, upon the addition of external benzyl alcohol into the system, the ROP of lactide can smoothly proceed via an "activated monomer" mechanism. In addition, these complexes display slight stereo-selectivity for the ring-opening polymerization of rac-lactide, affording partially isotactic polylactide in toluene with a Pm value of 0.59.

  15. Strong influence of polymer architecture on the microstructural evolution of hafnium-alkoxide-modified silazanes upon ceramization.

    Science.gov (United States)

    Papendorf, Benjamin; Nonnenmacher, Katharina; Ionescu, Emanuel; Kleebe, Hans-Joachim; Riedel, Ralf

    2011-04-04

    The present study focuses on the synthesis and ceramization of novel hafnium-alkoxide-modified silazanes as well as on their microstructure evolution at high temperatures. The synthesis of hafnia-modified polymer-derived SiCN ceramic nanocomposites is performed via chemical modification of a polysilazane and of a cyclotrisilazane, followed by cross-linking and pyrolysis in argon atmosphere. Spectroscopic investigation (i.e., NMR, FTIR, and Raman) shows that the hafnium alkoxide reacts with the N-H groups of the cyclotrisilazane; in the case of polysilazane, reactions of N-H as well as Si-H groups with the alkoxide are observed. Consequently, scanning and transmission electron microscopy studies reveal that the ceramic nanocomposites obtained from cyclotrisilazane and polysilazane exhibited markedly different microstructures, which is a result of the different reaction pathways of the hafnium alkoxide with cyclotrisilazane and with polysilazane. Furthermore, the two prepared ceramic nanocomposites are unexpectedly found to exhibit extremely different high-temperature behavior with respect to decomposition and crystallization; this essential difference is found to be related to the different distribution of hafnium throughout the ceramic network in the two samples. Thus, the homogeneous distribution of hafnium observed in the polysilazane-derived ceramic leads to an enhanced thermal stability with respect to decomposition, whereas the local enrichment of hafnium within the matrix of the cyclotrisilazane-based sample induces a pronounced decomposition upon annealing at high temperatures. The results indicate that the chemistry and architecture of the precursor has a crucial effect on the microstructure of the resulting ceramic material and consequently on its high-temperature behavior. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. STUDY OF THE EFFECT OF MIXED ALKOXIDES OXYPROPYLATED AROMATIC SECONDARY AMINES ON THE STRUCTURE OF DIENE POLYMERS

    Directory of Open Access Journals (Sweden)

    A. V. Firsova

    2014-01-01

    Full Text Available Summary. This article discusses the relationship structure of the diene and styrene-butadiene copolymers (SBR, the structure of the part of the initiating system of n-butyl lithium + modifier, which is a mixed alkoxide of an alkali and alkaline earth metals, which allows to control the microstructure of the diene polymer and its molecular weight characteristics. Alcohol derivatives selected high-boiling alcohols tetra (hydroxypropyl ethylenediamine (lapromol - 294 and tetrahydrofurfuryl alcohol (TGFS. The scheme of obtaining styrene-butadiene random copolymers (SBR with a high content (64 ± 4 % of vinyl units was developed. The process of copolymerization with sodium-calcium-lithium complex Са(С4Н9 2 • С4Н9Na • LiOR was carried out. After water decontamination residues deactivated complex remain in the polymer as a filler. Studied the copolymerization of butadiene with styrene in the presence of lithium amide, which is obtained on the basis of the alcohols containing the group - NH -. With the increasing solubility of the branching alkoxides increases in hydrocarbon solvents. Found that sodium alkoxide hydroxypropyl aniline decane insoluble, the sodium alcoholate hydroxypropyl toluidine soluble in decane. The results of studies of the effect of mixed alkoxides oxypropylated aromatic secondary amines on the structure of diene polymers. The Providing the necessary initiation systems for preparing functionalized polymers. It was revealed that secondary amines from which the lithium amides are inactive, so the polymerization of monomers was carried out in the presence of electron as that used glycol ethers - diglyme, THF, 2,2 - ditetragidrofurfuril propane, which increase polymer-filler interaction. The results of research of the microstructure of the diene part of SBR obtained in the mixed alkali metal alkoxide with a mixture of lapromol alcohols, toluidine and TGFS showed that increasing toluidine consisting of mixed modifier reduces

  17. Thermochromic behavior of vanadium(IV) alkoxides in solution: a molecular modeling approach

    International Nuclear Information System (INIS)

    Freitas, Alexandre C. de; Westrup, Katia C. M.; Nunes, Giovana G.; Gulin, Denis J.; Haiduke, Roberto L. A.; Soares, Jaisa F.; Sa, Eduardo L. de

    2010-01-01

    The thermochromic behavior exhibited by vanadium(IV) alkoxides, [V 2 (mu-OPr i ) 2 (OPr i ) 6 ] and [V 2 (m-ONep) 2 (ONep) 6 ], OPr i = isopropoxide and ONep = neopentoxide, was studied by molecular modeling using DFT, TDDFT and INDO/S methods. The vibrational and electronic spectra calculated for [V 2 (mu-OPr i ) 2 (OPr i ) 6 ] were very similar to the experimental data registered for crystalline samples of the complex and for its solutions at low temperature ( 315 K) were compatible with those calculated for the monomeric form, [V(OPr i ) 4 ]. These results consistently point to a monomer/dimer equilibrium as an explanation for the solution thermochromism of {V(OPr i )-4} n . In spite of the structural similarity between [V 2 (mu-ONep) 2 (ONep) 6 ] and [V 2 (mu-OPr i ) 2 (OPr i ) 6 ] in the solid state, the thermochromic behavior of the former could not be explained by the same model, and the possibility of tetranuclear aggregation at low temperatures was also investigated. (author)

  18. Process Development in the Preparation and Characterization of Silicon Alkoxide From Rice Husk

    International Nuclear Information System (INIS)

    Khin San Win; Toe Shein; Nyunt Wynn

    2011-12-01

    The preparation and characterization of silicon alkoxide (silicon isopropoxide) from rice husk char has been studied. In the investigation, four kinds of Myanmar paddies were chemically assayed. Analyses showed the silicon contend varies from 73-92% . Based on the silicon content, the process development in the production of silicon isopropoxide was carried out. In the process development, silicon isopropoxide with a yield of 44.21% was achieved by the direct reaction of isopropanol in situ by silicon tetrachloride, which was directly produced by the chlorination of rice husk char at the high temperature range of 900-1100 C. The novelity of the process was that, silicon isopropoxide was achieved in situ and not by using the old process, where generally isopropanol was reacted with silicon tetrachloride. The physiochemical properties of silicon isopropoxide was confirmed by conventional and modern techniques. In the investigation, the starting materials, silica in the reaction products were characterized, identified and confirmed by modren techniques. Silicon isopropoxide can be a sources of pore silica whereby silicon of 97-99% of purity can be achieved.

  19. Characterization of amorphous yttria layers deposited by aqueous solutions of Y-chelate alkoxides complex

    Science.gov (United States)

    Kim, Young-Soon; Lee, Yu-Ri; Kim, Byeong-Joo; Lee, Jae-Hun; Moon, Seung-Hyun; Lee, Hunju

    2015-01-01

    Crack-free amorphous yttria layers were deposited by dip coating in solutions of different Y-chelate alkoxides complex. Three Y-chelate solutions of different concentrations were prepared using yttrium acetate tetrahydrate, yttrium stearic acid as Y source materials. PEG, diethanolamine were used as chelating agents, while ethanol, methanol and tetradecane were used as solvent. Three different combinations of chelating and solvents were used to prepare solutions for Y2O3 dip coating on SUS, electropolished and non-electropolished Hastelloy C-276 substrates. The thickness of the films was varied by changing the number of dipping cycles. At an optimized condition, the substrate surface roughness (rms) value was reduced from ∼50 nm to ∼1 nm over a 10 × 10 μm2 area. After Y2O3 deposition, MgO was deposited using ion-beam assisted deposition (IBAD), then LaMnO3 (LMO) was deposited using sputtering and GdBCO was deposited using reactive co-evaporation by deposition and reaction (RCE-DR). Detailed X-ray study indicates that LMO/MgO/Y2O3 and GdBCO/LMO/MgO/Y2O3 stack films have good out-of-plane and in-plane textures with strong c-axis alignment. The critical current (Ic) of GdBCO/LMO/MgO/Y2O3 multilayer structure varied from 190 to 420 A/cm with different solutions, when measured at 77 K. These results demonstrated that amorphous yttria can be easily deposited by dip coating using Y-chelates complex as a diffusion barrier and nucleation layer.

  20. Characterization of amorphous yttria layers deposited by aqueous solutions of Y-chelate alkoxides complex

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young-Soon, E-mail: kyscjb@i-sunam.com; Lee, Yu-Ri; Kim, Byeong-Joo; Lee, Jae-Hun; Moon, Seung-Hyun; Lee, Hunju

    2015-01-15

    Highlights: • Economical method for crack-free amorphous yttria layer deposition by dip coating. • Simpler process for planar yttria film as a diffusion barrier and nucleation layer. • Easy control over the film properties with better characteristics. • Easy control over the thickness of the deposited films. • A feasible process that can be easily adopted by HTSCC industries. - Abstract: Crack-free amorphous yttria layers were deposited by dip coating in solutions of different Y-chelate alkoxides complex. Three Y-chelate solutions of different concentrations were prepared using yttrium acetate tetrahydrate, yttrium stearic acid as Y source materials. PEG, diethanolamine were used as chelating agents, while ethanol, methanol and tetradecane were used as solvent. Three different combinations of chelating and solvents were used to prepare solutions for Y{sub 2}O{sub 3} dip coating on SUS, electropolished and non-electropolished Hastelloy C-276 substrates. The thickness of the films was varied by changing the number of dipping cycles. At an optimized condition, the substrate surface roughness (rms) value was reduced from ∼50 nm to ∼1 nm over a 10 × 10 μm{sup 2} area. After Y{sub 2}O{sub 3} deposition, MgO was deposited using ion-beam assisted deposition (IBAD), then LaMnO{sub 3} (LMO) was deposited using sputtering and GdBCO was deposited using reactive co-evaporation by deposition and reaction (RCE-DR). Detailed X-ray study indicates that LMO/MgO/Y{sub 2}O{sub 3} and GdBCO/LMO/MgO/Y{sub 2}O{sub 3} stack films have good out-of-plane and in-plane textures with strong c-axis alignment. The critical current (Ic) of GdBCO/LMO/MgO/Y{sub 2}O{sub 3} multilayer structure varied from 190 to 420 A/cm with different solutions, when measured at 77 K. These results demonstrated that amorphous yttria can be easily deposited by dip coating using Y-chelates complex as a diffusion barrier and nucleation layer.

  1. Multinuclear solid-state high-resolution and C-13 -{Al-27} double-resonance magic-angle spinning NMR studies on aluminum alkoxides

    NARCIS (Netherlands)

    Abraham, A.; Prins, R.; Bokhoven, J.A. van; Eck, E.R.H. van; Kentgens, A.P.M.

    2006-01-01

    A combination of Al-27 magic-angle spinning (MAS)/multiple quantum (MQ)-MAS, C-13-H-1 CPMAS, and C-13-{Al-27} transfer of population in double-resonance (TRAPDOR) nuclear magnetic resonance (NMR) were used for the structural elucidation of the aluminum alkoxides aluminum ethoxide, aluminum

  2. Optical and electrochemical properties of CeO{sub 2} thin film prepared by an alkoxide route

    Energy Technology Data Exchange (ETDEWEB)

    Avellaneda, Cesar O. [Departamento de Quimica - LIEC, Universidade Federal de Sao Carlos, C.P. 676, CEP 13565-905, Sao Carlos, SP (Brazil); Berton, Marcos A.C. [Departamento de Tecnologia de Materiais, Instituto de Tecnologia para o Desenvolvimento - LACTEC, C.P. 19067, CEP 81531-990, Curitiba, PR (Brazil); Bulhoes, Luis O.S. [Departamento de Quimica - LIEC, Universidade Federal de Sao Carlos, C.P. 676, CEP 13565-905, Sao Carlos, SP (Brazil); CENIP, Centro Universitario Central Paulista - UNICEP, Rua Miguel Petroni 5111, CEP 13563-470, Sao Carlos, SP (Brazil)

    2008-02-15

    Transparent CeO{sub 2} thin solid films, used as ion storage layer in electrochromic devices were prepared by the sol-gel method using an alkoxide route combined with the dip-coating technique. The precursor sol was prepared from a mixture of cerium (IV) methoxyethoxide in anhydrous 2-butanol. Electrochemical Li{sup +} intercalation/deintercalation was performed by cyclic voltammetry and the results indicate that the CeO{sub 2}/LiClO{sub 4} system is electrochemically reversible. The total inserted/extracted charge of the CeO{sub 2} film was determined by chronoamperometric measurements, which showed an ion storage capacity of {proportional_to}14 mC/cm{sup 2}. The solid-state diffusion of lithium ion into the CeO{sub 2} thin films was investigated by electrochemical impedance spectroscopy. (author)

  3. Effect of Ligand Field Tuning on the SMM Behavior for Three Related Alkoxide-Bridged Dysprosium Dimers.

    Science.gov (United States)

    Peng, Yan; Mereacre, Valeriu; Baniodeh, Amer; Lan, Yanhua; Schlageter, Martin; Kostakis, George E; Powell, Annie K

    2016-01-04

    The synthesis and characterization of three Dy2 compounds, [Dy2(HL1)2(NO3)4] (1), [Dy2(L2)2(NO3)4] (2), and [Dy2(HL3)2(NO3)4] (3), formed using related tripodal ligands with a central tertiary amine bearing picolyl and alkoxy arms, 2-[(2-hydroxy-ethyl)-pyridin-2-ylmethylamino]-ethanol (H2L1), 2-(bis-pyridin-2-ylmethylamino)-ethanol (HL2), and 2-(bis-pyridin-2-ylmethylamino)-propane-1,3-diol (H2L3), are reported. The compounds are rare examples of alkoxide-bridged {Dy2} complexes and display capped square antiprism coordination geometry around each Dy(III) ion. Changes in the ligand field environment around the Dy(III) ions brought about through variations in the ligand donors can be gauged from the magnetic properties, with compounds 1 and 2 showing antiparallel coupling between the Dy(III) ions and 3 showing parallel coupling. Furthermore, slow relaxation of the magnetization typical of SMM behavior could be observed for compounds 2 and 3, suggesting that small variations in the ligand field can have a significant influence on the slow relaxation processes responsible for SMM behavior of Dy(III)-based systems.

  4. Quantifying the Sigma and Pi interactions between U(V) f orbitals and halide, alkyl, alkoxide, amide and ketimide ligands

    Energy Technology Data Exchange (ETDEWEB)

    University of California, Berkeley; Lukens, Wayne W.; Edelstein, Norman M.; Magnani, Nicola; Hayton, Trevor W.; Fortier, Skye; Seaman, Lani A.

    2013-06-20

    f Orbital bonding in actinide and lanthanide complexes is critical to their behavior in a variety of areas from separations to magnetic properties. Octahedral f1 hexahalide complexes have been extensively used to study f orbital bonding due to their simple electronic structure and extensive spectroscopic characterization. The recent expansion of this family to include alkyl, alkoxide, amide, and ketimide ligands presents the opportunity to extend this study to a wider variety of ligands. To better understand f orbital bonding in these complexes, the existing molecular orbital (MO) model was refined to include the effect of covalency on spin orbit coupling in addition to its effect on orbital angular momentum (orbital reduction). The new MO model as well as the existing MO model and the crystal field (CF) model were applied to the octahedral f1 complexes to determine the covalency and strengths of the ? and ? bonds formed by the f orbitals. When covalency is significant, MO models more precisely determined the strengths of the bonds derived from the f orbitals; however, when covalency was small, the CF model was better than either MO model. The covalency determined using the new MO model is in better agreement with both experiment and theory than that predicted by the existing MO model. The results emphasize the role played by the orbital energy in determining the strength and covalency of bonds formed by the f orbitals.

  5. Preparation of Bragg mirrors on silica optical fibers and inner walls of silica capillaries by employing the sol-gel method, and titanium and silicon alkoxides

    Czech Academy of Sciences Publication Activity Database

    Bartoň, Ivo; Matějec, Vlastimil; Mrázek, Jan; Podrazký, Ondřej; Matoušek, J.

    2017-01-01

    Roč. 81, č. 3 (2017), s. 867-879 ISSN 0928-0707 R&D Projects: GA ČR GA16-10019S Grant - others:AV ČR(CZ) SAV-16-17 Program:Bilaterální spolupráce Institutional support: RVO:67985882 Keywords : Multilayered coatings * Silica and titania layersSilica and titania layers * Alkoxide sol–gel method Subject RIV: JA - Electron ics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electron ic engineering Impact factor: 1.575, year: 2016

  6. Preparation of Bragg mirrors on silica optical fibers and inner walls of silica capillaries by employing the sol-gel method, and titanium and silicon alkoxides

    Czech Academy of Sciences Publication Activity Database

    Bartoň, Ivo; Matějec, Vlastimil; Mrázek, Jan; Podrazký, Ondřej; Matoušek, J.

    2017-01-01

    Roč. 81, č. 3 (2017), s. 867-879 ISSN 0928-0707 R&D Projects: GA ČR GA16-10019S Grant - others:AV ČR(CZ) SAV-16-17 Program:Bilaterální spolupráce Institutional support: RVO:67985882 Keywords : Multilayered coatings * Silica and titania layersSilica and titania layers * Alkoxide sol–gel method Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electronic engineering Impact factor: 1.575, year: 2016

  7. Alternating Sequence Controlled Copolymer Synthesis of α-Hydroxy Acids via Syndioselective Ring-Opening Polymerization of O-Carboxyanhydrides Using Zirconium/Hafnium Alkoxide Initiators.

    Science.gov (United States)

    Sun, Yangyang; Jia, Zhaowei; Chen, Changjuan; Cong, Yong; Mao, Xiaoyang; Wu, Jincai

    2017-08-09

    The ring-opening polymerization (ROP) of O-carboxyanhydrides (OCAs) can give diverse poly(α-hydroxy acid)s (PAHAs) with different functional groups because of easy modification of the side group of OCAs, which can extend applications of PAHAs widely. The stereoselective polymerization of O-carboxyanhydrides and further sequence controlled alternating copolymerization of OCAs were still big challenges until now for lack of suitable catalysts/initiators. In this work, a highly syndioselective ROP of OCAs system as the first stereoselective example in this area is reported using zirconium/hafnium alkoxides as initiators with the highest P r value up to 0.95. Furthermore, these initiators were successfully applied in the precisely alternating sequence controlled copolymerization of PheOCA and Tyr(Bn)OCA, and alternating copolymerization of LacOCA and PheOCA was also achieved.

  8. Preparation of Layer-Structured CaBi2Ta2O9 Ferroelectric Thin Films through a Triple Alkoxide Route

    Science.gov (United States)

    Kato, Kazumi; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi

    2000-09-01

    A triple alkoxide solution for CaBi2Ta2O9 (CBT) thin films was prepared. CBT thin films were deposited on Pt-passivated silicon and Pt-passivated quartz glass substrates. The thin films on Pt-passivated silicon crystallized to form the perovskite structure at low temperatures and showed preferred orientation along the c-axis. The thin films did not show ferroelectric P-E hysteresis loops. In contrast, the 750°C-annealed thin film on Pt-passivated quartz glass showed random orientation and exhibited excellent P-E hysteresis loops. The remanent polarization (Pr) and the coercive electric field (Ec) at 13 V were 6.9 μC/cm2 and 170 kV/cm, respectively.

  9. Reactions of aromatic nitro-compounds. LV. Anionic sigma-complexes of sym-trinitrobenzene with the alkoxides of dihydric alcohols

    Energy Technology Data Exchange (ETDEWEB)

    Mel' nikov, A.I.; Gitis, S.S.; Kaminskii, A.Ya.

    1986-12-20

    The reactions of alkoxides of dihydric alcohols with 2,4,6-trinitroanisole and picryl chloride have been studied. The reaction between 2,4,6-trinitroanisole and sodium 2-hydroxyethoxide, 3-hydroxypropoxide, 4-hydroxybutoxide, and 2-methoxyethoxide gives the unsymmetrical 1-methoxy-1-hydroxyalkoxy-2,4,6-trinitrocyclohexa-2,5-dienate sigma-complexes, which are converted on heating into the 1,1-dihydroxyalkoxy-2,4-6-trinitrocyclohexa-2,5-dienate sigma-complexes. In the case of sodium 1-methoxy-1-(..beta..-hydroxyethoxy)-2,4,6-trinitrocyclohexa-2,5-dienate, heating results in intramolecular spirocyclization of the ..beta..-hydroxyethoxy grouping to give sodium 6,8,10-trinitro-1,4-dioxaspiro(4,5)deca-6,9-dienate. The reaction of sodium 3-hydroxy-propoxide, 4-hydroxybutoxide, 2-methoxyethoxide, and diethyleneglycolate with picryl chloride gives the symmetrical 1,1-dihyroxyalkoxy sigma-complexes, while sodium 2-hydroxyethoxide forms a sigma-complex with a 1,3-dioxolane spiro-ring. The composition and structures of the sigma-complexes, isolated as their sodium salts, were established by their elemental analyses and PMR and IR spectroscopy.

  10. New inorganic (an)ion exchangers based on Mg–Al hydrous oxides: (Alkoxide-free) sol–gel synthesis and characterisation

    KAUST Repository

    Chubar, Natalia

    2011-05-01

    New inorganic ion exchangers based on double Mg-Al hydrous oxides were generated via the new non-traditional sol-gel synthesis method which avoids using metal alkoxides as raw materials. Surface chemical and adsorptive properties of the final products were controlled by several ways of hydrogels and xerogels treatments which produced the materials of the layered structure, mixed hydrous oxides or amorphous adsorbents. The final adsorptive materials obtained via thermal treatment of xerogels were the layered mesoporous materials with carbonate in the interlayer space, surface abundance with hydroxylic groups and maximum adsorptive capacity to arsenate. Higher affinity of Mg-Al hydrous oxides towards H2AsO4- is confirmed by steep adsorption isotherms having plateau (removal capacity) at 220. mg[As]. gdw-1 for the best sample at pH = 7, fast adsorption kinetics and little pH effect. Adsorption of arsenite, fluoride, bromate, bromide, selenate, borate by Mg-Al hydrous oxides was few times high either competitive (depending on the anion) as compare with the conventional inorganic ion exchange adsorbents. © 2011 Elsevier Inc.

  11. Thermochromic behavior of vanadium(IV) alkoxides in solution: a molecular modeling approach; Termocromismo em solucoes de alcoxidos de vanadio(IV): uma abordagem pela modelagem molecular

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Alexandre C. de; Westrup, Katia C. M.; Nunes, Giovana G.; Gulin, Denis J.; Haiduke, Roberto L. A.; Soares, Jaisa F.; Sa, Eduardo L. de [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Quimica

    2010-07-01

    The thermochromic behavior exhibited by vanadium(IV) alkoxides, [V{sub 2}(mu-OPr{sup i}){sub 2}(OPr{sup i}){sub 6}] and [V{sub 2}(m-ONep){sub 2}(ONep){sub 6}], OPr{sup i} = isopropoxide and ONep = neopentoxide, was studied by molecular modeling using DFT, TDDFT and INDO/S methods. The vibrational and electronic spectra calculated for [V{sub 2}(mu-OPr{sup i}){sub 2}(OPr{sup i}){sub 6}] were very similar to the experimental data registered for crystalline samples of the complex and for its solutions at low temperature (< 210 K), while spectra recorded at high temperature (> 315 K) were compatible with those calculated for the monomeric form, [V(OPr{sup i}){sub 4}]. These results consistently point to a monomer/dimer equilibrium as an explanation for the solution thermochromism of {l_brace}V(OPr{sup i})-4{r_brace}{sub n}. In spite of the structural similarity between [V{sub 2}(mu-ONep){sub 2}(ONep){sub 6}] and [V{sub 2}(mu-OPr{sup i}){sub 2}(OPr{sup i}){sub 6}] in the solid state, the thermochromic behavior of the former could not be explained by the same model, and the possibility of tetranuclear aggregation at low temperatures was also investigated. (author)

  12. Self-assembled SnO2 micro- and nanosphere-based gas sensor thick films from an alkoxide-derived high purity aqueous colloid precursor

    Science.gov (United States)

    Kelp, G.; Tätte, T.; Pikker, S.; Mändar, H.; Rozhin, A. G.; Rauwel, P.; Vanetsev, A. S.; Gerst, A.; Merisalu, M.; Mäeorg, U.; Natali, M.; Persson, I.; Kessler, V. G.

    2016-03-01

    Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.Tin oxide is considered to be one of the

  13. Termocromismo em soluções de alcóxidos de Vanádio(IV: uma abordagem pela modelagem molecular Thermochromic behavior of vanadium(IV alkoxides in solution: a molecular modeling aproach

    Directory of Open Access Journals (Sweden)

    Alexandre C. de Freitas

    2010-01-01

    Full Text Available The thermochromic behavior exhibited by vanadium(IV alkoxides, [V2(μ-OPr i2(OPr i 6] and [V2(μ-ONep2(ONep6 ], OPr i = isopropoxide and ONep = neopentoxide, was studied by molecular modeling using DFT, TDDFT and INDO/S methods. The vibrational and electronic spectra calculated for [V2(μ-OPr i2(OPr i 6] were very similar to the experimental data registered for crystalline samples of the complex and for its solutions at low temperature ( 315 K were compatible with those calculated for the monomeric form, [V(OPr i4]. These results consistently point to a monomer/dimer equilibrium as an explanation for the solution thermochromism of {V(OPr i4}n. In spite of the structural similarity between [V2(μ-ONep2(ONep6 ] and [V2(μ-OPr i2(OPr i 6] in the solid state, the thermochromic behavior of the former could not be explained by the same model, and the possibility of tetranuclear aggregation at low temperatures was also investigated.

  14. EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions

    KAUST Repository

    Chubar, Natalia

    2014-08-08

    © the Partner Organisations 2014. Current research on Layered Double Hydroxides (LDHs, also known as hydrotalcites, HTs) is predominantly focused on their intercalations, but the industrial application of LDHs for anion exchange adsorption has not yet been achieved. It was recently recognized that, to develop LDH applications, these materials should be produced using methods other than direct co-precipitation. Mg-Al-CO3LDH produced using an alkoxide-free sol-gel synthesis showed exceptional removal properties for aqueous selenium species. Se K-edge EXAFS/XANES and FTIR studies (supporting the data by XRD patterns) were performed to explain the unusual adsorptive performance of Mg-Al LDH by revealing the molecular-level mechanism of HSeO3 -, SeO4 2-and {HSeO3 -+ SeO4 2-} uptake at pH 5, 7 and 8.5. The role of inner-sphere complexation (exhibited by inorganic adsorbents with good performance) in adsorption of both selenium aqueous species was not confirmed. However, Mg-Al LDH fully met the other expectations regarding the involvement of the interlayer anions. The interlayer carbonate (due to its favorable speciation and generous HT hydration) gave a "second breath" to selenite sorption and was the only mechanism that controlled the removal of Se(vi). Because inner sphere complexation was the leading mechanism for selenite removal, ion exchange via surface OH-and interlayer CO3 2-species was the only mechanism for selenate removal; both of these species were easily bound to Mg-Al LDH (on its surface and gently parked into the interlayer forming a multilayer without violation of the structure of Mg-Al-CO3LDH). This work provides the first theoretical explanation of why it is more difficult to sorb selenate than selenite and which material should be used for this purpose. This journal is

  15. Synthesis and characterization of sodium alkoxides

    Indian Academy of Sciences (India)

    Unknown

    Ethanol + 10% H2O. (Mukaibo et al 1978). Japan. OEC, MONJU. Ethanol + 10% H2O. (Nakai et al 1997). UK. Dounreay Nuclear Power Establishment Butyl cellosolve. (Donaldson and Bray 1978). USA. 1. SRDA ..... don: The English Language Book Society and Longman. Group Ltd) 4th ed. Ganesan V, Krishnamoorthy D ...

  16. Synthesis and characterization of sodium alkoxides

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Alcohol route is being adopted for cleaning sodium from sodium-wetted small components of coolant circuits of fast reactors. For better understanding of sodium–alcohol reactions and their energetics, the data on thermo-chemical properties such as heats of sodium–alcohol reactions, heats of dissolution, heat ...

  17. SOLVENT EFFECTS IN THE HYDROXIDE AND ALKOXIDE ...

    African Journals Online (AJOL)

    in purely aqueous medium, methanol and ethanol; and in a series of dioxane- methanol mixtures. The a scale of ... in the rationalization or correlation of solvent effects on reaction rates and activation parameters. ..... R.W. Taft, Jr., in "Ster'ic Effect in Organic Chemistry", M.S. Newman Ed._. Wiley, New York, N."!'., (1985'). I7.

  18. Preparation of titanium diboride powders from titanium alkoxide and ...

    Indian Academy of Sciences (India)

    Administrator

    1⋅3 to 2⋅5. The results indicated that as the TTIP concentration had an important role in gel formation, the reaction temperature and B4C to TTIP molar ratio showed obvious effects on the formation of TiB2. Pure. TiB2 was prepared using molar composition of Ti : B4C = 1 : 2⋅3 and the optimum synthesis temperature was.

  19. Preparation of titanium diboride powders from titanium alkoxide and ...

    Indian Academy of Sciences (India)

    Titanium diboride powders were prepared through a sol–gel and boron carbide reduction route by using TTIP and B4C as titanium and boron sources. The influence of TTIP concentration, reaction temperature and molar ratio of precursors on the synthesis of titanium diboride was investigated. Three different concentrations ...

  20. Applications vs properties of Mg-Al Layered Double Hydroxides provided by their syntheses methods: alkoxide and alkoxide-free sol-gel syntheses and hydrothermal precipitation

    NARCIS (Netherlands)

    Chubar, N.; Gerda, V.; Megantari, O.; Mičušík, M.; Omastova, M.; Heister, K.; Man, P.; Fraissard, J.

    2013-01-01

    A tremendous number of studies have examined layered double hydroxides (LDH) for their technological applications in the ion exchange removal of toxic ions, recovery of valuable substances, catalysis, CO2 capture, as a layered host for storage/delivery of biologically active molecules, additives to

  1. Characterization of Titanium Oxide Nanoparticles Obtained by Hydrolysis Reaction of Ethylene Glycol Solution of Alkoxide

    International Nuclear Information System (INIS)

    Uekawa, N.; Endo, N.; Ishii, K.; Kojima, T.; Kakegawa, K.

    2012-01-01

    Transparent and stable sols of titanium oxide nanoparticles were obtained by heating a mixture of ethylene glycol solution of titanium tetraisopropoxide (TIP) and a NH 3 aqueous solution at 368 K for 24 h. The concentration of NH 3 aqueous solution affected the structure of the obtained titanium oxide nanoparticles. For NH 3 aqueous solution concentrations higher than 0.2 mol/L, a mixture of anatase TiO 2 nanoparticles and layered titanic acid nanoparticles was obtained. The obtained sol was very stable without formation of aggregated precipitates and gels. Coordination of ethylene glycol to Ti4+ ions inhibited the rapid hydrolysis reaction and aggregation of the obtained nanoparticles. The obtained titanium oxide nanoparticles had a large specific surface area: larger than 350 m2/g. The obtained titanium oxide nanoparticles showed an enhanced adsorption towards the cationic dye molecules. The selective adsorption corresponded to presence of layered titanic acid on the obtained anatase TiO 2 nanoparticles.

  2. Metal-Metal Bonds and Metal Carbon Bonds in the Chemistry of Molybdenum and Tungsten Alkoxides.

    Science.gov (United States)

    1983-02-07

    isopropoxy and neopentoxy compounds are oligomers [MoO 2(OR)21 n of, as yet, unknown struc- 2_no, syt unkow stuc 34 tures. A clean synthesis of the latter...to green solutions containing the triangulo Mo 30(OR)to compounds (see Figure 5). A clean, direct synthesis of these compounds is by the addition of...Also, the W-O distances associated with the W 2( 2-OPri) 2 group are asymetric , averaging 1.92 X and 2.10 X to W(1) and W(2), respectively. The

  3. Influence of chelation ratio of metal alkoxides on aging of PZT 53/47 ...

    Indian Academy of Sciences (India)

    based synthesis routes, generally demands the use of chelating agents in order to avoid fast hydrolysis and also to allow an easier manipulation of intermediates as well as final solutions. Under these conditions, stability issues sometimes can be ...

  4. Towards NHC stabilized alkylgallium alkoxide/aryloxide cations – The advances, the limitations and the challenges

    Czech Academy of Sciences Publication Activity Database

    Dabrowska, A. M.; Hurko, A.; Dranka, M.; Varga, Vojtěch; Urbańczyk, M.; Horegland, P.

    2017-01-01

    Roč. 840, JUL 2017 (2017), s. 63-69 ISSN 0022-328X R&D Projects: GA ČR(CZ) GA14-08531S Institutional support: RVO:61388955 Keywords : carbene * cations * gallium Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.184, year: 2016

  5. Characterization of Titanium Oxide Nanoparticles Obtained by Hydrolysis Reaction of Ethylene Glycol Solution of Alkoxide

    Directory of Open Access Journals (Sweden)

    Naofumi Uekawa

    2012-01-01

    Full Text Available Transparent and stable sols of titanium oxide nanoparticles were obtained by heating a mixture of ethylene glycol solution of titanium tetraisopropoxide (TIP and a NH3 aqueous solution at 368 K for 24 h. The concentration of NH3 aqueous solution affected the structure of the obtained titanium oxide nanoparticles. For NH3 aqueous solution concentrations higher than 0.2 mol/L, a mixture of anatase TiO2 nanoparticles and layered titanic acid nanoparticles was obtained. The obtained sol was very stable without formation of aggregated precipitates and gels. Coordination of ethylene glycol to Ti4+ ions inhibited the rapid hydrolysis reaction and aggregation of the obtained nanoparticles. The obtained titanium oxide nanoparticles had a large specific surface area: larger than 350 m2/g. The obtained titanium oxide nanoparticles showed an enhanced adsorption towards the cationic dye molecules. The selective adsorption corresponded to presence of layered titanic acid on the obtained anatase TiO2 nanoparticles.

  6. Lithium-promoted hydrogenation of carbon dioxide to formates by heterobimetallic hydridozinc alkoxide clusters.

    Science.gov (United States)

    Merz, Klaus; Moreno, Mariluna; Löffler, Elke; Khodeir, Lamy; Rittermeier, Andre; Fink, Karin; Kotsis, Konstantinos; Muhler, Martin; Driess, Matthias

    2008-01-07

    The remarkably distinct reactivity of hydridozinc heterobimetallic cubanes [(HZnOtBu)4-n(thf LiOtBu)n] 1a-1d towards CO2 is reported--the hydride transfer from Zn-H to CO2 is drastically accelerated in the presence of Li ions in 1b-1d which led to the respective metal formate hydrates; the systems are inspiring models for the selective conversion of water gas into formates on lithium-promoted ZnO supports.

  7. Influence of chelation ratio of metal alkoxides on aging of PZT 53/47 ...

    Indian Academy of Sciences (India)

    Administrator

    Time evolution of mean particle size for the most prominent distribution peak of every R-chelated sample under study is depicted in figure 4, where arrows indicate the 'unimodal age' on each case. As a general tendency, precursor particles are well below the 10 nm range, which is an interesting feature with an immediate ...

  8. Hydrolytic activity of μ-alkoxide/acetato-bridged binuclear Cu(II ...

    Indian Academy of Sciences (India)

    Design and synthesis of artificial hydrolases towards esterolysis received considerable attention due to its ... the decrease in reaction activation energy besides cre- ating a high effective concentration resulting in high .... of a given concentration was almost completely hydro- lysed at 3 min intervals. The obtained half-lives ...

  9. 50 years of superbases made from organolithium compounds and heavier alkali metal alkoxides

    Czech Academy of Sciences Publication Activity Database

    Lochmann, Lubomír; Janata, Miroslav

    2014-01-01

    Roč. 12, č. 5 (2014), s. 537-548 ISSN 1895-1066 R&D Projects: GA ČR GAP106/12/0844 Institutional support: RVO:61389013 Keywords : superbases * heavier alkali metal compounds * lithium-heavier alkali metal interchange Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.329, year: 2013

  10. Mechanistic studies aimed at the development of single site metal alkoxide catalysts for the production of polyoxygenates from renewable resources.

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, Malcolm H. [The Ohio State Univ., Columbus, OH (United States)

    2015-12-15

    The work proposed herein follows on directly from the existing 3 year grant and the request for funding is for 12 months to allow completion of this work and graduation of current students supported by DOE. The three primary projects are as follows. 1.) A comparative study of the reactivity of LMg(OR) (solvent), where L= a β-diiminate or pyrromethene ligand, in the ring-opening of cyclic esters. 2.) The homopolymerization of expoxides, particularly propylene oxide and styrene oxide, and their copolymerizations with carbon dioxide or organic anhydrides to yield polycarbonates or polyesters, respectively. 3.) The development of well-defined bismuth (III) complexes for ring-opening polymerizations that are tolerant of both air and water. In each of these topics special emphasis is placed on developing a detailed mechanistic understanding of the ring-opening event and how this is modified by the employment of specific metal and ligand combinations. This document also provides a report on findings of the past grant period that are not yet in the public domain/published and shows how the proposed work will bring the original project to conclusion.

  11. Electrical properties of (1 0 0)-predominant BaTiO3 films derived from alkoxide solutions of two concentrations

    International Nuclear Information System (INIS)

    Guo Yiping; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi; Kato, Kazumi

    2006-01-01

    Lead-free piezoelectric films with thickness larger than 1 μm integrated on silicon substrates have been receiving considerable attention because of environmental concerns and their potential applications in microelectromechanical systems. We demonstrate that, by chemical solution deposition, it is possible to process (1 0 0)-predominant 1 μm BaTiO 3 films on LaNiO 3 /Pt/TiO x /SiO 2 /Si substrates using thinner high-crystallinity columnar BaTiO 3 films as buffer layers. We point out that this kind of buffer layer prepared with a lower concentration solution on the surface of an LaNiO 3 /Pt electrode is effective in enhancing the crystallinity and orientation degree of final BaTiO 3 films prepared with a higher concentration solution. The 1 μm BaTiO 3 films show good dielectric and insulating characteristics against an applied field, and the conduction current shows Schottky emission behavior at modest voltage and space-charge-limited behavior at higher voltage. We also demonstrate that the (1 0 0)-predominant 1 μm BaTiO 3 films have excellent piezoelectric properties: piezoelectric coefficients d 33 higher than 50 pm/V have been determined for the bare films using atomic force microscopy, which are comparable to those of Pb(Zr,Ti)O 3 films. These results indicate that the (1 0 0)-predominant BaTiO 3 films should be promising candidates for microelectromechanical systems applications

  12. Oxidative tandem alkoxide conjugate addition to nitroalkenes/radical 5-exo cyclizations-a versatile synthesis of functionalized 3-nitrotetrahydrofurans

    Czech Academy of Sciences Publication Activity Database

    Jahn, Ullrich; Rudakov, D.; Jones, P. G.

    2012-01-01

    Roč. 68, č. 5 (2012), s. 1521-1539 ISSN 0040-4020 Institutional research plan: CEZ:AV0Z40550506 Keywords : electron transfer * tandem reaction * tetrahydrofurans * oxidation * radicals Subject RIV: CC - Organic Chemistry Impact factor: 2.803, year: 2012

  13. Gaseous anion chemistry. Hydrogen-deuterium exchange in mono- and dialcohol alkoxide ions: ionization reactions in dialcohols

    International Nuclear Information System (INIS)

    Lloyd, J.R.; Agosta, W.C.; Field, F.H.

    1980-01-01

    The subject of this work is H-D exchange in certain gaseous anions using D 2 as the exchanging agent. The anions involved are produced from ethylene glycol, 1,3-propanediol, 1,4-butanediol, ethanol, 1-propanol, and 1-butanol. Spectra and postulated ionization reactions for these mono- and dialcohols are given. Hydrogen-deuterium exchange occurs in the (M - 1) - and (2M - 1) - ions of ethylene glycol, 1,3-propanediol, and 1,4-butanediol. The amount of exchange occurring is 3-8 times greater in (2M - 1) - than in (M - 1) - . The amount of H-D exchange occurring in ethanol, 1-propanol, and 1-butanol is small or zero in the (2M - 1) - ions and in the (M - 1) - ion for 1-butanol [the only (M - 1) - ion which could be examined experimentally]. The amount of exchange occurring in the (2M - 1) - and (M - 1) - ions from ethylene glycol is not affected by the total pressure or composition of the reaction mixture in the ionization chamber of the mass spectrometer. A novel hydrogen-bridging mechanism is suggested to account for the observed exchange occurring in the dialcohols

  14. Silicification of wood adopted for barrel production using pure silicon alkoxides in gas phase to avoid microbial colonisation.

    Science.gov (United States)

    Guzzon, Raffaele; Widmann, Giacomo; Bertoldi, Daniela; Nardin, Tiziana; Callone, Emanuela; Nicolini, Giorgio; Larcher, Roberto

    2015-02-01

    The paper presents a new approach, covering wood with silica-based material in order to protect it from spoilage due to microbial colonisation and avoiding the loss of the natural features of the wood. Wood specimens derived from wine barrels were treated with methyltriethoxysilane in gas phase, leading to the deposition of a silica nanofilm on the surface. (29)Si and (13)C solid state Nuclear Magnetic Resonance and Scanning Electron Microscope-Energy Dispersive X-ray analysis observations showed the formation of a silica polymeric film on the wood samples, directly bonding with the wood constituents. Inductively Coupled Plasma-Mass Spectroscopy quantification of Si showed a direct correlation between the treatment time and silica deposition on the surface of the wood. The silica-coated wood counteracted colonisation by the main wine spoilage microorganisms, without altering the migration from wood to wine of 21 simple phenols measured using a HPLC-Electrochemical Coulometric Detection. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. The effect of refluxing on the alkoxide-based sodium potassium niobate sol-gel system: Thermal and spectroscopic studies

    Czech Academy of Sciences Publication Activity Database

    Chowdhury, A.; Bould, Jonathan; Londesborough, Michael Geoffrey Stephen; Milne, S.J.

    2011-01-01

    Roč. 184, č. 2 (2011), s. 317-324 ISSN 0022-4596 Institutional research plan: CEZ:AV0Z40320502 Keywords : sol-gel processes * spectroscopy * thermal properties * X-ray diffraction Subject RIV: CA - Inorganic Chemistry Impact factor: 2.159, year: 2011

  16. Crystal structures of a novel NNN pincer ligand and its dinuclear titanium(IV alkoxide pincer complex

    Directory of Open Access Journals (Sweden)

    Jakub Pedziwiatr

    2017-02-01

    Full Text Available This report describes a synthetic protocols and the crystal structures involving a novel pincer-type H3[NNN] ligand, namely di-μ-bromido-μ-{2-(2,2-dimethylpropanimidoyl-N-[2-(2,2-dimethylpropanimidoyl-4-methylphenyl]-4-methylaniline}-bis[(diethyl etherlithium], [Li2Br2(C24H33N3(C4H10O2] (1 and a dinuclear metal complex, namely di-μ-bromido-2:3κ4Br:Br-bis{2-(2,2-dimethylpropanimidoyl-N-[2-(2,2-dimethylpropanimidoyl-4-methylphenyl]-4-methylaniline}-1κ3N,N′,N′′;4κ3N,N′,N′′-tetra-μ-isopropanolato-1:2κ4O:O;3:4κ4O:O-diisopropanolato-1κO,4κO-2,3-dilithium-1,4-dititanium, [Li2Ti2Br2(C24H32N32(C3H7O6] or {[NHNNH]Ti(OiPr3(LiBr2}2 (2. Complex 1, which sits on a twofold rotation axis, is a rare example of a pincer-type ligand which bears ketimine side arms. A unique feature of complex 1 is that the ketimine N atoms have an LiBr(Et2O fragment bonded to them, with the Li atom adopting a distorted tetrahedral geometry. This particular fragment creates an LiBr bridge between the two ketimine sidearms, which leads to a cage-type appearance of the ligand. Complex 2 consists of the previously described ligand and a TiIV metal atom in an octahedral environment, and is located on an inversion center. Complex 2 crystallizes as a dinuclear species with the metal atoms being bridged by an LiBr entity [the Br atoms are disordered and refined in two positions with their site occupation factors refining to 0.674 (12/0.372 (12], and the Li cation being bonded to the isopropoxide O atoms (Li having a tetrahedral coordination as in 1. The organic ligand of compound 2 exhibits disorder in its periphery groups; isopropyl and tert-butyl groups (occupation factors fixed at 0.6/0.4. The novel [NNN]H3 pincer-type ligand was characterized by multinuclear and multidimensional NMR, HRMS and X-ray crystallography. The dinuclear metal complex 2 was characterized by X-ray crystallography. Although each structure exhibits donor N—H groups, no hydrogen bonding is found in either one, perhaps due to the bulky groups around them. One of the ethyl groups of the ether ligand of 1 is disordered and refined in two parts with site-occupation factors of 0.812 (8 and 0.188 (8. One and a half toluene solvent molecules are also present in the asymmetric unit of 2. The toluene molecules were significantly disordered and could not be modeled properly, thus SQUEEZE [Spek (2015. Acta Cryst. C71, 9–18] was used to remove their contributions to the overall intensity data.

  17. Anionic polymerization of acrylates. XIV. Synthesis of MMA/acrylate block copolymers initiated with ester-enolate/tert-alkoxide complex

    Czech Academy of Sciences Publication Activity Database

    Vlček, Petr; Čadová, Eva; Kříž, Jaroslav; Látalová, Petra; Janata, Miroslav; Toman, Luděk; Masař, Bohumil

    2005-01-01

    Roč. 46, č. 14 (2005), s. 4991-5000 ISSN 0032-3861 Institutional research plan: CEZ:AV0Z4050913 Keywords : ligated anionic polymerization * (meth)acrylates * block copolymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.849, year: 2005

  18. Influence of calcination temperature on the photoelectrochemical and photocatalytic properties of porous TiO2 films electrodeposited from Ti(IV)-alkoxide solution

    Czech Academy of Sciences Publication Activity Database

    Wessels, K.; Minnermann, M.; Rathouský, Jiří; Wark, M.; Oekermann, T.

    2008-01-01

    Roč. 112, č. 39 (2008), s. 15122-15128 ISSN 1932-7447 Institutional research plan: CEZ:AV0Z40400503 Keywords : sensitized solar cells * hybrid thin films * zinc oxide films Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.396, year: 2008

  19. Formation of TiO2 domains in Poly (9-vinylcarbazole) thin film by hydrolysis-condensation of a metal alkoxide

    International Nuclear Information System (INIS)

    Barlier, V.; Bounor-Legare, V.; Alcouffe, P.; Boiteux, G.; Davenas, J.

    2007-01-01

    New organic-inorganic hybrid thin films based on Poly (9-vinylcarbazole) (P9VK) and Dioxide titanium (TiO 2 ) bulk-heterojunction were obtained by a hydrolysis-condensation (H-C) process of titanium (IV) isopropoxide in thin film. The TiO 2 distribution in the film was investigated by scanning electron microscopy. The results indicated that homogeneous TiO 2 particles around 100 nm were formed on the surface of the polymer thin film. Photoluminescence spectroscopy has been used to study the charge transfer efficiency in the photoactive layer and results were compared with a simplest elaboration route, the dispersion of TiO 2 anatase in a P9VK solution before spin coating. Results showed that TiO 2 elaborated by H-C exhibits a competitive quenching effect with TiO 2 anatase

  20. Formation of TiO{sub 2} domains in Poly (9-vinylcarbazole) thin film by hydrolysis-condensation of a metal alkoxide

    Energy Technology Data Exchange (ETDEWEB)

    Barlier, V. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Bounor-Legare, V. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Alcouffe, P. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Boiteux, G. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France); Davenas, J. [Laboratoire Materiaux polymeres et Biomateriaux, ingenierie des Materiaux Polymeres, Universite Claude Bernard Lyon 1, 15 bd Latarjet, 69622 Villeurbanne cedex (France)]. E-mail: joel.davenas@univ-lyon1.fr

    2007-06-04

    New organic-inorganic hybrid thin films based on Poly (9-vinylcarbazole) (P9VK) and Dioxide titanium (TiO{sub 2}) bulk-heterojunction were obtained by a hydrolysis-condensation (H-C) process of titanium (IV) isopropoxide in thin film. The TiO{sub 2} distribution in the film was investigated by scanning electron microscopy. The results indicated that homogeneous TiO{sub 2} particles around 100 nm were formed on the surface of the polymer thin film. Photoluminescence spectroscopy has been used to study the charge transfer efficiency in the photoactive layer and results were compared with a simplest elaboration route, the dispersion of TiO{sub 2} anatase in a P9VK solution before spin coating. Results showed that TiO{sub 2} elaborated by H-C exhibits a competitive quenching effect with TiO{sub 2} anatase.

  1. Transformation of barium-titanium chloro-alkoxide compound to BaTiO3 nanoparticles by BaCl2 elimination.

    Science.gov (United States)

    Kosińska-Klähn, Magdalena; John, Łukasz; Drąg-Jarząbek, Anna; Utko, Józef; Petrus, Rafał; Jerzykiewicz, Lucjan B; Sobota, Piotr

    2014-02-03

    In this Article, we present how the molecular precursor of binary oxide material having an excess of alkali earth metal can be transformed to the highly phase pure BaTiO3 perovskite. Here, we synthesized and compared two barium-titanium complexes with and without chloride ligands to determine the influences of different ligands on the phase purity of binary oxide nanoparticles. We prepared two barium-titanium complexes, i.e., [Ba4Ti2(μ6-O)(OCH2CH2OCH3)10(HOCH2CH2OCH3)2(HOOCCPh3)4] (1) and [Ba4Ti2(μ6-O)(μ3,η2-OCH2CH2OCH3)8(μ-OCH2CH2OCH3)2(μ-HOCH2CH2OCH3)4Cl4] (2). The barium-titanium precursors were characterized using elemental analysis, infrared and nuclear magnetic resonance spectroscopies, and single-crystal X-ray structural analysis, and their thermal decomposition products were compared. The complex 1 decomposed at 800 °C to give a mixture of BaTiO3 and Ba2TiO4, whereas 2 gave a BaCl2/BaTiO3 mixture. Particles of submicrometer size (30-50 nm) were obtained after leaching of BaCl2 from the raw powder using deionized water. Preliminary studies of barium titanate doped with Eu(3+) sintered at 900 °C showed that the dominant luminescence band arose from the strong electric dipole transition, (5)D0-(7)F2.

  2. Anionic polymerization of acrylates. Synthesis of (meth)acrylate di- and triblock copolymers using the Li ester-enolate/tert-alkoxide initiating system

    Czech Academy of Sciences Publication Activity Database

    Vlček, Petr; Otoupalová, Jaroslava; Janata, Miroslav; Látalová, Petra; Kurková, Dana; Toman, Luděk; Masař, Bohumil

    2004-01-01

    Roč. 37, č. 2 (2004), s. 344-351 ISSN 0024-9297 R&D Projects: GA ČR GA203/01/0513; GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : ligated anionic polymerization * block copolymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.898, year: 2004

  3. The role of ether-functionalized ionic liquids in the sol–gel process: effects on the initial alkoxide hydrolysis steps

    Czech Academy of Sciences Publication Activity Database

    Donato, Ricardo Keitel; Lavorgna, M.; Musto, P.; Donato, Katarzyna Zawada; Jäger, Alessandro; Štěpánek, Petr; Schrekker, H. S.; Matějka, Libor

    2015-01-01

    Roč. 447, 1 June (2015), s. 77-84 ISSN 0021-9797 R&D Projects: GA ČR GAP108/12/1459; GA MŠk(CZ) LH14292 Institutional support: RVO:61389013 Keywords : ether-functionalized ionic liquids * sol–gel silica * multiple hydrogen-bonds Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.782, year: 2015

  4. The Synthesis of (.eta.5-cyclopentadienyl)Titanium(IV) Alkoxides by Alcoholysis of the Ti- .pí.-Ligand Bond in Permethyl .eta.3:.eta.4-Allyldiene-(.eta.5-cyclopentadienyl)Titanium(II)

    Czech Academy of Sciences Publication Activity Database

    Mach, Karel; Kubišta, Jiří; Trojan, L.; Císařová, I.; Štěpnička, P.

    2003-01-01

    Roč. 6, - (2003), s. 974-977 ISSN 1387-7003 R&D Projects: GA ČR GA203/99/M037 Institutional research plan: CEZ:AV0Z4040901 Keywords : titanium * cyclopentadienyl * ferrocene Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.513, year: 2003

  5. Metal nanoparticle doped coloured coatings on glasses and plastics ...

    Indian Academy of Sciences (India)

    Wintec

    applicable to glass and plastic substrates (Medda et al. 2005a, b; Pal and De 2005; De and De 2006a; Pal and De. 2007a). The manufacturing process involves preparation of sols using suitable metal organic precursors (e.g. alkoxides or functionalized alkoxides also known as in- organic–organic hybrid precursors) and ...

  6. Synthesis of nanocrystalline TiO2 by tartarate gel method

    Indian Academy of Sciences (India)

    Unknown

    ... on the formation of TiO2 nano- crystallites with well-defined crystalline morphology. Nano- crystalline anatase is generally synthesized as hydrothermal methods and sol–gel methods using titanium alkoxides. (Dhage et al 2003). Vapour phase decomposition of tita- nium alkoxide or TiCl4 in an oxygen atmosphere at.

  7. Download this PDF file

    African Journals Online (AJOL)

    A variety of organometallic compounds have been prepared using metal alkoxides as starting materiais (1,2). Also many organo derivatives of titanium (IV) alkoxides are known [3-5). The protonation behaviour, hydrogen bonding and. Lewis acid complexation have been studied. The complexes of the alkyl halides.

  8. Particulate Sol-Gel Synthesis and Characterization of LiMO2 (M=Ni, Ni(0.75)Co(0.25) Using the Thermal and Mass Spectrometry Analyses Work-Station

    National Research Council Canada - National Science Library

    Chang, Chun-Chieh

    2000-01-01

    .... Four different processes: (a)rotary evaporation (b)gelation (c)spray drying and (d)spray decomposition have been developed and studied using inorganic and organometallic precursors other than metal alkoxides...

  9. New Hybrid Route to Biomimetic Synthesis

    National Research Council Canada - National Science Library

    Morse, Daniel

    2003-01-01

    ... for the structure-directing polymerization of titanium dioxide from the appropriate water-stable alkoxide precursor. This result dramatically extends our initial development of the new field we called "Silicon Biotechnology" to an even broader "Functional Inorganic Materials Biotechnology."

  10. Recovery of boric acid from nuclear waste

    International Nuclear Information System (INIS)

    Lahoda, E.J.

    1985-01-01

    Disclosed is a process for separating and recovering boric acid from water containing solids which include boric acid and radionuclides. In the first step, the water is separated from the solids by evaporation of the water at a temperature under 130 0 F In the second step, an alcohol selected from the group consisting of methanol, ethanol, propanol, isopropanol, and mixtures thereof is added to the remaining solids in the amount of at least 1.4 times that stoichiometrically required to react with the boric acid to form boron alkoxide and water to about 100 mole % in excess of stoichiometric. In the third step, the boron alkoxide is separated from the remaining solids by evaporation of the boron alkoxide. In the fourth step, water is added to the volatilized boron alkoxide to form boric acid and an alcohol. And finally, the alcohol is separated from the boric acid by evaporating the alcohol

  11. Sol-gel Process in Preparation of Organic-inorganic Hybrid Materials

    Directory of Open Access Journals (Sweden)

    Macan, J

    2008-07-01

    Full Text Available Organic-inorganic hybrid materials are a sort of nanostructured material in which the organic and inorganic phases are mixed at molecular level. The inorganic phase in hybrid materials is formed by the sol-gel process, which consists of reactions of hydrolysis and condensation of metal (usually silicon alkoxides. Flexibility of sol-gel process enables creation of hybrid materials with varying organic and inorganic phases in different ratios, and consequently fine-tuning of their properties. In order to obtain true hybrid materials, contact between the phases should be at molecular level, so phase separation between thermodynamically incompatible organic and inorganic phases has to be prevented. Phase interaction can be improved by formation of hydrogen or covalent bonds between them during preparation of hybrid materials. Covalent bond can be introduced by organically modified silicon alkoxides containing a reactive organic group (substituent capable of reacting with the organic phase. In order to obtain hybrid materials with desired structures, a detailed knowledge of hydrolysis and condensation mechanism is necessary. The choice of catalyst, whether acid or base, has the most significant influence on the structure of the inorganic phase. Other important parameters are alkoxide concentration, water: alkoxide ratio, type of alkoxide groups, solvent used, temperature, purity of chemicals used, etc. Hydrolysis and condensation of organically modified silicon alkoxides are additionally influenced by nature and size of the organic supstituent.

  12. REACTIVITY OF TERVALENT TITANIUM COMPOUNDS (ETA-5-C5ME5)2TIR (R = ME, ET) - INSERTION VERSUS BETA-HYDROGEN TRANSFER AND OLEFIN EXTRUSION - PREPARATION OF THE PARAMAGNETIC TITANIUM ALKOXIDE, IMINOACYL, ACYL, VINYL, AND AZOMETHIDE COMPLEXES (ETA-5-C5ME5)2TIX AND OXIDATION OF THESE WITH PBCL2 TO THE DIAMAGNETIC TETRAVALENT DERIVATIVES (ETA-5-C5ME5)2TI(X)CL

    NARCIS (Netherlands)

    LUINSTRA, GA; TEUBEN, JH

    The paramagnetic, tervalent titanium alkyls Cp*2TiR (1, R = Me; 2, R = Et) were compared in their behavior toward a range of reactive molecules. These 15-electron, d1 systems appear to be weak Lewis acids, reluctant to form adducts. Only for 1 and Me3CC=N could an instable adduct Cp*2TiR.L be

  13. Final Report: Photo-Directed Molecular Assembly of Multifunctional Inorganic Materials

    Energy Technology Data Exchange (ETDEWEB)

    B.G. Potter, Jr.

    2010-10-15

    This final report details results, conclusions, and opportunities for future effort derived from the study. The work involved combining the molecular engineering of photoactive Ti-alkoxide systems and the optical excitation of hydrolysis and condensation reactions to influence the development of the metal-oxygen-metal network at the onset of material formation. Selective excitation of the heteroleptic alkoxides, coupled with control of alkoxide local chemical environment, enabled network connectivity to be influenced and formed the basis for direct deposition and patterning of Ti-oxide-based materials. The research provided new insights into the intrinsic photoresponse and assembly of these complex, alkoxide molecules. Using a suite of electronic, vibrational, and nuclear spectroscopic probes, coupled with quantum chemical computation, the excitation wavelength and fluence dependence of molecular photoresponse and the nature of subsequent hydrolysis and condensation processes were probed in pyridine-carbinol-based Ti-alkoxides with varied counter ligand groups. Several methods for the patterning of oxide material formation were demonstrated, including the integration of this photoprocessing approach with conventional, dip-coating methodologies.

  14. The performance of Ti-MCM-41 in aqueous media and after mechanical treatment studied by in situ XANES, UV/Vis and test reactions

    DEFF Research Database (Denmark)

    Hagen, Anke; Schueler, K.; Roessner, F.

    2002-01-01

    The influence of water on the epoxidation of cyclohexene with H2O2 and tert-butyl hydroperoxide (tbhp) on Ti-MCM-41 molecular sieves prepared by post-synthetic modification of the support with titanium alkoxides was investigated. The catalytic performance depends on the hydrophilicity/hydrophobic......The influence of water on the epoxidation of cyclohexene with H2O2 and tert-butyl hydroperoxide (tbhp) on Ti-MCM-41 molecular sieves prepared by post-synthetic modification of the support with titanium alkoxides was investigated. The catalytic performance depends on the hydrophilicity...

  15. Thin films of ErNbO.sub.4./sub. and YbNbO.sub.4./sub. prepared by sol–gel

    Czech Academy of Sciences Publication Activity Database

    Jakeš, V.; Rubešová, K.; Hlásek, T.; Polák, V.; Oswald, Jiří; Nádherný, L.

    2016-01-01

    Roč. 78, č. 3 (2016), s. 600-605 ISSN 0928-0707 Institutional support: RVO:68378271 Keywords : rare earth niobate * lithium niobate * doping * metal alkoxide * spin coating Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.575, year: 2016

  16. Catalytic asymmetric Meerwein-Ponndorf-Verley reduction of glyoxylates induced by a chiral N,N'-dioxide/Y(OTf)3complex.

    Science.gov (United States)

    Wu, Wangbin; Zou, Sijia; Lin, Lili; Ji, Jie; Zhang, Yuheng; Ma, Baiwei; Liu, Xiaohua; Feng, Xiaoming

    2017-03-18

    An asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of glyoxylates was for the first time accomplished via an N,N'-dioxide/Y(OTf) 3 complex with aluminium alkoxide and molecular sieves (MSs) as crucial additives. A variety of optically active α-hydroxyesters were obtained with excellent results. A possible reaction mechanism was proposed based on the experiments.

  17. studies on transition metal complexes of herbicidal compounds. ii

    African Journals Online (AJOL)

    a

    donor and it forms binuclear octahedral metal complexes, possessing alkoxide bridging. Cobalt(II) complex exhibits thermochromism. Antimicrobial studies on ..... coordination. N1 or N3 may be involved in this process (Figure 1) [18-20]. (iii) Positive shifts in ν(C-O) and ν(N-H) are strong indications of the participation of the.

  18. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Two -alkoxide/acetate-bridged small molecule binuclear copper(II) complexes were synthesized, and used to promote the hydrolysis of a classic carboxylic acid ester, -nitrophenyl picolinate (PNPP). Both binuclear complexes exhibited good hydrolytic reactivity, giving rise to . 15547- and 17462-fold acceleration over ...

  19. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study · Akshai Kumar Ashoka ... 2012 pp 1343-1352. Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide.

  20. Untitled

    Indian Academy of Sciences (India)

    Oglialoro method of preparation of cis a-phenylcinnamic acids, it was shown that the alkoxide catalysed condensation of phenylacetic ester and aldehydes led to the formation of cis a-phenylcinnamic acids and the corres- ponding ester. It was shown that the products are obtained by the initially formed oxyanion, reacting ...

  1. and heterobimetallic complexes of oxovanadium(V)

    Indian Academy of Sciences (India)

    Unknown

    Recent work in our laboratory has involved the syn- thesis of heterometallic alkoxide coordination com- pounds featuring deprotonated forms of polyhydroxy ligands ..... 9. Perrin D D, Armargo W L F and Perrin D R 1980 Pu- rification of laboratory chemicals 2nd edn (New. York: Pergamon). 10. Funk H and Weiss W 1958 Z.

  2. THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

    Science.gov (United States)

    Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO2 particles via an alkoxide sol-gel method employing a water-immi...

  3. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Multi-walled carbon nanotubes (MWCNTs)/TiO2 composites were synthesized by sol–gel technique using titanium (IV) -butoxide (TNB), titanium (IV) isopropoxide (TIP) and titanium (IV) propoxide (TPP) as different titanium alkoxide precursors. The as-prepared composites were comprehensively characterized by BET ...

  4. Redesign of a Grignard-Based Active Pharmaceutical Ingredient (API) Batch Synthesis to a Flow Process for the Preparation of Melitracen HCl

    DEFF Research Database (Denmark)

    Pedersen, Michael J.; Skovby, Tommy; Mealy, Michael J.

    2018-01-01

    A Grignard-based batch process, for the preparation of Melitracen HCl, has been redesigned to fit a continuous reactor system. The Grignard addition is carried out at room temperature, with subsequent hydrolysis of the magnesium alkoxide intermediate followed by dehydration of the resulting alcoh...

  5. Chemistry of the pyrazolidines. 26. Alkylation of 4-benzyliden-1-phenyl-3,5-dioxopyrazolidines

    International Nuclear Information System (INIS)

    Moldarev, B.L.; Aronzon, M.E.; Adanin, V.M.; Zyakun, A.M.

    1986-01-01

    The reaction of 4-benzyliden-1-phenyl-3,5-dioxopyrazolidines with alkyl halides in the presence of sodium alkoxide gave 1-phenyl-2-alkyl-4-benzyliden- and 1-phenyl-2,4-dialkyl-4-(α-alkoxybenzyl)-3,4-dioxopyrazolines. The structures of these compounds were confirmed by UV, IR, and PMR spectroscopy, and by mass-spectrometry

  6. A new method for the chemoselective reduction of aldehydes and ...

    Indian Academy of Sciences (India)

    hydride source and aluminum alkoxides as catalysts. The reaction is chemoselective, easy to operate, and. ∗. For correspondence readily scalable. These apparent practical advantages make the MPV reduction a particularly attractive green-chemistry approach for reduction of carbonyl compounds.8. MPV reactions are ...

  7. Influence of high temperature processing of sol-gel derived barium titanate thin films deposited on platinum and strontium ruthenate coated silicon wafers

    NARCIS (Netherlands)

    Stawski, Tomasz; Vijselaar, Wouter Jan, Cornelis; Göbel, Ole; Veldhuis, Sjoerd; Smith, B.F.; Blank, David H.A.; ten Elshof, Johan E.

    2012-01-01

    Thin films of barium titanate (BTO) of 200 nm thickness, derived from an alkoxide¿carboxylate sol¿gel process, were deposited on Pt/Ti and SrRuO3/ZrO2¿8%Y2O3 coated Si wafers. Films with a dense columnar microstructure were obtained by repeated deposition of thin amorphous layers from

  8. A coprecipitation technique to prepare ZnNb2O6 powders

    Indian Academy of Sciences (India)

    Unknown

    having narrow particle size distribution (Dhage et al 2003;. Gaikwad et al 2004, 2005). The purpose of this study was to prepare ultrafine ZnNb2O6 powder using coprecipita- tion technique from simple water soluble inorganic salts. This process can avoid complex steps such as refluxing of alkoxides, resulting in less time ...

  9. Role of binder in the synthesis of titania membrane

    Indian Academy of Sciences (India)

    The synthesis of titania membrane through sol–gel route involves hydrolysis of alkoxide, peptization of hydrous oxide of titanium to obtain a sol, adjustment of the sol viscosity by including a binder and filtration of the viscous sol through a microporous support, gelation and sintering to desired temperature. The binder plays ...

  10. Gas-Phase Infrared Photodissociation Spectroscopy of Tetravanadium-oxo and -Oxo-methoxo Cluster-Anions

    Czech Academy of Sciences Publication Activity Database

    Feyel, S.; Schwarz, H.; Schröder, Detlef; Daniel, Ch.; Hartl, H.; Döbler, J.; Sauer, J.; Santambrogio, G.; Wöste, L.; Asmis, K. R.

    2007-01-01

    Roč. 8, č. 11 (2007), s. 1640-1647 ISSN 1439-4235 Institutional research plan: CEZ:AV0Z40550506 Keywords : clusters * density-functional calculation * infrared spectroscopy * vanadium alkoxides * vanadium oxide s Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.502, year: 2007

  11. Fabrication and performances of MWCNT/TiO2 composites derived ...

    Indian Academy of Sciences (India)

    Multi-walled carbon nanotubes (MWCNTs)/TiO2 composites were synthesized by sol–gel technique using titanium (IV) -butoxide (TNB), titanium (IV) isopropoxide (TIP) and titanium (IV) propoxide (TPP) as different titanium alkoxide precursors. The as-prepared composites were comprehensively characterized by BET ...

  12. On the Configurational Stability and Reactivity of Tertiary Silyloxy Carbanions Derived from Stereoselective Brook Rearrangement

    NARCIS (Netherlands)

    Collados, Juan F.; Harutyunyan, Syuzanna R.; Ortiz, Pablo

    Here we report a stereospecific Brook rearrangement/trapping sequence, initiated by the formation of a zinc alkoxide from an enantioenriched (hydroxyallyl)silane. The chiral carbanion resulting from the Brook rearrangement is trapped intermolecularly by carbonyl electrophiles with complete transfer

  13. Dehydration and Dehydrogenation of Alcohols with Mononuclear Cationic Vanadium Oxides in the Gas Phase and Energetics of VOnH0/+ (n = 2, 3)

    Czech Academy of Sciences Publication Activity Database

    Engeser, M.; Schröder, Detlef; Schwarz, H.

    -, č. 17 (2007), s. 2454-2464 ISSN 1434-1948 Grant - others:Deutsche Forschungsgemeinschaft(DE) SFB546 Institutional research plan: CEZ:AV0Z40550506 Keywords : alcohol oxidation * dehydration * mass spectroscopy * metal alkoxides * vanadium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.597, year: 2007

  14. Influence of hydrophobic characteristic of organo-modified precursor ...

    Indian Academy of Sciences (India)

    A shortly revisited point of views from biologists and material scientists have shown what kind of structures and organic functions need to be approached. Until now, there is no organic carbon template to develop networks of waxy polymers, but organosilicon chemistry supplies a series of alkoxides with different organic ...

  15. Hydrogen bonding lowers intrinsic nucleophilicity of solvated nucleophiles.

    Science.gov (United States)

    Chen, Xin; Brauman, John I

    2008-11-12

    The relationship between nucleophilicity and the structure/environment of the nucleophile is of fundamental importance in organic chemistry. In this work, we have measured nucleophilicities of a series of substituted alkoxides in the gas phase. The functional group substitutions affect the nucleophiles through ion-dipole, ion-induced dipole interactions and through hydrogen bonding whenever structurally possible. This set of alkoxides serves as an ideal model system for studying nucleophiles under microsolvation settings. Marcus theory was applied to analyze the results. Using Marcus theory, we separate nucleophilicity into two independent components, an intrinsic nucleophilicity and a thermodynamic driving force determined solely by the overall reaction exothermicity. It is found that the apparent nucleophilicities of the substituted alkoxides are always much lower than those of the unsubstituted ones. However, ion-dipole, ion-induced dipole interactions, by themselves, do not significantly affect the intrinsic nucleophilicity; the decrease in the apparent nucleophilicity results from a weaker thermodynamic driving force. On the other hand, hydrogen bonding not only stabilizes the nucleophile but also increases the intrinsic barrier height by 3 to approximately 4 kcal mol (-1). In this regard, the hydrogen bond is not acting as a perturbation in the sense of an external dipole but more directly affects the electronic structure and reactivity of the nucleophilic alkoxide. This finding offers a deeper insight into the solvation effect on nucleophilicity, such as the remarkably lower reactivities in nucleophilic substitution reactions in protic solvents than in aprotic solvents.

  16. The Production of Nanoparticulate Ceria Using Reverse Micelle Sol-Gel Techniques

    Czech Academy of Sciences Publication Activity Database

    Mason, S.; Holliman, P.; Kalaji, M.; Klusoň, Petr

    2009-01-01

    Roč. 19, č. 21 (2009), s. 3517-3522 ISSN 0959-9428 Institutional research plan: CEZ:AV0Z40720504 Keywords : ceria * reverse micelles * alkoxide Subject RIV: CC - Organic Chemistry Impact factor: 4.795, year: 2009

  17. Probing the Effect of Six-Membered N-Heterocyclic Carbene—6-Mes—on the Synthesis, Structure and Reactivity of Me2MOR(NHC (M = Ga, In Complexes

    Directory of Open Access Journals (Sweden)

    Martyna Cybularczyk-Cecotka

    2018-02-01

    Full Text Available The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes (M = Ga, In complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe(6-Mes (1 and Me2GaOMe(6-Mes complexes, the analogous Me2InOR(6-Mes are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes (2. The use of bulky alkoxide ligand—OCPh2Me or aryloxide ligand—OC6H4OMe allowed for the synthesis of stable Me2M(OCPh2Me(6-Mes (M = Ga (3 and In (4 as well as Me2M(OC6H4OMe(6-Mes (M = Ga (5 and In (6. The structures of 1–6 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP of rac-lactide.

  18. Assessment of covalent bond formation between coupling agents and wood by FTIR spectroscopy and pull strength tests

    DEFF Research Database (Denmark)

    Rasmussen, Jonas Stensgaard; Barsberg, Søren Talbro; Venås, Thomas Mark

    2014-01-01

    In the focus was the question whether metal alkoxide coupling agents – titanium, silane, and zirconium – form covalent bonds to wood and how they improve coating adhesion. In a previous work, a downshift of the lignin infrared (IR) band ∼1600 cm-1 was shown to be consistent with the formation of ...... importance for improved wood coating adhesion....

  19. Microporous niobia-silica membrane with very low CO2 permeability

    NARCIS (Netherlands)

    Boffa, V.; ten Elshof, J.E.; Petukhov, A.V.; Blank, D.H.A.

    2008-01-01

    A sol-gel-derived microporous ceramic membrane with an exceptionally low permeability for CO2 from gaseous streams was developed and characterized. The sols were prepared from a mixture of niobium and silicon alkoxide precursors by acid-catalyzed synthesis. Microporous films were formed by coating

  20. New Fellows and Honorary Fellow

    Indian Academy of Sciences (India)

    (Allahabad), Ph.D. and D.Sc. (London), FNA, FNASc, FFACS, D.Sc. (h.c.). Date of birth: 16 February 1922. Date of death: 11 July 2004. Specialization: Inorganic & Organometallic Chemistry, Metal Alkoxides and Sol-Gel Chemistry Last known address: 4/682, Jawahar Nagar, Jaipur 302 004. YouTube; Twitter; Facebook ...

  1. Catalysis and Multi-Component Reactions

    Science.gov (United States)

    Shibasaki, Masakatsu; Yus, Miguel; Bremner, Stacy; Comer, Eamon; Shore, Gjergji; Morin, Sylvie; Organ, Michael G.; van der Eycken, Erik; Merkul, Eugen; Dorsch, Dieter; Müller, Thomas J. J.; Ryabukhin, Sergey V.; Ostapchuk, Eugeniy N.; Plaskon, Andrey S.; Volochnyuk, Dmitriy M.; Shivanyuk, Alexander N.; Tolmachev, Andrey A.; Sheibani, Hassan; Babaie, Maryam; Behzadi, Soheila; Dabiri, Minoo; Bahramnejad, Mahboobeh; Bashiribod, Sahareh; Hekmatshoar, Rahim; Sadjadi, Sodeh; Khorasani, Mohammad; Polyakov, Anatoliy I.; Eryomina, Vera A.; Medvedeva, Lidiya A.; Tihonova, Nadezhda I.; Listratova, Anna V.; Voskressensky, Leonid G.; Merkul, Eugen; Dorsch, Dieter; Müller, Thomas J. J.; Sheibani, Hassan; Esfandiarpoor, Zeinab; Behzadi, Soheila; Titova, Julia A.; Fedorova, Olga V.; Ovchinnikova, Irina G.; Valova, Marina S.; Koryakova, Olga V.; Rusinov, Gennady L.; Charushin, Valery N.; Hekmatshoar, Rahim; Sadjadi, Sodeh

    We have been studying the development of new asymmetric two-center catalysis using rare earth alkoxides and bifunctional sugar and related ligands. In The Fourth International Conference on Multi-Component Reactions and Related Chemistry (MCR 2009), new catalytic asymmetric reactions using catalysts 1 and 2 and catalytic asymmetric syntheses of ranirestat 3 and tamiflu 4 will be presented.

  2. Y5U multilayer ceramic capacitors with high-specific capacitance and low-equivalent series resistance.

    Science.gov (United States)

    Ochi, A; Mori, T; Nakanishi, M; Utsumi, K; Abe, S; Yoshimoto, T

    1991-01-01

    A dielectric powder material, for Y5U multilayer ceramic capacitors was developed in the Pb(Mg(1/3)Nb(2/3))O (3)-Pb(Ni(1/3)Nb(2/3))O(3)-PbTiO (3) ternary system by using an alkoxide process. Multilayer ceramic chip capacitors (10 muF) with high specific capacitances were fabricated using this powder. A Ag80%-Pd20% alloy was used for the internal electrodes. The alkoxide-derived capacitor had an extremely high specific capacitance of about 500 muF/cm(3) and a small temperature dependence meeting Y5U specifications of the EIA standard. The equivalent series resistance was approximately 20 mOmega at 500 kHz. The breakdown voltages of the capacitor were 300 V or higher. In accelerated load life tests and load humidity tests, no degradation of insulation resistance was found during 1000 h of testing.

  3. Supported Single-Site Ti(IV) on a Metal–Organic Framework for the Hydroboration of Carbonyl Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhiyuan [College; amp, Molecular Sciences, Institute of Advanced Studies, Wuhan University, Wuhan 430072, PR China; Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Liu, Dong [College; amp, Molecular Sciences, Institute of Advanced Studies, Wuhan University, Wuhan 430072, PR China; Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Camacho-Bunquin, Jeffrey [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Zhang, Guanghui [Department; Yang, Dali [College; amp, Molecular Sciences, Institute of Advanced Studies, Wuhan University, Wuhan 430072, PR China; Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; López-Encarnación, Juan M. [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Department; Xu, Yunjie [Department; Ferrandon, Magali S. [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Niklas, Jens [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Poluektov, Oleg G. [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Jellinek, Julius [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Lei, Aiwen [College; amp, Molecular Sciences, Institute of Advanced Studies, Wuhan University, Wuhan 430072, PR China; Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Bunel, Emilio E. [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Delferro, Massimiliano [Chemical; amp, Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States

    2017-10-10

    ABSTRACT: A stable and structurally well-defined titanium alkoxide catalyst supported on a metal-organic-framework (MOF) of UiO-67 topology (ANL1-Ti(OiPr)2) was synthesized and fully characterized by a variety of analytical and spectroscopic techniques, including BET, TGA, PXRD, XAS, DRIFT, SEM, and DFT computations. The Ti-functionalized MOF was demonstrated active for the catalytic hydroboration of a wide range of aldehydes and ketones with HBpin as the boron source. Compared to traditional homogeneous and supported hydroboration catalysts, ANL1-Ti(OiPr)2 is completely recyclable and reusable, making it a promising hydroboration catalyst alternative for green and sustainable chemical synthesis. DFT calculations suggest that the catalytic hydroboration proceeds via a (1) hydride transfer between the active Ti-hydride species and a carbonyl moiety (rate determining step), and (2) alkoxide transfer (intramolecular σ-bond metathesis) to generate the boronate ester product.

  4. Small-angle scattering investigation of silica xerogels and sonogels prepared with ionic liquid pyridinium tetrafluoroborate

    Directory of Open Access Journals (Sweden)

    László Almásy

    2017-09-01

    Full Text Available Silica matrices were prepared via acid catalysed sol-gel processing augmented with sonocatalysis. As silica precursors, a mixture of tetra-functionalized alkoxide (TMOS and three-functionalized alkoxide methyl-trimethoxysilane (MTMS were employed. Ionic liquid N-butyl-3-methylpyridinium tetrafluoroborate ([bmPy][BF4], was used in various proportions, aiming to catalyse the sol-gel reactions, and to influence the mesoporous silica materials properties, serving as pore template. Small-angle neutron (SANS and small-angle X-ray scattering (SAXS techniques were used to explore the xerogels and sonogels microstructure evolution as a function of the IL/Si molar ratio. The results show a strong increase of the primary particle size under the influence of the ionic liquid. Ultrasonic agitation leads to further size increase by ca. 10%.

  5. Precursor type affecting surface properties and catalytic activity of sulfated zirconia

    Directory of Open Access Journals (Sweden)

    Zarubica Aleksandra R.

    2007-01-01

    Full Text Available Zirconium-hydroxide precursor samples are synthesized from Zr-hydroxide, Zr-nitrate, and Zr-alkoxide, by precipitation/impregnation, as well as by a modified sol-gel method. Precursor samples are further sulphated for the intended SO4 2- content of 4 wt.%, and calcined at 500-700oC. Differences in precursors’ origin and calcination temperature induce the incorporation of SO4 2- groups into ZrO2 matrices by various mechanisms. As a result, different amounts of residual sulphates are coupled with other structural, as well as surface properties, resulting in various catalytic activities of sulphated zirconia samples. Catalyst activity and selectivity are a complex synergistic function of tetragonal phase fraction, sulphates contents, textural and surface characteristics. Superior activity of SZ of alkoxide origin can be explained by a beneficial effect of meso-pores owing to a better accommodation of coke deposits.

  6. Sol-gel derived sorbents

    Science.gov (United States)

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  7. Nucleophilic stabilization of water-based reactive ink for titania-based thin film inkjet printing

    DEFF Research Database (Denmark)

    Gadea, Christophe; Marani, Debora; Esposito, Vincenzo

    2017-01-01

    -methyldiethanolamine (MDEA) used as nucleophilic ligand. The function of the ligand is to control the fast hydrolysis/condensation reactions in water for the metal alkoxide before deposition, leading to formation of the TiO2 only after the jet process. The evolution of the titanium-ligand interactions at increasing amount......Drop on demand deposition (DoD) of titanium oxide thin films (water-based solution by a combined use of titanium isopropoxide and n...

  8. Porous hydroxyapatite-TiO2 nanocomposites from natural phosphates and their decolorization properties. Photoactive hydroxyapatite-TiO2 nanopowders

    Science.gov (United States)

    Bouyarmane, H.; Saoiabi, S.; El Hanbali, I.; El Karbane, M.; Rami, A.; Masse, S.; Laghzizil, A.; Coradin, T.

    2015-07-01

    Titanium dioxide-hydroxyapatite nanopowders were prepared by the simultaneous gelation of a titanium alkoxide and precipitation of a redisolved natural phosphate mineral. Evolution of the crystallinity, porous features and surface reactivity of these powders as a function of Ti content and heating was studied. Optimal conditions were found for the preparation of a low-cost nanocomposite powder that was as effective as pure titania for the decolorization of methylene blue solutions.

  9. Semicrystalline Ferroelectric Fluoropolymers and Process for Preparing Same

    Science.gov (United States)

    2000-12-05

    methylcyclopenta-[/]- phenanthrene titanium trichloride ([2-Me-Cp[/lPhen]TiCl3), 1’-1 5808 Xu and Chung Macromokcules, Vol. 33, No. 16, 2000 |Ph,C... aluminum was preferred rather than /?-hydridc elimination. The suppression of ^-hydride elimination was attributed to the unfavorable /3-agostic...alkoxide. A toluene slurry of the powdery solid was then reacted with a 3 molar equivalent of diethylaluminum chloride for 12 h to form the PP- aluminum

  10. ARL Summer Student Research Symposium. Volume 2: Compendium of Abstracts

    Science.gov (United States)

    2012-08-01

    successfully deposited onto an aluminum substrate. The deposited copper coating was analyzed using a scanning electron microscope and a stereoscope...commercially available boron trichloride (BCl3), silicon tetrachloride (SiCl4), and perflouro-t-butanol. Upon lithiation, the perflouro-t-butyl alkoxide can...behavior at each loading rate. Aluminum 6061-T6 and Hadfield’s Austenitic Manganese Steel (AMS) thin sheet specimens were also studied under same

  11. ARL Summer Student Research Symposium. Volume 1: Select Papers

    Science.gov (United States)

    2012-08-01

    available boron trichloride (BCl3), silicon tetrachloride (SiCl4), and perflouro-t-butanol. Upon lithiation, the perflouro-t-butyl alkoxide can...Strain Rates. International Journal of Plasticity 2011, 27, 1–24. 10. Williams, C.; Ramesh, K. T.; Dandekar, D. P. Spall Response of 1100-O Aluminum ...Introduction to Dislocations; Butterworth-Heinemann, Kidlington, Oxford, 2001. 199 14. Thomas, J. F. Third-Order Elastic Constants of Aluminum

  12. Basic organometallic chemistry: containing comprehensive bibliography

    National Research Council Canada - National Science Library

    Haiduc, Ionel; Zuckerman, Jerry J

    1985-01-01

    .... Organometallic chemistry is the discipline dealing with compounds containing at least one direct metal-carbon bond. This bond can be simple covalent [as in lead tetraethyl, Pb(C H )J or π-dative [as in ferrocene, Fe(i/ 5 2 5 -C 5 H 5 ) 2 ] or even predominantly ionic [as in ethylsodium, N a + C 2 Hs ]. On this basis, compounds like metal alkoxides, [for example, alu...

  13. Structural studies of gels and gel-glasses in the SiO2-GeO2 system using vibrational spectroscopy

    Science.gov (United States)

    Mukherjee, Shyama P.; Sharma, Shiv K.

    1986-01-01

    GeO2 gel and gels in the SiO2-GeO2 system synthesized by the hydrolytic polycondensation of metal alkoxides have been studied by infrared and Raman spectroscopic techniques. The molecular structures, hydroxyl contents, and crystallinity of gels and gel-glasses in relation to the thermal history and GeO2 concentration were investigated. The binary compositions having up to 70 mol percent GeO2 were examined.

  14. Iron on mixed zirconia-titania substrate F-T catalyst

    International Nuclear Information System (INIS)

    Dyer, P.N.; Nordquist, A.F.; Pierantozzi, R.

    1988-01-01

    This patent deals with a Fischer-Tropsch catalyst comprising iron co-deposited with or deposited on particles comprising a mixture of zirconia and titania, preferably formed by co-precipitation of compounds convertible to zirconia and titania, such as zirconium and titanium alkoxide. The invention also comprises the method of making this catalyst and an improved Fischer-Tropsch reaction process in which the catalyst is utilized

  15. Ring-opening of cyclic ethers by aluminum hydridotriphenylborate.

    Science.gov (United States)

    Mukherjee, Debabrata; Osseili, Hassan; Truong, Khai-Nghi; Spaniol, Thomas P; Okuda, Jun

    2017-03-25

    Molecular aluminum hydride [(L)AlH 2 ] (L = Me 3 TACD) reacted with 2 equiv. of BPh 3 in THF or THP to give the cationic alkoxides [(L)Al(OR)][HBPh 3 ] (R = nBu, nPent) by facile ring-opening of the cyclic ethers. The C α -O bond cleavage which involves the isolable intermediate [(L)AlH][HBPh 3 ] is a result of hydride transfer to C α from [HBPh 3 ] - .

  16. Iron on mixed zirconia-titania substrate Fischer-Tropsch catalyst and method of making same

    Science.gov (United States)

    Dyer, Paul N.; Nordquist, Andrew F.; Pierantozzi, Ronald

    1986-01-01

    A Fischer-Tropsch catalyst comprising iron co-deposited with or deposited on particles comprising a mixture of zirconia and titania, preferably formed by co-precipitation of compounds convertible to zirconia and titania, such as zirconium and titanium alkoxide. The invention also comprises the method of making this catalyst and an improved Fischer-Tropsch reaction process in which the catalyst is utilized.

  17. Trends in metallo-organic chemistry of scandium, yttrium, and the lanthanides

    International Nuclear Information System (INIS)

    Singh, A.

    1994-01-01

    Several interesting aspects of the metallo-organic chemistry of group 3 and the lanthanides have been highlighted, which include: (a) the chemistry of a few notable organolanthanide compounds, alkoxo and aryloxo derivatives derived from sterically demanding ligands, (b) new trends in the chemistry of lanthanide heterometallic alkoxides, (c) an account of zero valent organometallics of yttrium and the lanthanides, and (d) aspects of agostic interactions in the lanthanide metallo-organic compounds. (author). 49 refs

  18. Activation of ethers and sulfides by organolanthanide hydrides - molecular-structures of (cp-asterisk(2)y)(2)(mu- och(2)ch(2)0)(thf)(2) and (cp-asterisk-ce-2)(2)(mu-o)(thf)(2)

    NARCIS (Netherlands)

    Deelman, B.J; Booij, M.; Meetsma, A.; Teuben, J.H; Kooijman, H.; Spek, A.L.

    Dialkyl ethers, ROR', are cleaved by hydrides (Cp*(2)LnH)(2) (Ln = Y 1a, La 1b, Ce 1c) to form alkoxides Cp*(2)LnOR (2), Cp*(2)LnOR', R'H, and RH. The extent to which either of the C-O bonds of asymmetric substituted dialkyl ethers ROR' is attacked strongly depends on the alkyl substituents but is

  19. Morphology, structure and optical properties of sol-gel ITO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Stoica, T.F.; Teodorescu, V.S.; Blanchin, M.G.; Stoica, T.A.; Gartner, M.; Losurdo, M.; Zaharescu, M

    2003-08-15

    The alkoxidic route and the spinning deposition were used to prepare monolayer sol-gel indium tin oxide (ITO) films. The morphology and crystalline structure were investigated by cross-section transmission electron microscopy (XTEM) and atomic force microscopy (AFM). The ITO sol-gel mono-layer contains three regions of different porosities. The basic crystalline structure is that of the In{sub 2}O{sub 3} lattice. The optical properties have been studied by optical transmission and spectroscopic ellipsometry.

  20. Engineering of a silica encapsulation platform for hydrocarbon degradation using Pseudomonas sp. NCIB 9816-4.

    Science.gov (United States)

    Sakkos, Jonathan K; Kieffer, Daniel P; Mutlu, Baris R; Wackett, Lawrence P; Aksan, Alptekin

    2016-03-01

    Industrial application of encapsulated bacteria for biodegradation of hydrocarbons in water requires mechanically stable materials. A silica gel encapsulation method was optimized for Pseudomonas sp. NCIB 9816-4, a bacterium that degrades more than 100 aromatic hydrocarbons. The design process focused on three aspects: (i) mechanical property enhancement; (ii) gel cytocompatibility; and (iii) reduction of the diffusion barrier in the gel. Mechanical testing indicated that the compressive strength at failure (σf ) and elastic modulus (E) changed linearly with the amount of silicon alkoxide used in the gel composition. Measurement of naphthalene biodegradation by encapsulated cells indicated that the gel maintained cytocompatibility at lower levels of alkoxide. However, significant loss in activity was observed due to methanol formation during hydrolysis at high alkoxide concentrations, as measured by FTIR spectroscopy. The silica gel with the highest amount of alkoxide (without toxicity from methanol) had a biodegradation rate of 285 ± 42 nmol/L-s, σf  = 652 ± 88 kPa, and E = 15.8 ± 2.0 MPa. Biodegradation was sustained for 1 month before it dropped below 20% of the initial rate. In order to improve the diffusion through the gel, polyvinyl alcohol (PVA) was used as a porogen and resulted in a 48 ± 19% enhancement in biodegradation, but it impacted the mechanical properties negatively. This is the first report studying how the silica composition affects biodegradation of naphthalene by Pseudomonas sp. NCIB 9816-4 and establishes a foundation for future studies of aromatic hydrocarbon biodegradation for industrial application. © 2015 Wiley Periodicals, Inc.

  1. Effect of impurities on sintering and conductivity of yttria-stabilized zirconia

    NARCIS (Netherlands)

    Verkerk, M.J.; Winnubst, Aloysius J.A.; Burggraaf, A.J.

    1982-01-01

    The effect of low concentrations of Fe2O3, Al2O3 and Bi2O3 on the sintering behaviour of (ZrO2)0.83 (YO1.5)0.17, made by alkoxide synthesis, has been investigated. The best results are achieved with Bi2O3 as a sinter agent and a relative density of 95% is obtained at 1200 K. The effects of these

  2. Molten carbonate fuel cell cathode with mixed oxide coating

    Science.gov (United States)

    Hilmi, Abdelkader; Yuh, Chao-Yi

    2013-05-07

    A molten carbonate fuel cell cathode having a cathode body and a coating of a mixed oxygen ion conductor materials. The mixed oxygen ion conductor materials are formed from ceria or doped ceria, such as gadolinium doped ceria or yttrium doped ceria. The coating is deposited on the cathode body using a sol-gel process, which utilizes as precursors organometallic compounds, organic and inorganic salts, hydroxides or alkoxides and which uses as the solvent water, organic solvent or a mixture of same.

  3. Hydroxyaromatic compounds of tantalum, tungsten, and the lighter actinides

    International Nuclear Information System (INIS)

    Gfaller, H.

    1980-01-01

    Some hydroxyaromatic compounds of the elements tantalum, tungsten, thorium and uranium were prepared as well as the basic materials for these synthesis processes, i.e. metal halides and metal alkoxides. The hydroxyaromatic compounds were studied by elemental analysis, IR spectroscopy, 1 H-NMR spectroscopy (if soluble in suitable solvents) and, in some cases, by X-ray fine structure analysis. (orig./EF) [de

  4. Titanium Dioxide Nanoparticles: Synthesis, X-Ray Line Analysis and Chemical Composition Study

    OpenAIRE

    Chenari,Hossein Mahmoudi; Seibel,Christoph; Hauschild,Dirk; Reinert,Friedrich; Abdollahian,Hossein

    2016-01-01

    TiO$_{2}$ nanoparticleshave been synthesized by the sol-gel method using titanium alkoxide and isopropanolas a precursor. The structural properties and chemical composition of the TiO$_{2}$ nanoparticles were studied usingX-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy.The X-ray powder diffraction pattern confirms that the particles are mainly composed of the anatase phase with the preferential orientation along [101] direction.The physical parameters suc...

  5. Reakce organolithných sloučenin s alkalickými alkoxidy, 50 let od objevu superbází

    Czech Academy of Sciences Publication Activity Database

    Lochmann, L.; Janata, Miroslav

    2013-01-01

    Roč. 107, č. 10 (2013), s. 777-782 ISSN 0009-2770 R&D Projects: GA ČR GAP106/12/0844 Institutional support: RVO:61389013 Keywords : organic compounds and alkoxides of alkali metals * lithium-heavier alkali metal exchange * superbases Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.196, year: 2013 http://www.chemicke-listy.cz/common/article-vol_107-issue_10-page_777.html

  6. Sol-gel bonding of silicon wafers

    International Nuclear Information System (INIS)

    Barbe, C.J.; Cassidy, D.J.; Triani, G.; Latella, B.A.; Mitchell, D.R.G.; Finnie, K.S.; Bartlett, J.R.; Woolfrey, J.L.; Collins, G.A.

    2005-01-01

    Low temperature bonding of silicon wafers was achieved using sol-gel technology. The initial sol-gel chemistry of the coating solution was found to influence the mechanical properties of the resulting bonds. More precisely, the influence of parameters such as the alkoxide concentration, water-to-alkoxide molar ratio, pH, and solution aging on the final bond morphologies and interfacial fracture energy was studied. The thickness and density of the sol-gel coating were characterised using ellipsometry. The corresponding bonded specimens were investigated using attenuated total reflectance Fourier transformed infrared spectroscopy to monitor their chemical composition, infrared imaging to control bond integrity, and cross-sectional transmission electron microscopy to study their microstructure. Their interfacial fracture energy was measured using microindentation. An optimum water-to-alkoxide molar ratio of 10 and hydrolysis water at pH = 2 were found. Such conditions led to relatively dense films (> 90%), resulting in bonds with a fracture energy of 3.5 J/m 2 , significantly higher than those obtained using classical hydrophilic bonding (typically 1.5-2.5 J/m 2 ). Ageing of the coating solution was found to decrease the bond strength

  7. Synthesis of Titania-Silica Materials by Sol-Gel

    Directory of Open Access Journals (Sweden)

    Rubia F. S. Lenza

    2002-10-01

    Full Text Available In this work TiO2-SiO2 glasses containing as much as 20 mol % of TiO2 were prepared via sol-gel process using titanium and silicon alkoxides, in the presence of chlorine, in the form of titanium tetrachloride or HCl. The gels were heat-treated until 800 °C. X-ray diffraction and Fourier transform infrared spectroscopy were used to understand the structural properties of TiO2-SiO2 oxides calcined at different temperatures and to evaluate the homogeneity of these materials. The degree of the compactness of the silica network is inferred from the frequency of the asymmetric stretching vibrations of Si-O-Si bonds. Formation of Si-O-Ti bridges, as monitored by the intensity of characteristic 945 cm-1 ¾ 960 cm-1 vibration, is particularly prominent if the method of basic two-step prehydrolysis of silicon alkoxide, addition of titanium alkoxide and completion of hydrolysis was used.

  8. Sol-gel preparation of ion-conducting ceramics for use in thin films

    International Nuclear Information System (INIS)

    Steinhauser, M.I.

    1992-12-01

    A metal alkoxide sol-gel solution suitable for depositing a thin film of La 0.6 Sr 0.4 CoO 3 on a porous substrate has been developed; such films should be useful in fuel cell electrode and oxygen separation membrane manufacture. Crack-free films have been deposited on both dense and porous substrates by dip-coating and spin-coating techniques followed by a heat treatment in air. Fourier transform infrared spectroscopy was used to determine the chemical structure of metal alkoxide solution system. X-ray diffraction was used to determine crystalline phases formed at various temperatures, while scanning electron microscopy was used to determine physical characteristics of the films. Surface coatings have been successfully applied to porous substrates through the control of the substrate pore size, deposition parameters, and firing parameters. Conditions have been defined for which films can be deposited, and for which the physical and chemical characteristics of the film can be improved. A theoretical discussion of the chemical reactions taking place before and after hydrolysis in the mixed alkoxide solutions is presented, and the conditions necessary for successful synthesis are defined. Applicability of these films as ionic and electronic conductors is discussed

  9. Azide groups in higher oxidation state manganese cluster chemistry: from structural aesthetics to single-molecule magnets.

    Science.gov (United States)

    Stamatatos, Theocharis C; Christou, George

    2009-04-20

    This Forum Article overviews the recent amalgamation of two long-established areas, manganese/oxo coordination cluster chemistry involving the higher Mn(II)/Mn(IV) oxidation states and transition-metal azide (N(3)(-)) chemistry. The combination of azide and alkoxide- or carboxylate-containing ligands in Mn chemistry has led to a variety of new polynuclear clusters, high-spin molecules, and single-molecule magnets, with metal nuclearities ranging from Mn(4) to Mn(32) and with ground-state spin values as large as S = 83/2. The organic bridging/chelating ligands are discussed separately as follows: (i) pyridyl alkoxides [the anions of 2-(hydroxymethyl)pyridine (hmpH), 2,6-pyridinedimethanol (pdmH(2)), and the gem-diol form of di-2-pyridyl ketone (dpkdH(2))]; (ii) non-pyridyl alkoxides [the anions of 1,1,1-tris(hydroxymethyl)ethane (thmeH(3)), triethanolamine (teaH(3)), and N-methyldiethanolamine (mdaH(2))]; (iii) other alcohols [the anions of 2,6-dihydroxymethyl-4-methylphenol (LH(3)) and Schiff bases]; (iv) pyridyl monoximes/dioximes [the anions of methyl-2-pyridyl ketone oxime (mpkoH), phenyl-2-pyridyl ketone oxime (ppkoH), and 2,6-diacetylpyridine dioxime (dapdoH(2))]; (v) non-pyridyl oximes [the anions of salicylaldoxime (saoH(2)) and its derivatives R-saoH(2)]. The large structural diversity of the resulting complexes stems from the combined ability of the azide and organic ligands to adopt a variety of ligation and bridging modes. The combined work demonstrates the synthetic novelty that arises when azide is used in conjunction with alcohol-based chelates, the aesthetic beauty of the resulting molecules, and the often fascinating magnetic properties that these compounds possess. This continues to emphasize the extensive and remarkable ability of Mn chemistry to satisfy a variety of different tastes.

  10. CNN pincer ruthenium catalysts for hydrogenation and transfer hydrogenation of ketones: experimental and computational studies.

    Science.gov (United States)

    Baratta, Walter; Baldino, Salvatore; Calhorda, Maria José; Costa, Paulo J; Esposito, Gennaro; Herdtweck, Eberhardt; Magnolia, Santo; Mealli, Carlo; Messaoudi, Abdelatif; Mason, Sax A; Veiros, Luis F

    2014-10-13

    Reaction of [RuCl(CNN)(dppb)] (1-Cl) (HCNN=2-aminomethyl-6-(4-methylphenyl)pyridine; dppb=Ph2 P(CH2 )4 PPh2 ) with NaOCH2 CF3 leads to the amine-alkoxide [Ru(CNN)(OCH2 CF3 )(dppb)] (1-OCH2 CF3 ), whose neutron diffraction study reveals a short RuO⋅⋅⋅HN bond length. Treatment of 1-Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)]⋅(EtOH)n (1-OEt⋅n EtOH), which equilibrates with the hydride [RuH(CNN)(dppb)] (1-H) and acetaldehyde. Compound 1-OEt⋅n EtOH reacts reversibly with H2 leading to 1-H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1-OEt⋅n EtOH and 1-H reveal hydrogen bond interactions and exchange processes. The chloride 1-Cl catalyzes the hydrogenation (5 atm of H2 ) of ketones to alcohols (turnover frequency (TOF) up to 6.5×10(4) h(-1) , 40 °C). DFT calculations were performed on the reaction of [RuH(CNN')(dmpb)] (2-H) (HCNN'=2-aminomethyl-6-(phenyl)pyridine; dmpb=Me2 P(CH2 )4 PMe2 ) with acetone and with one molecule of 2-propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru-hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH2 is mediated by the alcohol and leads to the key "amide" intermediate. Regeneration of the hydride complex may occur by reaction with 2-propanol or with H2 ; both pathways have low barriers and are alcohol assisted. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization

    KAUST Repository

    Xia, Wei

    2015-02-05

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. CO2 saves: The deactivation of cobalt(III)-porphyrin and salen catalysts in propylene oxide/carbon dioxide copolymerization is systematically investigated, revealing a proposed mechanism for the catalyst reduction (see scheme).

  12. Towards the development of selective hydrocarbon oxygenation catalysts

    OpenAIRE

    Guisado Barrios, Gregorio

    2010-01-01

    The synthesis of pure tris(6-hydroxymethyl-2-pyridylmethyl)amine (H₃L₁₁) is reported for the first time. New complexes of H₃L₁₁ with copper(II), manganese(II) and iron(III) have been characterised by X-ray crystallography. Linear [Fe₃(L₁₁)₂](ClO₄)₃ reveals the tightest Fe-O-Fe angle (87.6°) and shortest Fe...Fe distance (2.834 Å) presently found for a weakly antiferromagnetically-coupled high spin alkoxide-bridged polyiron(III) system. H₃L₁₁ provides a route to various hydrophobic peral...

  13. Elaboration and characterisation of yttrium oxide and hafnium oxide powders by the sol-gel process

    International Nuclear Information System (INIS)

    Hours, T.

    1988-01-01

    The two classical sol-gel processes, colloidal and polymeric are studied for the preparation of yttrium oxide and hafnium oxide high performance powders. In the colloidal process, controlled and reproducible conditions for the preparation of yttrium oxide and hafnium oxide sols from salts or alkoxides are developed and the hydrothermal synthesis monodisperse hafnium oxide colloids is studied. The polymeric process is studied with hafnium ethyl-hexylate, hydrolysis kinetics for controlled preparation of sols and gels is investigated. Each step of preparation is detailed and powders obtained are characterized [fr

  14. Symposium on Polymeric Materials for Photonic and Optical Applications Held in New York, NY on August 25-30, 1991

    Science.gov (United States)

    1992-09-01

    of a thin film. obtained using amino salicylic acid as complexing reagent In- a transition metal alkoxide. This condition can be met when perfectly...before and after application of dye. The change in colour solution was prepared by dissolving 10% w/w of commercial 1:1 ethy- from yellow to red-orange...X = 470 nin) of the final -ver slip (Fisher, 18 mm x 0.21 mm), which was then spun at 3000 rpm coloured film increases from 0.05 to 0.30 with

  15. Grain growth control and transparency in spark plasma sintered self-doped alumina materials

    International Nuclear Information System (INIS)

    Suarez, M.; Fernandez, A.; Menendez, J.L.; Torrecillas, R.

    2009-01-01

    Doping alumina particles with aluminum alkoxides allows dense spark plasma sintered (SPSed) materials to be obtained that have a refined grain size compared to pure materials, which is critical for their transparency. An optical model considering pore and grain size distributions has been developed to obtain information about porosity in dense materials. This work suggests that the atomic diffusion mechanisms do not depend on the sintering technique. A reduction in the activation energy by a factor of 2 has been found in SPSed materials.

  16. The Role of MgCl 2 as a Lewis Base in ROMgCl-MgCl 2 Electrolytes for Magnesium-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Baofei [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Huang, Jinhua [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; He, Meinan [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Brombosz, Scott M. [Materials Science Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Vaughey, John T. [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Zhang, Lu [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Burrell, Anthony K. [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Zhang, Zhengcheng [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA; Liao, Chen [Joint Center for Energy Storage Research, Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont Illinois 60439 USA

    2016-02-04

    A series of strong Lewis acid-free alkoxide/siloxide-based Mg electrolytes were deliberately developed with remarkable oxidative stability up to 3.5 V (vs. Mg/Mg2+). Despite the perception of ROMgCl (R=alkyl, silyl) as a strong base, ROMgCl acts like Lewis acid, whereas the role of MgCl2 in was unambiguously demonstrated as a Lewis base through the identification of the key intermediate using single crystal X-ray crystallography. This Lewis-acid-free strategy should provide a prototype system for further investigation of Mg-ion batteries.

  17. Liquid phase low temperature method for production of methanol from synthesis gas and catalyst formulations therefor

    Science.gov (United States)

    Mahajan, Devinder

    2005-07-26

    The invention provides a homogenous catalyst for the production of methanol from purified synthesis gas at low temperature and low pressure which includes a transition metal capable of forming transition metal complexes with coordinating ligands and an alkoxide, the catalyst dissolved in a methanol solvent system, provided the transition metal complex is not transition metal carbonyl. The coordinating ligands can be selected from the group consisting of N-donor ligands, P-donor ligands, O-donor ligands, C-donor ligands, halogens and mixtures thereof.

  18. An S(N)Ar approach to sterically hindered ortho-alkoxybenzaldehydes for the synthesis of olefin metathesis catalysts.

    Science.gov (United States)

    Engle, Keary M; Luo, Shao-Xiong; Grubbs, Robert H

    2015-04-17

    A three-step procedure has been developed for preparing ortho-alkoxybenzaldehydes from ortho-fluorobenzaldehydes that tolerates the use of sterically hindered sodium alkoxide nucleophiles. The protocol is modular and operationally convenient. The ortho-alkoxybenzaldehyde products can be converted in one additional step to ortho-alkoxystyrenes by a Wittig reaction. These styrenes are precursors to the chelating benzylidene moiety in a proposed series of novel ruthenium complexes for use in olefin metathesis. Chelation with three representative styrenes has been demonstrated.

  19. Continuous Hydrolysis and Liquid–Liquid Phase Separation of an Active Pharmaceutical Ingredient Intermediate Using a Miniscale Hydrophobic Membrane Separator

    DEFF Research Database (Denmark)

    Cervera Padrell, Albert Emili; Morthensen, Sofie Thage; Lewandowski, Daniel Jacob

    2012-01-01

    Continuous hydrolysis of an active pharmaceutical ingredient intermediate, and subsequent liquid–liquid (L-L) separation of the resulting organic and aqueous phases, have been achieved using a simple PTFE tube reactor connected to a miniscale hydrophobic membrane separator. An alkoxide product...... a PTFE membrane with 28 cm2 of active area. A less challenging separation of water and toluene was achieved at total flow rates as high as 80 mL/min, with potential to achieve even higher flow rates. The operability and flexibility of the membrane separator and a plate coalescer were compared...

  20. The production and application of a regenerable filter system for adsorption of some atmospheric contaminants.

    Science.gov (United States)

    Sayilkan, Hikmet; Arpaç, Ertuğrul

    2004-05-01

    In this work, a new filter, used to prevent atmospherical pollution, has been developed. Spherical amorphous shaped silicates (such as KC-Siliperl AF 125 and Aluminium silicate 596 FA) were coated with different materials which were prepared from the hydrolysis-condensation products of organically modified silanes and metal alkoxides. The adsorption capacities of such silicates for different solvents; ethylacetate, toluene, n-hexane and cyclohexanone were investigated. It was found that KC-Siliperl AF 125 coated with IMEO (a commercial silane) adsorbed all the solvents better than Aluminium silicate 596 FA, and ethylacetate was adsorbed more than the other solvents.

  1. Preparation of functionalized porous nano-?-Al2O3 powders employing colophony extract

    OpenAIRE

    Sifontes, ?ngela B.; Gutierrez, Brenda; M?naco, Andrea; Yanez, Andreina; D?az, Yraida; M?ndez, Franklin J.; Llovera, Ligia; Ca?izales, Edgar; Brito, Joaqu?n L.

    2014-01-01

    This study reports the synthesis of porous nano alumina employing carboxylato-alumoxanes [Al(O) x (OH) y (O2CR) z ] n as precursors for controlling the pore size, pore size distribution and porosity of the alumina, using a new process ecofriendly. The carboxylato-alumoxanes was prepared by the reaction of boehmite with carboxylic acids. The boehmite was obtained by the hydrolysis of aluminum alkoxide in an aqueous solution. The colophony extract is employed as a source of carboxylic acids. Th...

  2. Oxidative 3,3,3-trifluoropropylation of arylaldehydes

    Directory of Open Access Journals (Sweden)

    Akari Ikeda

    2013-11-01

    Full Text Available A reaction between (E-trimethyl(3,3,3-trifluoroprop-1-en-1-ylsilane (1 and arylaldehydes 2 was triggered by fluoride anions to afford aryl 3,3,3-trifluoropropyl ketones 3 in moderate to good yield. A mechanistic study of this reaction indicated that it occurred via an allyl alkoxide (4. A subsequent 1,3-proton shift of the benzylic proton of 4 forms 3. This reaction involves oxidative 3,3,3-trifluoropropylation of an arylaldehyde to afford 4,4,4-trifluoro-1-arylbutan-1-one.

  3. Piezoelectric properties of lead-free CaBi4Ti4O15 thin films

    Science.gov (United States)

    Arai, Fumihito; Motoo, Kohei; Fukuda, Toshio; Kato, Kazumi

    2004-11-01

    CaBi4Ti4O15 (CBTi144) thin films are evaluated for use as lead-free thin-film piezoelectrics in microelectromechanical systems. CBTi144 thin films were prepared on Pt substrates by dip coating a precursor solution of metal alkoxides. We fabricated a piezoelectric bimorph actuator using those films and analyzed the displacement induced by the electric field. Young's modulus was measured by the vibrating-reed technique and the piezoelectric constant d31 was derived by analysis of bending displacement and measurement of displacement-voltage curve. The measurements revealed that the CBTi144 films had a large piezoelectric constant d31 of 32pm /V.

  4. The performance of Ti-MCM-41 in aqueous media and after mechanical treatment studied by in situ XANES, UV/Vis and test reactions

    DEFF Research Database (Denmark)

    Hagen, Anke; Schueler, K.; Roessner, F.

    2002-01-01

    The influence of water on the epoxidation of cyclohexene with H2O2 and tert-butyl hydroperoxide (tbhp) on Ti-MCM-41 molecular sieves prepared by post-synthetic modification of the support with titanium alkoxides was investigated. The catalytic performance depends on the hydrophilicity....../hydrophobicity of the MCM-41 surface, but also on the interactions between titanium centers and oxidants. Using XANES, a higher coordination number and an irreversible transformation of isolated into oxide-like titanium species was observed when the reaction was performed with H2O2 compared to tbhp. The mechanical...

  5. Studies on the Preparation of Magnetic Photocatalysts

    International Nuclear Information System (INIS)

    Watson, S.; Scott, J.; Beydoun, D.; Amal, R.

    2005-01-01

    A crystalline titanium dioxide coating was deposited onto silica insulated magnetite particles to prepare a stable magnetic photocatalyst. The direct deposition of crystalline titanium dioxide was conducted by aging dispersions of insulated magnetite particles in a titanium sol-gel precursor mixture at 60-90 deg. C. The coating process was found to be influenced by pH, alkoxide precursor concentration, aging time and reaction temperature. A mechanism for the formation of the titanium dioxide coating has been proposed. The photocatalytic performance of the prepared particles was found to be related to the preparation conditions

  6. Lewis Base Activation of Silyl Acetals: Iridium-Catalyzed Reductive Horner-Wadsworth-Emmons Olefination.

    Science.gov (United States)

    Dakarapu, Udaya Sree; Bokka, Apparao; Asgari, Parham; Trog, Gabriela; Hua, Yuanda; Nguyen, Hiep H; Rahman, Nawal; Jeon, Junha

    2015-12-04

    A Lewis base promoted deprotonative pronucleophile addition to silyl acetals has been developed and applied to the iridium-catalyzed reductive Horner-Wadsworth-Emmons (HWE) olefination of esters and the chemoselective reduction of the resulting enoates. Lewis base activation of silyl acetals generates putative pentacoordinate silicate acetals, which fragment into aldehydes, silanes, and alkoxides in situ. Subsequent deprotonative metalation of phosphonate esters followed by HWE with aldehydes furnishes enoates. This operationally convenient, mechanistically unique protocol converts the traditionally challenging aryl, alkenyl, and alkynyl esters to homologated enoates at room temperature within a single vessel.

  7. A utilização de materiais obtidos pelo processo de sol-gel na construção de biossensores The utilization of materials obtained by the sol-gel process in biosensors construction

    Directory of Open Access Journals (Sweden)

    Antonio A. S. Alfaya

    2002-09-01

    Full Text Available The use of sol-gel materials to develop new biosensors has received great attention due to its characteristics and versatility of sol-gel process. An overview is presented of the state-of-the-art of electrochemical biosensors employing sol-gel materials. Low-temperature, porous sol-gel ceramics represent a new class for the immobilization of biomolecules. The rational design of sol-gel sensing materials, based on the judicious choice of the starting alkoxide, encapsulated reagents, and preparation conditions, allows tailoring of material properties in a wide range, and offers great potential for the development of electrochemical biosensors.

  8. Synthesis of Nano-Particles in Flames

    DEFF Research Database (Denmark)

    Johannessen, Tue

    The scope of this work is to investigate the synthesis of aluminum oxide particles in flames from the combustion of an aluminum alkoxide precursor.A general introduction to particles formation in the gas phase is presented with emphasis on the mechanisms that control the particle morphology after...... energy expression.Furthermore, the model is validated by comparison with experimental data of the flame synthesis of titania by combustion of TiCl4 previously presented by Pratsinis et al. (1996).The combination of particle dynamics and CFD simulations has proved to be an efficient method...

  9. Comparison of the properties of simulated synroc synthesized by sol-gel and a novel co - precipitation method

    International Nuclear Information System (INIS)

    Potdar, H.S.; Vijayanand, S.; Khaja Mohaideen, K.; Joy, P.A.; Raja Madhavan, R.; Kutty, K.V.G.; Ambashta, R.D.; Wattal, P.K.

    2009-01-01

    Synroc is a multiphase dense titanate based ceramic designed for the incorporation of high-level waste (HLW) from the reprocessing of spent nuclear fuel. Synroc or synthetic rock consists of four main titanate phases - zirconolite (CaZrTi 2 O 7 ), hollandite (BaAlO 2 Ti 6 O 16 ), perovskite (CaTiO 3 ) and rutile (TiO 2 ), with the matrix composition as shown in Table 1. It is known that these phases have the capacity to incorporate most of the elements into their crystal structures which are present in the HLW derived from the reprocessing of spent nuclear fuel from power reactors. Synroc is considered as the most effective and durable means of immobilising various forms of high-level radioactive wastes for disposal. Synroc is also considered as a low-risk, tailored waste form, offering higher waste loading and over all cost savings. Simulated synroc precursor powders are typically produced by advanced wet chemical methods such as alkoxide hydrolysis and sol-gel routes. These routes were developed to produce powders with well defined physical and chemical characteristics such as correct chemical composition, high degree of homogeneity, reactivity and readily densifiable material to 99% of theoretical density during hot isostatic pressing. However, the reported alkoxide hydrolysis and hydroxide routes suffer from several disadvantages such as use of large quantities of organic solvents and their disposal as effluent, difficulty in maintaining exact chemical composition, use of costly alkoxide precursors which are moisture sensitive and require critical processing conditions to control their rate of hydrolysis, etc. In the present work we report a comparative study the characteristics of synroc-C (14% waste loading) powders and sintered pellets synthesized by the known alkoxide hydrolysis method and a simple chemical co-precipitation route developed by us. The advantages of the co-precipitation route are its simplicity, ease of handling and utilization of cheaper raw

  10. Sol-gel silica films embedding NIR- emitting Yb-quinolinolate complexes

    Energy Technology Data Exchange (ETDEWEB)

    Figus, Cristiana, E-mail: cristiana.figus@dsf.unica.it; Quochi, Francesco, E-mail: cristiana.figus@dsf.unica.it; Piana, Giacomo; Saba, Michele; Mura, Andrea; Bongiovanni, Giovanni [Dipartimento di Fisica, University of Cagliari, SS 554 Bivio per Sestu, I-09042, Monserrato-Cagliari (Italy); Artizzu, Flavia [Dipartimento di Fisica, University of Cagliari and Dipartimento di Scienze Chimiche e Geologiche, University of Cagliari, SS 554 Bivio per Sestu, I-09042, Monserrato-Cagliari (Italy); Mercuri, Maria Laura; Serpe, Angela; Deplano, Paola [Dipartimento di Scienze Chimiche e Geologiche, University of Cagliari, SS 554 Bivio per Sestu, I-09042, Monserrato-Cagliari (Italy)

    2014-10-21

    Sol-gel silica thin films embedding an ytterbium quinolinolato complex (YbClQ{sub 4}) have been obtained using different alkoxides. Homogeneous, crack- and defect-free thin films of optical quality have been successfully deposited on glass substrate by dip-coating. The silica thin films have been characterized by time-resolved photoluminescence. The luminescence properties of the YbClQ{sub 4} are preserved in silica films prepared through an optimized sol-gel approach. The excited state lifetime of the lanthanide is comparable to those observed in bulk and longer than the corresponding ones in solution.

  11. Exploration of the catalytic use of alkali metal bases

    OpenAIRE

    Bao, Wei

    2017-01-01

    This PhD thesis project was concerned with the use of alkali metal amide Brønsted bases and alkali metal alkoxide Lewis bases in (asymmetric) catalysis. The first chapter deals with formal allylic C(sp3)–H bond activation of aromatic and functionalized alkenes for subsequent C–C and C–H bond formations. The second chapter is focused on C(sp3)–Si bond activation of fluorinated pro-nucleophiles in view of C–C bond formations. In the first chapter, a screening of various metal amides...

  12. Preparation of glass-forming materials from granulated blast furnace slag

    Science.gov (United States)

    Alonso, M.; Sáinz, E.; Lopez, F. A.

    1996-10-01

    Glass precursor materials, to be used for the vitrification of hazardous wastes, have been prepared from blast furnace slag powder through a sol-gel route. The slag is initially reacted with a mixture of alcohol (ethanol or methanol) and mineral acid (HNO3 or H2SO4) to give a sol principally consisting of Si, Ca, Al, and Mg alkoxides. Gelation is carried out with variable amounts of either ammonia or water. The gelation rate can be made as fast as desired by adding excess hydrolizing agent or else by distilling the excess alcohol out of the alkoxide solution. The resulting gel is first dried at low temperature and ground. The powder thus obtained is then heat treated at several temperatures. The intermediate and final materials are characterized by thermal analysis, infrared (IR) spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and chemical analysis. From the results, the operating conditions yielding a variety of glass precursors differing in their composition are established. The method, in comparison with direct vitrification of slag, presents a number of advantages: (1) the glass precursor obtained devitrifies at higher temperatures; (2) it enables the adjustment, to a certain extent, of the chemical composition of the glass precursor; and (3) it permits recovering marketable materials at different stages of the process.

  13. Synthesis of 1D, 2D, and 3D ZnO Polycrystalline Nanostructures Using the Sol-Gel Method

    Directory of Open Access Journals (Sweden)

    Yung-Kuan Tseng

    2012-01-01

    Full Text Available This study employed various polyol solvents to synthesize zinc oxide polycrystalline nanostructures in the form of fibers (1D, rhombic flakes (2D, and spheres (3D. The synthetic process primarily involved the use of zinc acetate dihydrate in polyol solutions, which were used to derive precursors of zinc alkoxides. Following hydrolysis at 160°C, the zinc alkoxide particles self-assembled into polycrystalline nanostructures with different morphologies. Following calcination at 500°C for 1 h, polycrystalline ZnO with good crystallinity was obtained. FE-SEM explored variations in surface morphology; XRD was used to analyze the crystalline structures and crystallinity of the products, which were confirmed as ZnO wurtzite structures. FE-TEM verified that the ZnO nanostructures were polycrystalline. Furthermore, we employed TGA/DSC to observe the phase transition. According to the results of property analyses, we proposed models of the relevant formation mechanisms. Finally, various ZnO structures were applied in the degradation of methylene blue to compare their photocatalytic efficiency.

  14. Investigation of the two-photon polymerisation of a Zr-based inorganic-organic hybrid material system

    International Nuclear Information System (INIS)

    Bhuian, B.; Winfield, R.J.; O'Brien, S.; Crean, G.M.

    2006-01-01

    Two-photon polymerisation of photo-sensitive materials allows the fabrication of three dimensional micro- and nano-structures for photonic, electronic and micro-system applications. However the usable process window and the applicability of this fabrication technique is significantly determined by the properties of the photo-sensitive material employed. In this study investigation of a custom inorganic-organic hybrid system, cross-linked by a two-photon induced process, is described. The material was produced by sol-gel synthesis using a silicon alkoxide species that also possessed methacrylate functionality. Stabilized zirconium alkoxide precursors were added to the precursor solution in order to reduce drying times and impart enhanced mechanical stability to deposited films. This enabled dry films to be used in the polymerisation process. A structural, optical and mechanical analysis of the optimised sol-gel material is presented. A Ti:sapphire laser with 80 MHz repetition rate, 100 fs pulse duration and 795 nm is used. The influence of both material system and laser processing parameters including: laser power, photo-initiator concentration and zirconium loading, on achievable micro-structure and size is presented

  15. Preparation and characterization of hybrid materials of epoxy resin type bisphenol a with silicon and titanium oxides by sol-gel process

    International Nuclear Information System (INIS)

    Carrillo C, A.; Osuna A, J. G.

    2011-01-01

    Hybrid materials were synthesized from epoxy resins as a result bisphenol type A-silicon oxide and epoxy resin bisphenol type A-titanium oxide were obtained. The synthesis was done by sol-gel process using tetraethyl orthosilicate (Teos) and titanium isopropoxide (I Ti) as inorganic precursors. The molar ratio of bisphenol A to the inorganic precursors was the studied variable. The materials were characterized by thermal analysis, infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The hybrid nature of the materials was demonstrated through thermal analysis and infrared spectroscopy. In both systems, as the amount of alkoxide increased, the bands described above were more defined. This behavior indicates the interactions between the resin and the alkoxides. Hybrids with Teos showed a smoother and homogeneous surface in its entirety, without irregularities. Hybrids with titanium isopropoxide had low roughness. Both Teos and I Ti hybrids showed a decrease on the atomic weight percentage of carbon due to a slight reduction of the organic part on the surface. (Author)

  16. Preparation and characterization of hybrid materials of epoxy resin type bisphenol a with silicon and titanium oxides by sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo C, A.; Osuna A, J. G., E-mail: acc.carrillo@gmail.com [Universidad Autonoma de Coahuila, Facultad de Ciencias Quimicas, Blvd. Venustiano Carranza y Jose Cardenas Valdes, 25000 Saltillo, Coahuila (Mexico)

    2011-07-01

    Hybrid materials were synthesized from epoxy resins as a result bisphenol type A-silicon oxide and epoxy resin bisphenol type A-titanium oxide were obtained. The synthesis was done by sol-gel process using tetraethyl orthosilicate (Teos) and titanium isopropoxide (I Ti) as inorganic precursors. The molar ratio of bisphenol A to the inorganic precursors was the studied variable. The materials were characterized by thermal analysis, infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The hybrid nature of the materials was demonstrated through thermal analysis and infrared spectroscopy. In both systems, as the amount of alkoxide increased, the bands described above were more defined. This behavior indicates the interactions between the resin and the alkoxides. Hybrids with Teos showed a smoother and homogeneous surface in its entirety, without irregularities. Hybrids with titanium isopropoxide had low roughness. Both Teos and I Ti hybrids showed a decrease on the atomic weight percentage of carbon due to a slight reduction of the organic part on the surface. (Author)

  17. Effect of Chelating Agents on the Stability of Nano-TiO2 Sol Particles for Sol-Gel Coating.

    Science.gov (United States)

    Maeng, Wan Young; Yoo, Mi

    2015-11-01

    Agglomeration of sol particles in a titanium alkoxide (tetrabutyl orthotitanate (TBOT), > 97%) solution during the hydrolysis and condensation steps makes the sol solution difficult to use for synthesizing homogeneous sol-gel coating. Here, we have investigated the effect of stabilizing agents (acetic acid and ethyl acetoacetate (EAcAc)) on the agglomeration of Ti alkoxide particles during hydrolysis and condensation in order to determine the optimized conditions for controlling the precipitation of TiO2 particles. The study was conducted at R(AC) ([acetic acid]/[TBOT]) = 0.1-5 and R(EAcAc)([EAcAc]/[TBOT]) = 0.05-0.65. We also studied the effects of a basic catalyst ethanolamine (ETA), water, and HCl on sol stability. The chelating ligands in the precursor sol were analyzed with FT-IR. The coating properties were examined by focused ion beam. The stabilizing agents (acetic acid and EAcAc) significantly influenced the agglomeration and precipitation of TBOT precursor particles during hydrolysis. As R(AC) and R(EAcAc) increased, the agglomeration remarkably decreased. The stability of the sol with acetic acid and EAcAc arises from the coordination of the chelating ligand to TBOT that hinders hydrolysis and condensation. A uniform fine coating (thickness: 30 nm) on stainless steel was obtained by using an optimized sol with R(AC) = 0.5 and R(EAcAc) = 0.65.

  18. Synthesis engineering of iron oxide raspberry-shaped nanostructures.

    Science.gov (United States)

    Gerber, O; Pichon, B P; Ihiawakrim, D; Florea, I; Moldovan, S; Ersen, O; Begin, D; Grenèche, J-M; Lemonnier, S; Barraud, E; Begin-Colin, S

    2017-01-07

    Magnetic porous nanostructures consisting of oriented aggregates of iron oxide nanocrystals display very interesting properties such as a lower oxidation state of magnetite, and enhanced saturation magnetization in comparison with individual nanoparticles of similar sizes and porosity. However, the formation mechanism of these promising nanostructures is not well understood, which hampers the fine tuning of their magnetic properties, for instance by doping them with other elements. Therefore the formation mechanism of porous raspberry shaped nanostructures (RSNs) synthesized by a one-pot polyol solvothermal method has been investigated in detail from the early stages by using a wide panel of characterization techniques, and especially by performing original in situ HR-TEM studies in temperature. A time-resolved study showed the intermediate formation of an amorphous iron alkoxide phase with a plate-like lamellar structure (PLS). Then, the fine investigation of PLS transformation upon heating up to 500 °C confirmed that the synthesis of RSNs involves two iron precursors: the starting one (hydrated iron chlorides) and the in situ formed iron alkoxide precursor which decomposes with time and heating and contributes to the growth step of nanostructures. Such an understanding of the formation mechanism of RSNs is necessary to envision efficient and rational enhancement of their magnetic properties.

  19. Switching on elusive organometallic mechanisms with photoredox catalysis.

    Science.gov (United States)

    Terrett, Jack A; Cuthbertson, James D; Shurtleff, Valerie W; MacMillan, David W C

    2015-08-20

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.

  20. Report of the results of the fiscal 1997 regional consortium R and D project. Regional consortium energy field / Study on a new production process of functional thin films suitable for recycling and its application to colored glasses (first fiscal year); 1997 nendo chiiki consortium kenkyu kaihatsu jigyo. Chiiki consortium energy bun`ya / recycle ni tekishita kinosei usumaku no shinki seizoho to chakushoku glass eno oyo ni kansuru kenkyu kaihatsu (daiichi nendo) seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    The paper described the fiscal 1997 result. Using organic pigment and dye, the basic composition of sol-gel colored coating liquid for glass bottles and sheets was selected to clarify characteristics of gel films. Moreover, chemical modification and optical sensitivity of metallic alkoxide were studied to obtain a trially produced colored glass bottle use coating liquid. As to sheet glass, strength of the gel film is low, which requires further improvement. In relation to optical sensitive gel films, the reaction of various metallic alkoxides and {beta}-diketones was discussed to clarify chemical reactivity with utltaviolet rays. Trial design was also conducted of the coating equipment. The paper examined by literature the present status of recycling systems of colored glass bottles and the technical development in European countries. The problem is a method to wash colored bottles for sterilization. To make colored films durable, it is necessary to form films by organic-inorganic hybrid thin films. Also discussed was a possibility of changing the washing method by administrative guidance. 27 refs., 62 figs., 42 tabs.

  1. [Carbon-carbon bond formation based on alkenylphosphonates].

    Science.gov (United States)

    Nagaoka, Y

    2001-11-01

    We have been engaged in the development of asymmetric conjugate addition reactions of lithium thiolates, organolithiums and organocopper reagents under the control of external chiral ligands and we have also developed an efficient asymmetric Horner-Wadsworth-Emmons (HWE) reaction using an external chiral Ligand. We attempted to synthesize axial chiral allenes by combination of these conjugate addition reaction and HWE reaction. In the course of this study, we found that Michael-aldol reaction of alkenylphosphonates 1 using LDA and aldehydes results in the direct formation of alpha,beta-unsaturated hydroxyphosphonate 4, which was efficiently converted to allene by treatment with KH or KH-18-crown-6. Furthermore, allenes were synthesized by sequential double HWE reaction in one-flask manner starting from methylenebisphosphonate 8. The key to success is a metal exchange of intermediate lithium alkoxide 4-Li to potassium alkoxide 4-K by the addition of t-BuOK. As our continuous study of carbon-carbon bond formation based on alkenylphosphonates, a cyclization reaction of bisalkenylphosphonate 6 was developed. Although the treatment of 6 with organolithium reagents afforded a mixture of addition-cyclization product 9 and deprotonation-cyclization product 10, the treatment of 6 with LDA gave 10 selectively. These cyclization methods were applied to the synthesis of efficient chiral phosphine ligands.

  2. Erratum to "The mechanism and thermodynamics of transesterification of acetate-ester enolates in the gas phase" : [Int. J. Mass Spectrom. Ion Process. 172 (1998) 25

    Science.gov (United States)

    Haas, George W.; Giblin, Daryl E.; Gross, Michael L.

    1998-02-01

    In solution, base-catalyzed hydrolysis and transesterification of esters are initiated by hydroxide- or alkoxide-ion attack at the carbonyl carbon. At low pressures in the gas phase, however, transesterification proceeds by an attack of the enolate anion of an acetate ester on an alcohol. Fourier transform mass spectrometry (FTMS) indicates that the reaction is the second-order process: -CH2-CO2-R+R'-OH-->-CH2-CO2-R'+R-OH and there is little to no detectable production of either alkoxide anion. Labeling studies show that the product and reactant enolate anion esters undergo exchange of hydrogens located [alpha] to the carbonyl carbon with the deuterium of R'--OD. The extent of the H/D exchange increases with reaction time, pointing to a short-lived intermediate. The alcoholysis reaction rate constants increase with increasing acidity of the primary, straight-chained alkyl alcohols, whereas steric effects associated with branched alcohols cause the rate constants to decrease. Equilibrium constants, which were determined directly from measurements at equilibrium and which were calculated from the forward and reverse rate constants, are near unity and show internal consistency. In the absence of steric effects, the larger enolate is always the favored product at equilibrium. The intermediate for the transesterification reaction, which can be generated at a few tenths of a torr in a tandem mass spectrometer, is tetrahedral, but other adducts that are collisionally stabilized under these conditions are principally loosely bound complexes.

  3. The mechanism and thermodynamics of transesterification of acetate-ester enolates in the gas phase

    Science.gov (United States)

    Haas, George W.; Giblin, Daryl E.; Gross, Michael L.

    1998-01-01

    In solution, base-catalyzed hydrolysis and transesterification of esters are initiated by hydroxide- or alkoxide-ion attack at the carbonyl carbon. At low pressures in the gas phase, however, transesterification proceeds by an attack of the enolate anion of an acetate ester on an alcohol. Fourier transform mass spectrometry (FTMS) indicates that the reaction is the second-order process: -CH2-CO2-R + R'-OH --> - CH2-CO2-R' + R-OH and there is little to no detectable production of either alkoxide anion. Labeling studies show that the product and reactant enolate anion esters undergo exchange of hydrogens located [alpha] to the carbonyl carbon with the deuterium of R'-OD. The extent of the H/D exchange increases with reaction time, pointing to a short-lived intermediate. The alcoholysis reaction rate constants increase with increasing acidity of the primary, straight-chained alkyl alcohols, whereas steric effects associated with branched alcohols cause the rate constants to decrease. Equilibrium constants, which were determined directly from measurements at equilibrium and which were calculated from the forward and reverse rate constants, are near unity and show internal consistency. In the absence of steric effects, the larger enolate is always the favored product at equilibrium. The intermediate for the transesterification reaction, which can be generated at a few tenths of a torr in a tandem mass spectrometer, is tetrahedral, but other adducts that are collisionally stabilized under these conditions are principally loosely bound complexes.

  4. SANS contrast-variation for investigating the microstructure of nanoparticles

    International Nuclear Information System (INIS)

    Bartlett, J.R.; Woolfrey, J.L.

    1999-01-01

    Over the past two decades, the demand for ceramics with high purity, homogeneity and well-controlled bulk and interfacial properties has led to a significant interest in sol-gel technology, often using alkoxide precursors. An inherent advantage of the sol-gel process is that it permits the preparation of multicomponent nanoparticles, with mixing of the elements on a molecular, or at least nanometre, scale. During the preparation of such multi-component nanoparticles, it is essential to promote controlled co-hydrolysis of mixed precursor alkoxides, to obtain a homogeneous distribution of the components. However, this is not always possible due to the constraints of chemistry and cost. Thus, techniques capable of investigating homogeneity and nanoscale segregation of components in the bulk, or at interfaces, during the processing of multicomponent nanoparticles are extremely important in modern Materials Science. Small-angle neutron scattering (SANS) is a powerful technique used in Materials Science for probing microstructural features, such as particle and pore size, or compositional variations, of materials, on lengths scale between ∼ 1 nm and 1 μm. The SANS contrast-variation method is particularly useful for investigating nanoscale segregation at interfaces and/or within the particles. In SANS contrast-variation experiments involving nanoparticles dispersed in a continuous aqueous phase, the scattering length of the continuous phase is adjusted by varying the D 2 O/H 2 O volume ratios, to determine the ratio at which the minimum in the scattering intensity is observed. (authors)

  5. Regioselective Reductive Cross-Coupling Reactions of Unsymmetrical Alkynes.

    Science.gov (United States)

    Reichard, Holly A; McLaughlin, Martin; Chen, Ming Z; Micalizio, Glenn C

    2010-01-01

    The present microreview summarizes our progress over the last few years in defining regioselective reductive cross-coupling reactions of unsymmetrical alkynes with terminal- and internal alkynes, aldehydes, and imines. We begin with a brief historical perspective of metal-mediated reductive dimerization reactions of aromatic alkynes and discuss the challenges associated with "crossed" versions of this mode of reactivity. Next, a collection of available methods that allow for regioselective reductive cross-coupling of internal alkynes with terminal and internal alkynes, aldehydes, and imines is summarized. After an examination of the requirements for regioselectivity in these cases, the logic behind our design of alkoxide-directed titanium-mediated reductive cross-coupling reactions is presented. A nomenclature is introduced to delineate the presumed mechanistic origin of regioselection associated with each reaction design, and a presentation of alkoxide-directed regioselective reductive cross-coupling reactions of alkynes follows. Throughout, principal issues related to reactivity and selectivity are discussed to assess scope and limitations of available methods and to describe the broad challenges that exist for defining complex fragment union reactions based on reductive cross-coupling chemistry.

  6. Low temperature fabrication of barium titanate hybrid films and their dielectric properties

    International Nuclear Information System (INIS)

    Kobayashi, Yoshio; Saito, Hirobumi; Kinoshita, Takafumi; Nagao, Daisuke; Konno, Mikio

    2011-01-01

    A method for incorporating BT nano-crystalline into barium titanate (BT) films is proposed for a low temperature fabrication of high dielectric constant films. BT nanoparticles were synthesized by hydrolysis of a BT complex alkoxide in 2-methoxyethanol (ME)/ethanol cosolvent. As the ME volume fraction in the cosolvent (ME fraction) increased from 0 to 100%, the particle and crystal sizes tended to increase from 13.4 to 30.2 nm and from 15.8 to 31.4 nm, respectively, and the particle dispersion in the solution became more improved. The BT particles were mixed with BT complex alkoxide dissolved in an ME/ethanol cosolvent for preparing a precursor solution that was then spin-coated on a Pt substrate and dried at 150 o C. The dielectric constant of the spin-coated BT hybrid film increased with an increase in the volume fraction of the BT particles in the film. The dissipation factor of the hybrid film tended to decrease with an increase in the ME fraction in the precursor solution. The hybrid film fabricated at a BT fraction of 30% and an ME fraction of 25% attained a dielectric constant as high as 94.5 with a surface roughness of 14.0 nm and a dissipation factor of 0.11.

  7. Combined sol–gel and carbothermal synthesis of ZrC–TiC powders for composites

    International Nuclear Information System (INIS)

    Umalas, Madis; Hussainova, Irina; Reedo, Valter; Young, Der-Liang; Cura, Erkin; Hannula, Simo-Pekka; Lõhmus, Rünno; Lõhmus, Ants

    2015-01-01

    The TiC–ZrC binary compound of nanostructured powders was synthesised by combination of sol–gel and carbothermal reduction. The polymeric precursor of the blend was produced by sol–gel process from titanium tetrabutoxide, zirconium tetrabutoxide and benzene-1.4-diol; then carbothermally reduced to the TiC–ZrC blend at 1600 °C in an inert environment. The chemical reactions occurring in the system were monitored by infrared spectrometry. Stable alkoxide solution was obtained by adding acetylacetone to avoid premature gelation of the metal alkoxide mixture. A solid solution of ZrTiC 2 was produced by spark plasma sintering at temperature of 2000 °C. - Highlights: • A polymeric precursor of TiC–ZrC blend was synthesised by sol–gel process. • The polymeric precursor synthesis was studied by infrared spectroscopy. • TiC–ZrC powder blend was carbothermally reduced from polymeric precursor. • TiC–ZrC powder blend was sintered to ZrTiC 2 solid solution by spark plasma sintering. • Sintered ZrTiC 2 have good mechanical properties

  8. 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.

  9. Synthesis, Characterization, and Electronic Structure Studies of Cubic Bi1.5ZnTa1.5O7 for Photocatalytic Applications

    Directory of Open Access Journals (Sweden)

    Ganchimeg Perenlei

    2015-01-01

    Full Text Available Bi1.5ZnTa1.5O7 (BZT has been synthesized using an alkoxide based sol-gel reaction route. The evolution of the phases produced from the alkoxide precursors and their properties have been characterized as function of temperature using a combination of thermogravimetric analysis (TGA coupled with mass spectrometry (MS, infrared emission spectrometry (IES, X-ray diffraction (XRD, ultraviolet and visible (UV-Vis spectroscopy, Raman spectroscopy, and N2 adsorption/desorption isotherms. The lowest sintering temperature (600°C to obtain phase pure BZT powders with high surface area (14.5 m2/g has been determined from the thermal decomposition and phase analyses. The photocatalytic activity of the BZT powders has been tested for the decolorization of organic azo-dye and found to be photoactive under UV irradiation. The electronic band structure of the BZT has been investigated using density functional theory (DFT calculations to determine the band gap energy (3.12 eV and to compare it with experimental band gap (3.02 eV at 800°C from optical absorption measurements. An excellent match is obtained for an assumption of Zn cation substitutions at specifically ordered sites in the BZT structure.

  10. Silica doped with lanthanum sol-gel thin films for corrosion protection

    Energy Technology Data Exchange (ETDEWEB)

    Abuin, M. [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain); Serrano, A. [Glass and Ceramic Institute, CSIC, C. Kelsen 5, 28049 Madrid (Spain); Llopis, J. [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain); Garcia, M.A. [Glass and Ceramic Institute, CSIC, C. Kelsen 5, 28049 Madrid (Spain); IMDEA Nanoscience, Fco. Tomas y Valiente 7, 28049 Madrid (Spain); Carmona, N., E-mail: n.carmona@fis.ucm.es [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain)

    2012-06-01

    We present here anticorrosive silica coatings doped with lanthanum ions for the protection of metallic surfaces as an alternative to chromate (VI)-based conversion coatings. The coatings were synthesized by the sol-gel method starting from silicon alkoxides and two different lanthanum precursors: La (III) acetate hydrate and La (III) isopropoxide. Artificial corrosion tests in acid and alkaline media showed their effectiveness for the corrosion protection of AA2024 aluminum alloy sheets for coating prepared with both precursors. The X-ray absorption Near Edge Structure and X-ray Absorption Fine Structure analysis of the coatings confirmed the key role of lanthanum in the structural properties of the coating determining its anticorrosive properties. - Highlights: Black-Right-Pointing-Pointer Silica sol-gel films doped with lanthanum ions were synthesized. Black-Right-Pointing-Pointer Films from lanthanum-acetate and La-alkoxide were prepared for comparison purposes. Black-Right-Pointing-Pointer La-acetate is an affordable chemical reactive preferred for the industry. Black-Right-Pointing-Pointer Films properties were explored by scanning electron microscopy and X-Ray absorption spectroscopy. Black-Right-Pointing-Pointer An alternative to anticorrosive pre-treatments for metallic surfaces is suggested.

  11. Consequences of acid strength for isomerization and elimination catalysis on solid acids.

    Science.gov (United States)

    Macht, Josef; Carr, Robert T; Iglesia, Enrique

    2009-05-13

    We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic

  12. Ground State and Excited State Tuning in Ferric Dipyrrin Complexes Promoted by Ancillary Ligand Exchange

    Energy Technology Data Exchange (ETDEWEB)

    Kleinlein, Claudia; Zheng, Shao-Liang; Betley, Theodore A.

    2017-04-24

    Three ferric dipyrromethene complexes featuring different ancillary ligands were synthesized by one electron oxidation of ferrous precursors. Four-coordinate iron complexes of the type (ArL)FeX2 [ArL = 1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene] with X = Cl or tBuO were prepared and found to be high-spin (S = 5/2), as determined by superconducting quantum interference device magnetometry, electron paramagnetic resonance, and 57Fe Mössbauer spectroscopy. The ancillary ligand substitution was found to affect both ground state and excited properties of the ferric complexes examined. While each ferric complex displays reversible reduction and oxidation events, each alkoxide for chloride substitution results in a nearly 600 mV cathodic shift of the FeIII/II couple. The oxidation event remains largely unaffected by the ancillary ligand substitution and is likely dipyrrin-centered. While the alkoxide substituted ferric species largely retain the color of their ferrous precursors, characteristic of dipyrrin-based ligand-to-ligand charge transfer (LLCT), the dichloride ferric complex loses the prominent dipyrrin chromophore, taking on a deep green color. Time-dependent density functional theory analyses indicate the weaker-field chloride ligands allow substantial configuration mixing of ligand-to-metal charge transfer into the LLCT bands, giving rise to the color changes observed. Furthermore, the higher degree of covalency between the alkoxide ferric centers is manifest in the observed reactivity. Delocalization of spin density onto the tert-butoxide ligand in (ArL)FeCl(OtBu) is evidenced by hydrogen atom abstraction to yield (ArL)FeCl and HOtBu in the presence of substrates containing weak C–H bonds, whereas the chloride (ArL)FeCl2 analogue does not react under these conditions.

  13. SYNTHESIS OF STYRENE-BUTADIENE STATISTIC COPOLYMERS CONTAINING MAGNESIUM INITIATOR

    Directory of Open Access Journals (Sweden)

    A. V. Firsova

    2015-01-01

    Full Text Available The article discusses the use of organomagnesium initiators in the synthesis of styrene-butadiene random copolymer (SBR obtained solution polymerization and their influence on the properties of rubber. Selected organic magnesium dialkyl initiator is combined with a modifier, which is a mixed alkoxide of an alkali and alkaline earth metals, which allows to control the micr ostructure of the diene polymer and its molecular weight characteristics. Alcohol derivatives selected high-boiling alcohols tetra (hydroxypropyl ethylenediamine (lapromol 294 and tetrahydrofurfuryl alcohol (TGFS. Selection of high-boiling alcohols due to the fact that the destruction of alkoxide with aqueous polymer degassing they do not fall into the return solvent and almost fall into the exact water. The metal components of alkoxides are lithium, sodium, potassium, magnesium and calcium. The resulting solutions are stable when stored modifier t hroughout the year even at -40 °C. The scheme of obtaining the new catalyst systems based organomagnesium and alcoxide of alkali and alkaline earth metals, which yields as functionalized SBR with a statistical and a distribution block of butadiene and styrene was developed. The process of copolymerization with styrene to butadiene organomagnesium initiators as using an organolithium compound (n-butyllithium was carried out, and without it. Found that the addition of n-butyllithium in the reaction mixture leads to a sharp increase in the rate of reaction. The results of studies of the effect of composition of the initiator system on the structure of diene polymers. It was revealed that a mixed initiator system affords a high conversion of monomers (to 90 % in 1 hour 1,2-polybutadiene content increased to 60 %. The process of polymerization of only a mixture of organomagnesium initiators and alcoxide of alkali and alkaline earth metals are not actively proceeds, conversion of the monomers reaches to 90 % in 4 hours, the microstructure

  14. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    Science.gov (United States)

    Morse, D. E.; Weaver, J. C.

    2001-12-01

    Oceanic diatoms, sponges and other organisms synthesize gigatons per year of silica from silicic acid, ultimately obtained from the weathering of rock. This biogenic silica exhibits a remarkable diversity of structures, many of which reveal a precision of nanoarchitectural control that exceeds the capabilities of human engineering. In contrast to the conditions of anthropogenic and industrial manufacture, the biological synthesis of silica occurs under mild physiological conditions of low temperatures and pressures and near-neutral pH. In addition to the differentiation between biological and abiotic processes governing silica formation, the biomolecular mechanisms controlling synthesis of these materials may offer insights for the development of new, environmentally benign routes for synthesis of nanostructurally controlled silicas and high-performance polysiloxane composites. We found that the needle-like silica spicules made by the marine sponge, Tethya aurantia, each contain an occluded axial filament of protein composed predominantly of repeating assemblies of three similar subunits we named "silicateins." To our surprise, analysis of the purified protein subunits and the cloned silicatein DNAs revealed that the silicateins are highly homologous to a family of hydrolytic enzymes. As predicted from this finding, we discovered that the silicatein filaments are more than simple, passive templates; they actively catalyze and spatially direct polycondensation to form silica, (as well as the phenyl- and methyl-silsesquioxane) from the corresponding silicon alkoxides at neutral pH and low temperature. Catalytic activity also is exhibited by the silicatein subunits obtained by disaggregation of the protein filaments and those produced from recombinant DNA templates cloned in bacteria. This catalytic activity accelerates the rate-limiting hydrolysis of the silicon alkoxide precursors. Genetic engineering, used to produce variants of the silicatein molecule with

  15. Carbonyl Activation by Borane Lewis Acid Complexation: Transition States of H2 Splitting at the Activated Carbonyl Carbon Atom in a Lewis Basic Solvent and the Proton-Transfer Dynamics of the Boroalkoxide Intermediate.

    Science.gov (United States)

    Heshmat, Mojgan; Privalov, Timofei

    2017-07-06

    By using transition-state (TS) calculations, we examined how Lewis acid (LA) complexation activates carbonyl compounds in the context of hydrogenation of carbonyl compounds by H 2 in Lewis basic (ethereal) solvents containing borane LAs of the type (C 6 F 5 ) 3 B. According to our calculations, LA complexation does not activate a ketone sufficiently enough for the direct addition of H 2 to the O=C unsaturated bond; but, calculations indicate a possibly facile heterolytic cleavage of H 2 at the activated and thus sufficiently Lewis acidic carbonyl carbon atom with the assistance of the Lewis basic solvent (i.e., 1,4-dioxane or THF). For the solvent-assisted H 2 splitting at the carbonyl carbon atom of (C 6 F 5 ) 3 B adducts with different ketones, a number of TSs are computed and the obtained results are related to insights from experiment. By using the Born-Oppenheimer molecular dynamics with the DFT for electronic structure calculations, the evolution of the (C 6 F 5 ) 3 B-alkoxide ionic intermediate and the proton transfer to the alkoxide oxygen atom were investigated. The results indicate a plausible hydrogenation mechanism with a LA, that is, (C 6 F 5 ) 3 B, as a catalyst, namely, 1) the step of H 2 cleavage that involves a Lewis basic solvent molecule plus the carbonyl carbon atom of thermodynamically stable and experimentally identifiable (C 6 F 5 ) 3 B-ketone adducts in which (C 6 F 5 ) 3 B is the "Lewis acid promoter", 2) the transfer of the solvent-bound proton to the oxygen atom of the (C 6 F 5 ) 3 B-alkoxide intermediate giving the (C 6 F 5 ) 3 B-alcohol adduct, and 3) the S N 2-style displacement of the alcohol by a ketone or a Lewis basic solvent molecule. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synthesis and characterization of erbium-doped SiO2 nanoparticles fabricated by using reverse micelle and sol-gel processing

    International Nuclear Information System (INIS)

    Park, Hoyyul; Bae, Dongsik

    2012-01-01

    Erbium-doped SiO 2 nanoparticles have been synthesized using a reverse micelle technique combined with metal-alkoxide hydrolysis and condensation. The sizes and the morphologies of the erbium-doped SiO 2 nanoparticles could be changed by varying the molar ratio of water to surfactant. The sizes and the morphologies of the erbium-doped SiO 2 nanoparticles were examined by using a transmission electron microscope. The average size of synthesized erbium-doped SiO 2 nanoparticles was approximately 20 - 25 nm and that of the erbium particles was 3 - 5 nm. The effects of the synthesis parameters, such as the molar ratio of water to surfactant, are discussed.

  17. Mix-solvent-thermal method for the synthesis of anatase nanocrystalline titanium dioxide used in dye-sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Lao, Chunfeng; Chuai, Yutao; Su, Li; Liu, Xiao; Huang, Lan; Cheng, Humin; Zou, Dechun [Department of Polymer Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2005-01-31

    Nanocrystalline TiO{sub 2} with almost pure anatase form has been synthesized through the Mix-solvent-thermal method (MST) by using TiCl{sub 4} as the starting material. The mean size of the synthesized TiO{sub 2} is 10nm with narrow distribution. High-performance dye-sensitized solar cell with nanocrystalline TiO{sub 2} electrode formed from MST was achieved. Its Isc and Voc values reached 21.62mA/cm{sup 2} and 727.9mV, respectively, and the photovoltaic conversion efficiency reached 9.13%, i.e. 7.5% higher than those of solar cells with TiO{sub 2} made from the traditional precursor of titanium alkoxides. To our knowledge they are the highest values obtained from the solar cells with nanocrystalline TiO{sub 2} electrode formed from the hydrolysis of TiCl{sub 4}.

  18. Moving from batch towards continuous organic‐chemical pharmaceutical production

    DEFF Research Database (Denmark)

    Cervera Padrell, Albert Emili

    alkylation reaction was achieved using a filter reactor coupled with a side‐entry tubular reactor, using real‐time in‐line near‐infrared (NIR) spectroscopy for monitoring the reaction and ensuring the right product quality. A subsequent hydrolysis of the alkoxide product was performed in continuous mode......Pharmaceutical ingredients have traditionally been produced in batches using multipurpose stirred vessels. Reactions and separations have typically been tailored to fit these units, facing multiple limitations when transferring synthetic routes from the laboratory to industrial scale. Scaling up...... thus resulted in many cases in low reaction yields and separation efficiencies. These limitations were however compensated by a relatively fast process implementation. For the pharmaceutical industry this meant that new drug products could be exclusively marketed for a longer time period, resulting...

  19. Nanocomposite organomineral hybrid materials. Part I

    Directory of Open Access Journals (Sweden)

    KUDRYAVTSEV Pavel Gennadievich

    2016-02-01

    Full Text Available The paper addresses the issues of alkoxide method of sol-gel synthesis and non-hydrolytic method of sol-gel synthesis and colloidal method of sol-gel synthesis. The authors also consider an alternative approach based on the use of soluble silicates as precursors in the sol-gel technology, of nanocomposites. It was shown that nanocomposites can be produced through aerogels. The paper also analyzes the mixing technologies of nanocomposites preparation. It has been demonstrated the possibility to change the types of nano-phase which is used for obtaining nanocomposites in different approaches. Various models of packaging spherical, fibrous and layered nanoparticles, introduced into the structure of the nanocomposite, in the preparation thereof were examined.

  20. Nanocomposite organomineral hybrid materials. Part 3

    Directory of Open Access Journals (Sweden)

    KUDRYAVTSEV Pavel Gennadievich

    2016-06-01

    Full Text Available The paper addresses the issues of alkoxide method of sol-gel synthesis and non-hydrolytic method of sol-gel synthesis and colloidal method of sol-gel synthesis. The authors also consider an alternative approach based on the use of soluble silicates as precursors in the sol-gel technology, of nanocomposites. It was shown that nanocomposites can be produced through aerogels. The paper also analyzes the mixing technologies of nanocomposites preparation. It has been demonstrated the possibility to change the types of nano-phase which is used for obtaining nanocomposites in different approaches. Various models of packaging spherical, fibrous and layered nanoparticles, introduced into the structure of the nanocomposite, in the preparation thereof were examined.

  1. Effect of vanadium on the obtaining of the titanium dioxide by Sol-Gel Method

    International Nuclear Information System (INIS)

    Granado, S.R.; Silva, D.W.; Lopes, S.A.; Cavalheiro, A.A.

    2011-01-01

    The obtaining of transition metal modified titanium dioxide (TiO 2 ) can be a promising path to promote changes in crystal structure of anatase phase in order to displace the band gap toward frequencies near to visible region. The insertion of the heterovalent ions such as vanadium can be shift the titanium coordination number in the anatase matrix, leading to important changes in the photonic characteristics of the material. In Sol-Gel method, the presence of the non alkoxide precursors can affects the stability of the solution and the gelifying process, with consequences on the characteristics of the material. In this work, it was investigated the effect of 5mol% of vanadium by thermal analysis of the dried gel and XRD and adsorption isotherm in the samples obtained at different temperatures. The decomposition steps of the precursor were associated to phase formation in the material, leading to conclusion that the presence of vanadium affects the stability of anatase phase. (author)

  2. Caracterização de filmes finos de Nb2O5 com propriedades eletrocrômicas Caracterization of OF Nb2O5 thin films with electrochromic properties

    Directory of Open Access Journals (Sweden)

    C. O. Avellaneda

    1998-06-01

    Full Text Available The sols for thin electrochromic coatings of Nb2O5 were obtained by synthesis of the niobium butoxide from BuONa and NbCl5. The ~300nm thick films were deposited by dip-coating technique from the alkoxide solution and calcined at 560ºC in O2 atmosphere during 3 hours. The particles size of niobium oxide (V powder (~20mm was obtained from x-ray diffraction using the Scherrer equation. The coatings were characterized by cyclic voltammetry and cronoamperommetry techniques. The spectral variation of the optical transmittance were determined in situ as a function of the cyclical potencial and memory effect. The insertion process of lithium is reversible and change the film color from transparent (T=80% to dark blue (T=20%.

  3. Synthesis of nanostructured LiTi2(PO4)3 powder by a Pechini-type polymerizable complex method

    International Nuclear Information System (INIS)

    Mariappan, C.R.; Galven, C.; Crosnier-Lopez, M.-P.; Le Berre, F.; Bohnke, O.

    2006-01-01

    The nanostructured NASICON-type LiTi 2 (PO 4 ) 3 (LTP) material has been synthesized by Pechini-type polymerizable complex method. The use of water-soluble ammonium citratoperoxotitanate (IV) metal complex instead of alkoxides as precursor allows to prepare monophase material. Thermal analyses have been carried out on the powder precursor to check the weight loss and synthesis temperature. X-ray powder diffraction analysis (XRD) has been performed on the LTP powder obtained after heating the powder precursor over a temperature range from 550 to 1050 deg. C for 2 h. By varying the molar ratio of citric acid to metal ion (CA/Ti) and citric acid to ethylene glycol (CA/EG), the grain size of the LTP powder could be modified. The formation of small and well-crystalline grains, in the order of 50-125 nm in size, has been determined from the XRD patterns and confirmed by transmission electron microscopy

  4. MgCl 2 : The Key Ingredient to Improve Chloride Containing Electrolytes for Rechargeable Magnesium-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Baofei; Huang, Jinhua; Sa, Niya; Brombosz, Scott M.; Vaughey, John T.; Zhang, Lu; Burrell, Anthony K.; Zhang, Zhengcheng; Liao, Chen

    2016-01-01

    The effect of MgCl2 on a series of chloride containing magnesium electrolytes was investigated. In the presence of extra MgCl2, the electrochemical properties of Grignard reagents (RMgCl, R = Ph, Et, iPr) were significantly improved, and the advance of MgCl2 was further demonstrated in Mg-Mo6S8 rechargeable batteries with improved capacities and much smaller over-potentials. MgCl2 was then further proven to be powerful reagent to improve the performance of well-established strong Lewis acid derived magnesium electrolytes including the “all-phenyl” complex (APC) and alkoxide-based magnesium electrolytes. The results suggest that MgCl2 salt is a very important species to benefit all chloride containing electrolytes for rechargeable magnesium-ion batteries.

  5. Solution-derived sodalite made with Si- and Ge-ethoxide precursors for immobilizing electrorefiner salt

    International Nuclear Information System (INIS)

    Riley, Brian J.; Lepry, William C.; Crum, Jarrod V.

    2016-01-01

    Chlorosodalite has the general form of Na 8 (AlSiO 4 ) 6 Cl 2 and this paper describes experiments conducted to synthesize sodalite with a solution-based approach to immobilize a simulated spent electrorefiner salt solution containing a mixture of alkali, alkaline earth, and lanthanide chlorides. The reactants used were the salt solution, NaAlO 2 , and either Si(OC 2 H 5 ) 4 or Ge(OC 2 H 5 ) 4 . Additionally, seven different glass sintering aids (at loadings of 5 mass%) were evaluated as sintering aids for consolidating the as-made powders using a cold-press-and-sinter technique. This process of using alkoxide additives for the Group IV component can be used to produce large quantities of sodalite at near-room temperature as compared to a method where colloidal silica was used as the silica source. However, the small particle sizes inhibited densification during heat treatments.

  6. Homogeneous catalyst formulations for methanol production

    Science.gov (United States)

    Mahajan, Devinder; Sapienza, Richard S.; Slegeir, William A.; O'Hare, Thomas E.

    1990-01-01

    There is disclosed synthesis of CH.sub.3 OH from carbon monoxide and hydrogen using an extremely active homogeneous catalyst for methanol synthesis directly from synthesis gas. The catalyst operates preferably between 100.degree.-150.degree. C. and preferably at 100-150 psia synthesis gas to produce methanol. Use can be made of syngas mixtures which contain considerable quantities of other gases, such as nitrogen, methane or excess hydrogen. The catalyst is composed of two components: (a) a transition metal carbonyl complex and (b) an alkoxide component. In the simplest formulation, component (a) is a complex of nickel tetracarbonyl and component (b) is methoxide (CH.sub.3 O.sup.13 ), both being dissolved in a methanol solvent system. The presence of a co-solvent such as p-dioxane, THF, polyalcohols, ethers, hydrocarbons, and crown ethers accelerates the methanol synthesis reaction.

  7. One-pot synthesis of linear- and three-arm star-tetrablock quarterpolymers via sequential metal-free ring-opening polymerization using a "catalyst switch" strategy

    KAUST Repository

    Zhao, Junpeng

    2014-08-06

    A "catalyst switch" strategy has been used to sequentially polymerize four different heterocyclic monomers. In the first step, epoxides (1,2-butylene oxide and ethylene oxide) were successively polymerized from a monohydroxy or trihydroxy initiator in the presence of a strong phosphazene base promoter (t-BuP4). Then, an excess of diphenyl phosphate (DPP) was introduced, followed by addition and polymerization of a cyclic carbonate (trimethylene carbonate) and a cyclic ester (δ-valerolactone or ε-caprolactone). DPP acted as both neutralizer of the phosphazenium alkoxide (polyether chain end) and activator of the cyclic carbonate/ester. Using this method, linear- and star-tetrablock quarterpolymers were prepared in one pot. This work is emphasizing the strength of the previously developed catalyst switch strategy for the facile metal-free synthesis of complex macromolecular architectures. © 2014 Wiley Periodicals, Inc.

  8. A "catalyst switch" Strategy for the sequential metal-free polymerization of epoxides and cyclic Esters/Carbonate

    KAUST Repository

    Zhao, Junpeng

    2014-06-24

    A "catalyst switch" strategy was used to synthesize well-defined polyether-polyester/polycarbonate block copolymers. Epoxides (ethylene oxide and/or 1,2-butylene oxide) were first polymerized from a monoalcohol in the presence of a strong phosphazene base promoter (t-BuP4). Then an excess of diphenyl phosphate (DPP) was introduced, followed by the addition and polymerization of a cyclic ester (ε-caprolactone or δ-valerolactone) or a cyclic carbonate (trimethylene carbonate), where DPP acted as both the neutralizer of phosphazenium alkoxide (polyether chain end) and the activator of cyclic ester/carbonate. This work has provided a one-pot sequential polymerization method for the metal-free synthesis of block copolymers from monomers which are suited for different types of organic catalysts. © 2014 American Chemical Society.

  9. Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates.

    Science.gov (United States)

    He, Yulian; Fishman, Zachary S; Yang, Ke R; Ortiz, Brandon; Liu, Chaolun; Goldsamt, Julia; Batista, Victor S; Pfefferle, Lisa D

    2018-02-07

    A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with p-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (p-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250-350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and 1 H NMR spectroscopy. The resulting hydrophobicity correlates with H 2 temperature-programmed reduction (H 2 -TPR) stability, which therefore provides a practical gauge of hydrophobicity.

  10. TiO2 Surface Coating of Mn-Zn Dopped Ferrites Study

    DEFF Research Database (Denmark)

    Solný, Tomáš; Ptacek, Petr; Másilko, Jiří

    2016-01-01

    This study deals with TiO2 coating of powder Mn-Zn ferrite in order to recieve photocatalytic layer on the top of these particles, forming core-shell catalyst. Powder catalysts are of great advance over the world due to the high surface area, considering the kinetics proceeds through heterogenous...... phase boundary catalysis. However their withdrawal from cleaning systems often requires energetically and economically demanding processes such as filtration and ultrafiltration. Since the ferrite is magnetic, the advantage of such formed core-shell photocatalyst is easibility of removing from...... photocatalytic decomposition system using external magnetic field. In this study the surface coating is performed, using Ti alkoxides mixtures with nanosized TiO2 particles and C and Au coating to form film layer of TiO2 on the surface of ferrite. XRD, SEM – EDS analyses are employed to study surface coating....

  11. Lithium-Assisted Copolymerization of CO 2 /Cyclohexene Oxide: A Novel and Straightforward Route to Polycarbonates and Related Block Copolymers

    KAUST Repository

    Zhang, Dongyue

    2016-03-23

    A facile route toward alternating polycarbonates by anionic copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO), using lithium halide or alkoxide as initiators and triisobutylaluminum (TiBA) as activator, is reported. α,ω-Heterobifunctional and α,ω-dihydroxypoly(cyclohexene carbonate)s (PCHC) as well as poly(CHC-co-CHO) copolymers with different carbonate composition could also be easily synthesized by adjusting the amount of TiBA or by adding inert lithium salts. The value of this initiating system also resides in the easy access to PSt-b-PCHC (PSt: polystyrene) and PI-b-PCHC (PI: polyisoprene) block copolymers which can be derived by mere one-pot sequential addition of styrene or dienes first and then of CO2 and CHO under the same experimental conditions. © 2016 American Chemical Society.

  12. Chemically Derived Dense Alumina-Zirconia Composites for Improved Mechanical and Wear Erosion Properties

    Science.gov (United States)

    1998-01-01

    As a result of this funded project high purity Zirconia-Toughened Alumina (ZTA) ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and rheological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. This improved materials should have enhanced properties such strength, toughness, and wear resistance for advanced structural applications, for example engine components in high technology aerospace applications.

  13. Encapsulation of viable animal cells for hybrid bioartificial organs by the Biosil method

    Science.gov (United States)

    Carturan, Giovanni; Dellagiacoma, Giovanni; Rossi, M.; Dal Monte, R.; Muraca, M.

    1997-10-01

    Gas phase silicon alkoxides react with the wet surface of mammalian cells, affording a stable and homogeneous layer of amorphous SiO2 modified by Si-CH3 and Si-H bonds. Layer thickness may be controlled by exposure time. The layer does not suppress cell viability or functionality, and may be applied to cells supported on a trapping network or to cell aggregates. H4-II-E-C3 rat hepatoma cells, Hep G2 human cancer cells and human fibroblasts on various supports were encapsulated by the SiO2 layer and studied in terms of glucose utilization and 3H-leucin incorporation into secreted proteins. In the case of pancreatic islets, encapsulation was carried out without supports, so that original islet volume and features were maintained. In vitro results indicate preservation of vitality and function, as tested by insulin production.

  14. 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

  15. Synthesis of 11C-methylated inulin as a radiopharmaceutical for imaging brain edema and pulmonary edema

    International Nuclear Information System (INIS)

    Hara, Toshihiko; Iio, Masaaki; Inagaki, Keizo

    1988-01-01

    11 C-methylated inulin, supposedly useful for imaging of brain edema and pulmonary edema, was prepared using cyclotron produced 11 CO 2 . The synthesis consists of the production of 11 C-methyl iodide and its coupling with inulin alkoxide sodium in dimethylsulfoxide as solvent. 11 C labeled inulin was purified by alcohol precipitation. The radiochemical yield of pure 11 C-inulin was 34% of 11 CO 2 30 min after the end of bombardment. The blood clearance and body distribution of 11 C was observed in rabbits after i.v. injection of 11 C-inulin. The blood clearance curve was composed of a sum of three exponential functions. The gamma camera image showed that the 11 C activity in blood moved quickly to kidneys and urine and a small dose of radioactivity remained persistently in edematous tissues, i.e. the edematous lung tissues produced by oleic acid treatment. (orig.)

  16. Mixed-Metal Oxo Clusters Structurally Derived from Ti6O4(OR)8(OOCR')8.

    Science.gov (United States)

    Artner, Christine; Koyun, Ayse; Czakler, Matthias; Schubert, Ulrich

    2014-10-01

    The mixed-metal oxo clusters FeTi 5 O 4 (O i Pr) 4 (OMc) 10 (OMc = methacrylate), Zn 2 Ti 4 O 4 (O i Pr) 2 (OMc) 10 , Cd 4 Ti 2 O 2 (OAc) 2 (OMc) 10 (HO i Pr) 2 , [Ca 2 Ti 4 O 4 (OAc) 2 (OMc) 10 ] n , and [Sr 2 Ti 4 O 4 (OMc) 12 (HOMc) 2 ] n were obtained from the reaction of titanium alkoxides with the corresponding metal acetates and methacrylic acid. Their structures are derived from Ti clusters with the composition Ti 6 O 4 (OR) 8 (OOCR') 8 . The Ca and Sr derivatives consist of chains of condensed clusters.

  17. Mixed-Metal Oxo Clusters Structurally Derived from Ti6O4(OR)8(OOCR′)8

    Science.gov (United States)

    Artner, Christine; Koyun, Ayse; Czakler, Matthias; Schubert, Ulrich

    2014-01-01

    The mixed-metal oxo clusters FeTi5O4(OiPr)4(OMc)10 (OMc = methacrylate), Zn2Ti4O4(OiPr)2(OMc)10, Cd4Ti2O2(OAc)2(OMc)10(HOiPr)2, [Ca2Ti4O4(OAc)2(OMc)10]n, and [Sr2Ti4O4(OMc)12(HOMc)2]n were obtained from the reaction of titanium alkoxides with the corresponding metal acetates and methacrylic acid. Their structures are derived from Ti clusters with the composition Ti6O4(OR)8(OOCR′)8. The Ca and Sr derivatives consist of chains of condensed clusters. PMID:25814833

  18. Formation of nanocrystalline barium titanate in benzyl alcohol at room temperature.

    Science.gov (United States)

    Veldhuis, Sjoerd A; Vijselaar, Wouter J C; Stawski, Tomasz M; ten Elshof, Johan E

    2014-12-15

    Nanocrystalline barium titanate (8-10 nm crystallite size) was prepared at temperatures of 23-78 °C through reaction of a modified titanium alkoxide precursor in benzyl alcohol with barium hydroxide octahydrate. The room temperature formation of a perovskite phase from solution is associated with the use of benzyl alcohol as solvent medium. The formation mechanism was elucidated by studying the stability and interaction of each precursor with the solvent and with each other using various experimental characterization techniques. Density functional theory (DFT) computational models which agreed well with our experimental data could explain the formation of the solid phase. The stability of the Ti precursor was enhanced by steric hindrance exerted by phenylmethoxy ligands that originated from the benzyl alcohol solvent. Electron microscopy and X-ray diffraction indicated that the crystallite sizes were independent of the reaction temperature. Crystal growth was inhibited by the stabilizing phenylmethoxy groups present on the surface of the crystallites.

  19. Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

    International Nuclear Information System (INIS)

    Suegama, P.H.; Sarmento, V.H.V.; Montemor, M.F.; Benedetti, A.V.; de Melo, H.G.; Aoki, I.V.; Santilli, C.V.

    2010-01-01

    This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film.

  20. Dense xerogel matrices and films for optical memory

    International Nuclear Information System (INIS)

    Chaput, F.; Boilot, J.P.; Devreux, F.; Canva, M.; Georges, P.; Brun, A.

    1992-01-01

    This paper reports that optically clear gels doped with organic molecules are prepared in the zirconia-silica system by hydrolysis of metal alkoxides in a wet atmosphere. After drying, dense xerogels are obtained which exhibit a closed porosity. By using the same route, organic-inorganic hybrid xerogels are also produced as films. The molecule-matrix interactions are evaluated from the absorption recovery times of the S O → S 1 transition for triphenylmethane dyes. Concerning doped xerogels with other organic molecules having polar groups, the application of the strong polarized electric field of an ultrashort optical pulse allows to locally create a birefringence with a memory effect. This type of sample could be used for optical storage and treatment of information

  1. Preparation of functionalized porous nano-γ-Al2O3powders employing colophony extract.

    Science.gov (United States)

    Sifontes, Ángela B; Gutierrez, Brenda; Mónaco, Andrea; Yanez, Andreina; Díaz, Yraida; Méndez, Franklin J; Llovera, Ligia; Cañizales, Edgar; Brito, Joaquín L

    2014-12-01

    This study reports the synthesis of porous nano alumina employing carboxylato-alumoxanes [Al(O) x (OH) y (O 2 CR) z ] n as precursors for controlling the pore size, pore size distribution and porosity of the alumina, using a new process ecofriendly. The carboxylato-alumoxanes was prepared by the reaction of boehmite with carboxylic acids. The boehmite was obtained by the hydrolysis of aluminum alkoxide in an aqueous solution. The colophony extract is employed as a source of carboxylic acids. The materials were characterized, using XRD, TGA, N 2 physical adsorption, SEM, TEM, NMR and FTIR. A mechanism was proposed for the formation of the synthesized structures. TEM measurements confirmed particle size ranged from 5 to 8 nm.

  2. Preparation of functionalized porous nano-γ-Al2O3 powders employing colophony extract

    Directory of Open Access Journals (Sweden)

    Ángela B. Sifontes

    2014-12-01

    Full Text Available This study reports the synthesis of porous nano alumina employing carboxylato-alumoxanes [Al(Ox(OHy(O2CRz]n as precursors for controlling the pore size, pore size distribution and porosity of the alumina, using a new process ecofriendly. The carboxylato-alumoxanes was prepared by the reaction of boehmite with carboxylic acids. The boehmite was obtained by the hydrolysis of aluminum alkoxide in an aqueous solution. The colophony extract is employed as a source of carboxylic acids. The materials were characterized, using XRD, TGA, N2 physical adsorption, SEM, TEM, NMR and FTIR. A mechanism was proposed for the formation of the synthesized structures. TEM measurements confirmed particle size ranged from 5 to 8 nm.

  3. Formation of bimodal porous silica-titania monoliths by sol-gel route

    Energy Technology Data Exchange (ETDEWEB)

    Ruzimuradov, O N, E-mail: ruzimuradov@rambler.ru [Department of General Chemistry, Faculty of Chemistry, National University of Uzbekistan, 15, Vuzgorodok, Tashkent, 100174 (Uzbekistan)

    2011-10-29

    Silica-titania monoliths with micrometer-scale macroporous and nanometer-scale mesoporous structure and high titania contents are prepared by sol-gel process and phase separation. Titanium alkoxide precursor was not effective in the preparation of high titania content composites because of strong decrease in phase separation tendency. Bimodal porous gels with high titania content were obtained by using inorganic salt precursors such as titanium sulfate and titanium chloride. Various characterization techniques, including SEM, XRD, Hg porosimetry and N{sub 2} adsorption have been carried out to investigate the formation process and physical-chemical properties of silica-titania monoliths. The characterization results show that the silica-titania monoliths possess a bimodal porous structure with well-dispersed titania inside silica network. The addition of titania in silica improves the thermal stability of both macroporous and mesoporous structures.

  4. Ferro- and piezoelectric properties of polar-axis-oriented CaBi4Ti4O15 films

    Science.gov (United States)

    Kato, Kazumi; Fu, Desheng; Suzuki, Kazuyuki; Tanaka, Kiyotaka; Nishizawa, Kaori; Miki, Takeshi

    2004-05-01

    Polar-axis-oriented CaBi4Ti4O15 (CBTi144) films were fabricated on Pt foils using a complex metal alkoxide solution. The 500-nm-thick film showed the columnar structure and consisted of well-developed grains. The a/b-axis orientation of the ferroelectric films is considered to be associated with the preferred orientation of Pt foil. The film showed good ferro- and piezoelectric properties. The Pr and Ec were 25 μC/cm2 and 306 kV/cm, respectively, at an applied voltage of 115 V. The d33 was characterized as 30 pm/V by piezoresponse force microscopy. The values were twice as large as those of the CBTi144 thin film with random orientation. The polar-axis-oriented CBTi144 films would open up possibilities for devices as Pb-free piezoelectric materials.

  5. Ferroelectric properties of alkoxy-derived CaBi4Ti4O15 thin films on Pt-passivated Si

    Science.gov (United States)

    Kato, Kazumi; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi

    2001-02-01

    CaBi4Ti4O15 (CBTi144) thin films were prepared by spin coating a precursor solution of metal alkoxides. As-deposited thin films began crystallization below 550 °C and reached full crystallinity of a single phase of layered perovskite at 650 °C via rapid thermal annealing in oxygen. The 650 °C annealed CBTi144 thin film showed random orientation on Pt-passivated Si substrate and exhibited P-E hysteresis loops. The remanent polarization (Pr) and coercive electric field (Ec) were 9.4 μC/cm2 and 106 kV/cm, respectively, at 11 V. The dielectric constant and loss factor were 300 and 0.033, respectively, at 100 kHz.

  6. Effects of BaBi2Ta2O9 thin buffer layer on crystallization and electrical properties of CaBi2Ta2O9 thin films on Pt-coated silicon

    Science.gov (United States)

    Kato, Kazumi; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi

    2001-05-01

    Non-c-axis oriented CaBi2Ta2O9 (CBT) thin films have been successfully deposited via the triple alkoxide solution method on Pt-coated Si substrates by inserting BaBi2Ta2O9 (BBT) thin buffer layers. The BBT thin buffer layer, which was prepared on Pt-coated Si, was a key material for suppression of the nonpolar c-axis orientation and promoting the ferroelectric structure perpendicular to the in-plane direction of CBT thin film. The annealing temperature and thickness of the BBT thin buffer layers affected the dielectric, ferroelectric, and fatigue properties of the stacked CBT/BBT thin films. The resultant 650 °C annealed CBT/BBT(30 nm) thin film exhibited good P-E hysteresis properties and fatigue behaviors.

  7. Bottom-up fabrication and piezoelectric properties of CaBi4Ti4O15 micro-plateaus

    Science.gov (United States)

    Kato, K.; Tanaka, K.; Kayukawa, S.; Suzuki, K.; Masuda, Y.; Kimura, T.; Nishizawa, K.; Miki, T.

    2007-08-01

    CaBi4Ti4O15 (CBTi144) micro-plateaus were fabricated on Si wafers and Pt foils using a self-assembled monolayer (SAM) and a complex metal alkoxide solution. The micro-plateaus are delineated by metal masks, which are used for shadowing against the ultraviolet (UV) irradiation for decomposition of SAM to make the surface hydrophilic. The micro-plateaus crystallized to a ferroelectric phase with random orientation. The crystallization depended on the SAM-derived ultra thin layers at the surface of the substrates. The primitive PFM measurements without any top electrodes confirmed that the micro-plateaus exhibited the piezoresponse behaviors. The piezoelectric constant, d33, had some distribution, and the maximum d33 was confirmed as about 45 pm/V, which is identical to the d33 of the polar-axis oriented CBTi144 thin films.

  8. Phase transition, ferroelectric, and dielectric properties of layer-structured perovskite CaBi3Ti3O12-δ thin films

    Science.gov (United States)

    Kato, Kazumi; Suzuki, Kazuyuki; Nishizawa, Kaori; Miki, Takeshi

    2001-07-01

    Thin films of a bismuth-based layer-structured perovskite compound with a number of oxygen octahedron along the c axis between Bi-O layers of three, CaBi3Ti3O12-δ, were prepared using a mixture solution of complex alkoxides. The films crystallized below 550 °C. The crystal structure and surface morphology of these films changed between 600 and 650 °C. The 650 °C-annealed thin film consisted of well-developed grains and exhibited polarization-electric hysteresis loops. The remanent polarization and coercive electric field were 8.5 μC/cm2 and 124 kV/cm, respectively, at 7 V. The dielectric constant and loss factor were about 250 and 0.048, respectively, at 100 kHz.

  9. Impact of oxygen ambient on ferroelectric properties of polar-axis-oriented CaBi4Ti4O15 films

    Science.gov (United States)

    Kato, Kazumi; Tanaka, Kiyotaka; Suzuki, Kazuyuki; Kimura, Tatsuo; Nishizawa, Kaori; Miki, Takeshi

    2005-03-01

    Polar-axis oriented CaBi4Ti4O15(CBTi144) films were fabricated on Pt foils using a complex metal alkoxide solution. The oxygen ambient during crystallization of the films impacted the crystal perfection, crystallite size, and the ferroelectric properties. The 500mm thick film crystallized in oxygen flow had single columnar structure and in-plane grain size of about 200nm. The Scherrer's crystallite diameter was calculated as about 110nm. The ferroelectric properties were improved. The Pr and Ec of the film enhanced as 33.6μC /cm2 and 357kV /cm, respectively, at an applied voltage of 50V. Voltage applied for full polarization switching was lowered by controlling oxygen stoichiometry of the film. Indeed, the polar-axis-oriented CBTi144 films would open up possibilities for devices as Pb-free ferroelectric materials.

  10. Structure and ferro-/piezoelectric properties of bimorph-shape CaBi4Ti4O15 films on Pt foils

    Science.gov (United States)

    Kato, K.; Tanaka, K.; Suzuki, K.; Kimura, T.; Nishizawa, K.; Miki, T.

    2005-04-01

    In-plane c-axis oriented CaBi4Ti4O15 (CBTi144) films were fabricated on Pt foils using a complex metal alkoxide solution. The a/b-axis orientation of the ferroelectric films was affected by the preferred orientation of Pt foil, which is associated with the thickness. The 500 nm-thick CBTi144 films showed good ferro- and piezoelectric properties on 0.010 mm-thick Pt foils. The Pr and Ec were 26 μC/cm2 and 230 kV/cm, respectively, at an applied voltage of 75 V. The d33 was characterized as 25-34 pm/V by piezoresponse force microscopy. The values enhanced compared to those of the CBTi144 thin film with random orientation. The polar-axis oriented CBTi144 films would open for novel devices as Pb-free piezoelectric materials.

  11. Nanocomposite organomineral hybrid materials. Part 2

    Directory of Open Access Journals (Sweden)

    KUDRYAVTSEV Pavel Gennadievich

    2016-04-01

    Full Text Available The paper addresses the issues of alkoxide method of sol-gel synthesis and non-hydrolytic method of sol-gel synthesis and colloidal method of sol-gel synthesis. The authors also consider an alternative approach based on the use of soluble silicates as precursors in the sol-gel technology, of nanocomposites. It was shown that nanocomposites can be produced through aerogels. The paper also analyzes the mixing technologies of nanocomposites preparation. It has been demonstrated the possibility to change the types of nano-phase which is used for obtaining nanocomposites in different approaches. Various models of packaging spherical, fibrous and layered nanoparticles, introduced into the structure of the nanocomposite, in the preparation thereof were examined.

  12. Thermodynamic modelling and aqueous chemistry in the CaO-Al2O3-SiO2-H2O system

    International Nuclear Information System (INIS)

    Atkinson, A.; Hearne, J.A.; Knights, C.F.

    1990-01-01

    The chemical properties of the CaO-Al 2 O 3 -SiO 2 -H 2 O system are important for understanding and predicting the long term behaviour of Portland cements. Solids of known average composition in this system have been synthesised by the co-hydrolysis of mixed alkoxides. The solids have been equilibrated with water at 25 0 C and the composition of the aqueous phase characterised. A thermodynamic model for the system has been developed by extending an earlier model to include aluminium compounds. The model accounts for most of the experimental data and predicts that the main influence of aluminium is to form a hydrogarnet solid solution of general composition C 3 AH 6-2x S x . The model can be used to predict the chemistry of hydrated cements. (author)

  13. Low-cost composites based on porous titania–apatite surfaces for the removal of patent blue V from water: Effect of chemical structure of dye

    Directory of Open Access Journals (Sweden)

    C. El Bekkali

    2016-11-01

    Full Text Available Hydroxyapatite/titania nanocomposites (TiHAp were synthesized from a mixture of a titanium alkoxide solution and dissolution products of a Moroccan natural phosphate. The simultaneous gelation and precipitation processes occurring at room temperature led to the formation of TiHAp nanocomposites. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2 were the major crystalline phases. The specific surface area of the nanocomposites increased with the TiO2 content. Resulting TiHAp powders were assessed for the removal of the patent blue V dye from water. Kinetic experiments suggested that a sequence of adsorption and photodegradation is responsible for discoloration of dye solutions. These results suggest that such hydroxyapatite/titania nanocomposites constitute attractive low-cost materials for the removal of dyes from industrial textile effluent.

  14. Selective Hydrogen Atom Abstraction via Induced Bond Polarization: The Direct -Arylation of Alcohols via Photoredox, HAT and Nickel Catalysis.

    Science.gov (United States)

    Twilton, Jack; Christensen, Melodie; DiRocco, Daniel A; Ruck, Rebecca T; Davies, Ian W; MacMillan, David William

    2018-02-28

    The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation protocol for the selective functionalization of alcohol -hydroxy C-H bonds. This approach employs zinc-mediated alcohol deprotonation to activate -hydroxy C-H bonds while simultaneously suppressing C-O bond formation by inhibiting formation of nickel alkoxide species. The use of Zn based Lewis acids also deactivates other hydridic bonds such as -amino and -oxy C-H bonds. This technology facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3-step synthesis of the Prozac exemplifies the utility of this new method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Effect of vanadium on the obtaining of the titanium dioxide by Sol-Gel Method; Efeito do vanadio na obtencao de dioxido de titanio pelo Metodo Sol-Gel

    Energy Technology Data Exchange (ETDEWEB)

    Granado, S.R.; Silva, D.W.; Lopes, S.A.; Cavalheiro, A.A., E-mail: sandrogranado02@gmail.com [Universidade Estadual de Mato Grosso do Sul (CPTREN/UEMS), Navirai, MS (Brazil). Centro de Pesquisas Tecnologicas em Recursos Naturais

    2011-07-01

    The obtaining of transition metal modified titanium dioxide (TiO{sub 2}) can be a promising path to promote changes in crystal structure of anatase phase in order to displace the band gap toward frequencies near to visible region. The insertion of the heterovalent ions such as vanadium can be shift the titanium coordination number in the anatase matrix, leading to important changes in the photonic characteristics of the material. In Sol-Gel method, the presence of the non alkoxide precursors can affects the stability of the solution and the gelifying process, with consequences on the characteristics of the material. In this work, it was investigated the effect of 5mol% of vanadium by thermal analysis of the dried gel and XRD and adsorption isotherm in the samples obtained at different temperatures. The decomposition steps of the precursor were associated to phase formation in the material, leading to conclusion that the presence of vanadium affects the stability of anatase phase. (author)

  16. Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

    Energy Technology Data Exchange (ETDEWEB)

    Suegama, P.H. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade de Sao Paulo, CP 61548, 05424-970 Sao Paulo, SP (Brazil); Sarmento, V.H.V. [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil); Montemor, M.F. [ICEMS, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Benedetti, A.V. [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil); de Melo, H.G.; Aoki, I.V. [Departamento de Engenharia Quimica, Escola Politecnica, Universidade de Sao Paulo, CP 61548, 05424-970 Sao Paulo, SP (Brazil); Santilli, C.V., E-mail: santilli@iq.unesp.b [Departamento Fisico-Quimica, Instituto de Quimica, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil)

    2010-07-15

    This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film.

  17. Using Phos-Tag in Western Blotting Analysis to Evaluate Protein Phosphorylation.

    Science.gov (United States)

    Horinouchi, Takahiro; Terada, Koji; Higashi, Tsunehito; Miwa, Soichi

    2016-01-01

    Protein phosphorylation has traditionally been detected by radioisotope phosphate labeling of proteins with radioactive ATP. Several nonradioactive assays with phosphorylation site-specific antibodies are now available for the analysis of phosphorylation status at target sites. However, due to their high specificity, these antibodies they cannot be used to detect unidentified phosphorylation sites. Recently, Phos-tag technology has been developed to overcome the disadvantages and limitations of phosphospecific antibodies. Phos-tag and its derivatives conjugated to biotin, acrylamide, or agarose, form alkoxide-bridged dinuclear metal complexes, which can capture phosphate monoester dianions bound to serine, threonine, and tyrosine residues, in an amino acid sequence-independent manner. Here, we describe our method, which is based on in vitro kinase assay and Western blotting analysis using biotinylated Phos-tag and horseradish peroxidase-conjugated streptavidin, to determine the sites of TRPC6 (transient receptor potential canonical 6) channel phosphorylated by protein kinase A.

  18. Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wayne Tikkanen

    2006-12-31

    The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replaced by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.

  19. Synthesis of a Pseudodisaccharide α-C-Glycosidically Linked to an 8-Alkylated Guanine

    Directory of Open Access Journals (Sweden)

    Jan Duchek

    2013-04-01

    Full Text Available The synthesis of stable guanofosfocin analogues has attracted considerable attention in the past 15 years. Several guanofosfocin analogues mimicking the three constitutional elements of mannose, ribose, and guanine were designed and synthesized. Interest in ether-linked pseudodisaccharides and 8-alkylated guanines is increasing, due to their potential applications in life science. In this article, a novel guanofosfocin analogue 6, an ether-linked pseudodisaccharide connected α-C-glycosidically to an 8-alkylated guanine, was synthesized in a 10-longest linear step sequence from known diol 13, resulting in an overall yield of 26%. The key steps involve the ring-opening of cyclic sulfate 8 by alkoxide generated from 7 and a reductive cyclization of 4-N-acyl-2,4-diamino-5-nitrosopyrimidine 19 to form compound 6.

  20. Electrolytic method to make alkali alcoholates using ion conducting alkali electrolyte/separator

    Science.gov (United States)

    Joshi, Ashok V [Salt Lake City, UT; Balagopal, Shekar [Sandy, UT; Pendelton, Justin [Salt Lake City, UT

    2011-12-13

    Alkali alcoholates, also called alkali alkoxides, are produced from alkali metal salt solutions and alcohol using a three-compartment electrolytic cell. The electrolytic cell includes an anolyte compartment configured with an anode, a buffer compartment, and a catholyte compartment configured with a cathode. An alkali ion conducting solid electrolyte configured to selectively transport alkali ions is positioned between the anolyte compartment and the buffer compartment. An alkali ion permeable separator is positioned between the buffer compartment and the catholyte compartment. The catholyte solution may include an alkali alcoholate and alcohol. The anolyte solution may include at least one alkali salt. The buffer compartment solution may include a soluble alkali salt and an alkali alcoholate in alcohol.

  1. Blue-Emitting Small Silica Particles Incorporating ZnSe-Based Nanocrystals Prepared by Reverse Micelle Method

    Directory of Open Access Journals (Sweden)

    Masanori Ando

    2007-01-01

    Full Text Available ZnSe-based nanocrystals (ca. 4-5 nm in diameter emitting in blue region (ca. 445 nm were incorporated in spherical small silica particles (20–40 nm in diameter by a reverse micelle method. During the preparation, alkaline solution was used to deposit the hydrolyzed alkoxide on the surface of nanocrystals. It was crucially important for this solution to include Zn2+ ions and surfactant molecules (thioglycolic acid to preserve the spectral properties of the final silica particles. This is because these substances in the solution prevent the surface of nanocrystals from deterioration by dissolution during processing. The resultant silica particles have an emission efficiency of 16% with maintaining the photoluminescent spectral width and peak wavelength of the initial colloidal solution.

  2. Highly functionalized and potent antiviral cyclopentane derivatives formed by a tandem process consisting of organometallic, transition-metal-catalyzed, and radical reaction steps.

    Science.gov (United States)

    Jagtap, Pratap R; Ford, Leigh; Deister, Elmar; Pohl, Radek; Císařová, Ivana; Hodek, Jan; Weber, Jan; Mackman, Richard; Bahador, Gina; Jahn, Ullrich

    2014-08-11

    A simple modular tandem approach to multiply substituted cyclopentane derivatives is reported, which succeeds by joining organometallic addition, conjugate addition, radical cyclization, and oxygenation steps. The key steps enabling this tandem process are the thus far rarely used isomerization of allylic alkoxides to enolates and single-electron transfer to merge the organometallic step with the radical and oxygenation chemistry. This controlled lineup of multiple electronically contrasting reactive intermediates provides versatile access to highly functionalized cyclopentane derivatives from very simple and readily available commodity precursors. The antiviral activity of the synthesized compounds was screened and a number of compounds showed potent activity against hepatitis C and dengue viruses. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Molecular precursors for the phase-change material germanium-antimony-telluride, Ge{sub 2}Sb{sub 2}Te{sub 5} (GST)

    Energy Technology Data Exchange (ETDEWEB)

    Harmgarth, Nicole; Zoerner, Florian; Engelhardt, Felix; Edelmann, Frank T. [Chemisches Institut, Otto-von-Guericke-Universitaet Magdeburg (Germany); Liebing, Phil [Laboratorium fuer Anorganische Chemie, ETH Zuerich (Switzerland); Burte, Edmund P.; Silinskas, Mindaugas [Institut fuer Mikro- und Sensorsysteme, Otto-von-Guericke-Universitaet Magdeburg (Germany)

    2017-10-04

    This review provides an overview of the precursor chemistry that has been developed around the phase-change material germanium-antimony-telluride, Ge{sub 2}Sb{sub 2}Te{sub 5} (GST). Thin films of GST can be deposited by employing either chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. In both cases, the success of the layer deposition crucially depends on the proper choice of suitable molecular precursors. Previously reported processes mainly relied on simple alkoxides, alkyls, amides and halides of germanium, antimony, and tellurium. More sophisticated precursor design provided a number of promising new aziridinides and guanidinates. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. A simple three step method for selective placement of organic groups in mesoporous silica thin films

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, Esteban A. [Gerencia Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Av. Gral Paz 1499 (B1650KNA) San Martín, Buenos Aires (Argentina); Llave, Ezequiel de la; Williams, Federico J. [Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, C1428EHA Buenos Aires (Argentina); Soler-Illia, Galo J.A.A., E-mail: galo.soler.illia@gmail.com [Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, C1428EHA Buenos Aires (Argentina); Instituto de Nanosistemas, Universidad Nacional de General San Martín, 25 de Mayo y Francia (1650) San Martín, Buenos Aires (Argentina)

    2016-02-01

    Selective functionalization of mesoporous silica thin films was achieved using a three step method. The first step consists in an outer surface functionalization, followed by washing off the structuring agent (second step), leaving the inner surface of the pores free to be functionalized in the third step. This reproducible method permits to anchor a volatile silane group in the outer film surface, and a second type of silane group in the inner surface of the pores. As a concept test we modified the outer surface of a mesoporous silica film with trimethylsilane (–Si–(CH{sub 3}){sub 3}) groups and the inner pore surface with propylamino (–Si–(CH{sub 2}){sub 3}–NH{sub 2}) groups. The obtained silica films were characterized by Environmental Ellipsometric Porosimetry (EEP), EDS, XPS, contact angle and electron microscopy. The selectively functionalized silica (SF) shows an amount of surface amino functions 4.3 times lower than the one-step functionalized (OSF) silica samples. The method presented here can be extended to a combination of silane chlorides and alkoxides as functional groups, opening up a new route toward the synthesis of multifunctional mesoporous thin films with precisely localized organic functions. - Highlights: • Selective functionalization of mesoporous silica thin films was achieved using a three step method. • A volatile silane group is anchored by evaporation on the outer film surface. • A second silane is deposited in the inner surface of the pores by post-grafting. • Contact angle, EDS and XPS measurements show different proportions of amino groups on both surfaces. • This method can be extended to a combination of silane chlorides and alkoxides functional groups.

  5. Structural characterisation and antibacterial activity of PP/TiO2 nanocomposites prepared by an in situ sol–gel method

    International Nuclear Information System (INIS)

    Bahloul, Walid; Mélis, Flavien; Bounor-Legaré, Véronique; Cassagnau, Philippe

    2012-01-01

    Graphical abstract: TEM micrograph of PP/TiO 2 nanocomposite materials (a) in situ PP/TiO 2 and (b) PP/TiO 2 (anatase). Highlights: ► Titanium alkoxide hydrolysis–condensation reactions during polypropylene processing. ► Inorganic domains diameter of around 10 nm. ► Interesting antibacterial activities compared to a dispersion of anatase TiO 2 . - Abstract: Polypropylene/titanium dioxide (PP/TiO 2 ) nanocomposites can be prepared using a novel method based on the hydrolysis–condensation reactions (sol–gel method) of titanium alkoxide inorganic precursors that have been premixed with polypropylene under molten conditions. The resultant nanocomposites were characterised by transmission electronic microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques showed the formation of the titanium oxi-hydroxide chemical structure (Ti x O y (OH) z ) with a diameter of approximately 10 nm in the polymer matrix. Furthermore, a condensation degree of around 17% was determined using XPS analysis. The antibacterial activity was tested according to the JIS Z 2801:2000 standard with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in the absence of light. Correlations between the microstructure and the chemical composition of PP/TiO 2 nanocomposites and the antibacterial properties of these nanocomposites were discussed. The structure of titanium oxi-hydroxide derivative particles (Ti x O y (OH) z ) within the polypropylene matrix has been shown to impact strongly on the antibacterial properties in comparison with the results obtained with a dispersion of anatase titanium dioxide into the PP.

  6. Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

    Science.gov (United States)

    Kapusuz, Derya; Durucan, Caner

    2017-07-01

    The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, 29 Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

  7. Molecular biology of demosponge axial filaments and their roles in biosilicification.

    Science.gov (United States)

    Weaver, James C; Morse, Daniel E

    2003-11-01

    For hundreds of years, the skeletal elements of marine and freshwater sponges have intrigued investigators with a diverse array of remarkably complex morphologies. Early studies of demosponge monaxonal megascleres revealed the presence of a central organic axial filament running their entire length. Until recently, however, the precise function of these axial filaments was largely unknown. The spicules from the temperate Eastern Pacific demosponge, Tethya aurantia, comprise approximately 75% of the dry weight of this species, facilitating the large-scale isolation and purification of the biosilica-associated proteins. Silicateins, the most abundant proteins comprising the axial filaments of these spicules, prove to be members of a well-known superfamily of proteolytic and hydrolytic enzymes and can be easily collected after silica demineralization with hydrofluoric acid. Consistent with these findings, the intact filaments are more than simple, passive templates; in vitro, they actively catalyze and spatially direct the hydrolysis and polycondensation of silicon alkoxides to yield silica at neutral pH and low temperature. Catalytic activity also is exhibited by the monomeric subunits obtained by disaggregation of the protein filaments and those produced from recombinant DNA templates cloned in bacteria. These proteins also can be used to direct the polymerization of organosilicon polymers (silicones) from the corresponding organically functionalized silicon alkoxides. Based on these observations, the silicateins are currently being used as models for the design of biomimetic agents with unique catalytic and structure-directing properties. The presence of axial filaments in a diversity of spicule types and the evolutionary implications of these findings are also discussed. Copyright 2003 Wiley-Liss, Inc.

  8. A New Role for CO2: Controlling Agent of the Anionic Ring-Opening Polymerization of Cyclic Esters

    KAUST Repository

    Varghese, Jobi K.

    2017-08-15

    Conventional anionic ring-opening of polymerization (AROP) of cyclic esters suffers from the nonselective and concomitant attack of the monomer and of the polymer chains by the growing active species, which results in polyester samples with uncontrolled molar masses and broad polydispersity due to the competition between propagation and transesterification reactions. In this report, we describe a new AROP system mediated by a controlled amount of CO2 which prevents transesterification reactions from occurring. Using lithium monomethyl diethylene glycoxide (MEEOLi) as initiator and 1.5 equiv of CO2, ε-caprolactone could be polymerized under truly “living” conditions in dichloromethane (DCM) at 70 °C, as evidenced by the control of molar masses, the narrow polydispersity indexes (Mn up to ∼40 kg/mol, Đ < 1.16), and also successful chain extension experiments. Lithium carbonate used as initiator in the presence of 0.5 equiv of CO2 afforded similar polymerization results. Experiments carried out with other alkoxide salts and solvents demonstrate that CO2 is indispensable as well as lithium and noncoordinating solvents for the suppression of transesterifications. A similar strategy was applied for the AROP of l-lactide (LLA). At −20 °C, LLA could be polymerized under living conditions with undetectable level of transesterification as demonstrated by MALDI-ToF analysis. To account for the polymerization mechanism occurring in the presence of a slight excess of CO2, we resorted to computational studies. It appears that a fast equilibrium takes place between two tetrameric aggregates, one dormant comprising four carbonates (RCO3Li)4, and an active one involving three carbonates and one alkoxide (RCO3Li)3(ROLi). The latter is shown to selectively ring-open cyclic ester without indulging in transesterifications like (ROLi)4 precursors.

  9. Structural evolution of silica nanoparticles in water-in- oil microemulsions

    International Nuclear Information System (INIS)

    Bush, A.J.; Bartlett, J.R.; Finnie, K.S.; Schultz, J.; Kong, L.; Larkin, M.; Barbe, C.J.

    2003-01-01

    Full text: The controlled release of drugs, encapsulated within nanoparticles, has been achieved by a variety of microencapsulation techniques, including, liposomes, hydrogels and polymeric materials, which are based on organic carrier systems. We have been studying inorganic nanoparticles as they possess several intrinsic advantages as drug carriers for in-vivo applications. In particular, they are biologically inert, intrinsically hydrophilic and exhibit a long shelf life in the 'dry' state. Recently, we have developed a suite of sol-gel techniques for producing nanoparticulate silica containing encapsulated bioactive species using water-in-oil microemulsions. The internal nanostructure of the gels (pore volume, size and tortuosity, and surface chemistry), which controls the release kinetics of the bioactive species, can be precisely tailored by varying such sol-gel processing parameters as the water-to-alkoxide ratio, pH, alkoxide concentration, ageing, and drying conditions. Prior to encapsulation of the drug it is vital to understand the mechanism of particle formation. The effect of processing parameters, such as the pH of the aqueous core on the mechanism and kinetics of reactions occurring during nanoparticle evolution, have been investigated. Scattering methods including SANS, SAXS and light scattering, in conjunction with complementary spectroscopic techniques, have been used to probe the evolution of silica nanoparticle structure during the hydrolysis and condensation of tetramethylorthosilicate (TMOS) within the aqueous core of the w/o microemulsions. Photon correlation spectroscopy has revealed the micelle diameter to be 10-12nm. Particle evolution at various pH was monitored using SANS and the rate of hydrolysis has been studied with FTIR, revealing that particle formation appears to be more rapid in base than in acid conditions

  10. Modificación superficial de aleaciones de base aluminio (anodizadas y no anodizadas mediante recubrimientos de sílice

    Directory of Open Access Journals (Sweden)

    García-Heras, M.

    2004-04-01

    Full Text Available Transparent and colourless silica coatings were deposited on anodising and non-anodising substrates of aluminium-base alloys (series 6063. Coatings were prepared by soLgel (dipping method from a silica alkoxide and a mixture of both silica alkoxide and silica alkylalkoxide. Preparations were optimised from viscosity, density, surface tension, and contact angle measurements. Densification was carried out at 60 and 120 °C. Reflectance attenuation of coated samples was analysed by UV-VIS-NIR spectroscopy. The results indicated that -10 % of attenuation is reached. Durability and resistance against degradation tests of the metal/coating system were undertaken by immersion into aqueous solutions. Electrochemical impedance measurements and potential corrosion of the metallic substrate for variable times were performed.

    Se han depositado recubrimientos transparentes e incoloros de sílice sobre sustratos anodizados y no anodizados de aleaciones de base aluminio (serie 6063. Los recubrimientos se prepararon por sol-gel (inmersión-extracción a partir de un alcóxido de silicio y de una mezcla de alcóxido y alquilalcóxido de silicio. La optimización de las fonnulaciones se basó en medidas de viscosidad, densidad, tensión superficial y ángulo de contacto. La densificación se llevó a cabo a 60 y 120 °C. La atenuación de la reflectancia luminosa de las muestras recubiertas se analizó por espectroscopia UV-VIS-IRP. Los resultados indicaron que se alcanza casi un 10 % de atenuación. Los ensayos de durabilidad y resistencia a la degradación del sistema metal/recubrimiento se realizaron por inmersión en disoluciones acuosas, aplicando medidas de impedancia electroquímica y del potencial de corrosión del sustrato metálico, para tiempos variables.

  11. Methacrylate bonding to zirconia by in situ silica nanoparticle surface deposition.

    Science.gov (United States)

    Oliveira-Ogliari, Aline; Collares, Fabrício M; Feitosa, Victor P; Sauro, Salvatore; Ogliari, Fabrício A; Moraes, Rafael R

    2015-01-01

    This study introduces an innovative method to enhance adhesion of methacrylate-based cements to yttria-stabilized zirconia (Y-TZP) by means of a silica-nanoparticle deposition process. Two alkoxide organic precursors, tetraethyl-orthosilicate (TEOS) and zirconium tert-butoxide (ZTB) were diluted in hexane at different concentrations in order to obtain several experimental materials to enhance deposition of a SiO(x) reactive layer to Y-TZP. This deposition was attained via sintering alkoxide precursors directly on pre-sintered zirconia (infiltration method—INF) or application on the surface of fully sintered zirconia (coating method—COA). Untreated specimens and a commercial tribochemical silica coating were also tested as controls and all the treated Y-TZP specimens were analyzed using SEM-EDX. Specimens were bonded using silane, adhesive and dual-cure luting cement and submitted to shear bond strength test after different water storage periods (24 h, 3-, 6- and 12-months). SEM-EDX revealed Y-TZP surface covered by silica nanoclusters. The morphology of silica-covered Y-TZP surfaces was influenced by sintering method, employed to deposit nanoclusters. High bond strength (MPa) was observed when using COA method; highest TEOS percentage achieved the greatest bond strengths to Y-TZP surface (36.7±6.3 at 24 h). However, bonds stability was dependent on ZTB presence (32.9±9.7 at 3 months; 32.3±7.1 at 6 months). Regarding INF method, the highest and more stable resin-zirconia bond strength was attained when using experimental solutions containing TEOS and no ZTB. Both sintering methods tested in this study were able to achieve a bonding performance similar to that of classic tribochemical strategies. This study demonstrates that it is possible to achieve a reliable and long-lasting bonding between yttria-stabilized zirconia ceramic and methacrylate-based cements when using this novel, simple, and cost-effective bonding approach. Copyright © 2014 Academy of Dental

  12. Sol-gel bonding of silicon wafers

    International Nuclear Information System (INIS)

    Barbe, C.J.; Cassidy, D.J.; Triani, G.; Latella, B.A.; Mitchell, D.R.G.; Finnie, K.S.; Short, K.; Bartlett, J.R.; Woolfrey, J.L.; Collins, G.A.

    2005-01-01

    Sol-gel bonds have been produced between smooth, clean silicon substrates by spin-coating solutions containing partially hydrolysed silicon alkoxides. The two coated substrates were assembled and the resulting sandwich fired at temperatures ranging from 60 to 600 deg. C. The sol-gel coatings were characterised using attenuated total reflectance Fourier transform infrared spectroscopy, ellipsometry, and atomic force microscopy, while the corresponding bonded specimens were investigated using scanning electron microscopy and cross-sectional transmission electron microscopy. Mechanical properties were characterised using both microindentation and tensile testing. Bonding of silicon wafers has been successfully achieved at temperatures as low as 60 deg. C. At 300 deg. C, the interfacial fracture energy was 1.55 J/m 2 . At 600 deg. C, sol-gel bonding provided superior interfacial fracture energy over classical hydrophilic bonding (3.4 J/m 2 vs. 1.5 J/m 2 ). The increase in the interfacial fracture energy is related to the increase in film density due to the sintering of the sol-gel interface with increasing temperature. The superior interfacial fracture energy obtained by sol-gel bonding at low temperature is due to the formation of an interfacial layer, which chemically bonds the two sol-gel coatings on each wafer. Application of a tensile stress on the resulting bond leads to fracture of the samples at the silicon/sol-gel interface

  13. Synthesis of some pyridine and pyrimidine derivatives via Michael-Addition

    International Nuclear Information System (INIS)

    El-Baih, Fatma E.M.; Al-Rasheed, Hessa H.; Al-Hazimi, Hassan M.

    2006-01-01

    Synthesis of pyridine and pyrimidine analogues 4 and 6-9 were achieved by Michael-addition of compounds containing either active methylene groups like, malononitrile , ethyl cyanoacetate and 1-tetralone or compounds containing active hydrogen atoms like, guanidine in the presence of an oxidizing agent and thiourea to 2-arylmethylidine-1-tetralone and 2-arylmethylidine-6-methoxy-1-tetralone (2) (enones). Addition of malononitrile in piperidine at room temperature to 2-amino-3-cyno-naphtho [1, 2-malonoitrile in sodium alkoxide or sodium hydroxide to 2 gave 4. Cyclization of 3a with acetic anhydride in the presence of conc. H2sO4 gave the naphtha-pyrano[2, 3-d]pyrimidin-8-one (5). Condensation of the pyrimidine thione derivatives 9 with chloroacetic acid gave the 3-oxobenzo[h]thiazoladino[2, 3-b]quinazoline derivatives (10), which were reacted through their active methylene groups with aromatic aldehydes to give the arylidine derivatives 11. These compounds were also prepared in one step by reacting 9 with chloroacetic acid and aromatic aldehydes. Condensation of 9 with 3-bromopropanoic acid gave 4-oxo-benzo[h]1, 3-thiazino[2, 3-b]quinazoline derivatives (12). The structures of the prepared compounds were mainly confirmed on the basis of spectroscopic methods. (author)

  14. Incorporation of Nanohybrid Films of Silica into Recycled Polystyrene Matrix

    Directory of Open Access Journals (Sweden)

    Genoveva Hernández-Padrón

    2015-01-01

    Full Text Available An alternative for the reutilization of polystyrene waste containers consisting in creating a hybrid material made of SiO2 nanoparticles embedded in a matrix of recycled polystyrene (PSR has been developed. Recycled polystyrene functionalized (PSRF was used to influence the morphological and antifog properties by the sol-gel synthesis of nanohybrid silica. To this end, silica nanoparticles were produced from alkoxide precursors in the presence of recycled polystyrene. The functionalization of this polymeric matrix was with the purpose of uniting in situ carboxyl and silanol groups during the sol-gel process. In this way, opaque or transparent solid substrates can be obtained, with each of these endowed with optical conditions that depend on the amount of reactants employed to prepare each nanohybrid specimen. The nanohybrids were labelled as SiO2/PSR (HPSR and SiO2/PSRF (HPSRF and their properties were then compared to those of commercial polystyrene (PS. All the prepared samples were used for coating glass substrates. The hydrophobicity of the resultant coatings was determined through contact angle measurement. The nanohybrid materials were characterized by FT-IR and 1H-NMR techniques. Additionally, TGA and SEM were employed to determine their thermal and textural properties.

  15. Time effects on the stability of the induced defects in TiO2 nanoparticles doped by different nitrogen sources

    Science.gov (United States)

    Spadavecchia, F.; Ardizzone, S.; Cappelletti, G.; Oliva, C.; Cappelli, S.

    2012-12-01

    N-doped TiO2 samples are claimed to be the most promising among the so-called second-generation photocatalysts, but their success in photocatalysis is still under debate. In this study, N-doped TiO2 nanocrystals are obtained by a simple, quick, and effortless procedure, starting from titanium alkoxide as the precursor for the sol-gel route, with the N source being either inorganic (NH3) or organic (triethylamine, urea). Structural, morphological, and optical characterizations are compared with electron paramagnetic resonance (EPR) data to give an integrated picture of such materials. No literature data on the "aging" features in the dry state of the fresh calcined samples on the EPR and diffuse reflectance spectra (DRS) measurements are reported. Our N-doped TiO2 powders show different stabilities of paramagnetic and optical signals. The photocatalytic activity is tested, toward the degradation of ethanol in aqueous media, under both visible and UV irradiation, in this latter case resembling the same trend of the paramagnetic species decay.

  16. High dose thermoluminescence dosimetry performance of Sol-gel synthesized TiO{sub 2} phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Salas J, Ch. J.; Cruz V, C. [Universidad de Sonora, Departamento de Investigacion en Polimeros y Materiales, Apdo. Postal 130, 83000 Hermosillo, Sonora (Mexico); Castillo U, D. M.; Flores M, K. [Universidad de Sonora, Departamento de Ciencias Quimico Biologicas, Apdo. Postal 130, 83000 Hermosillo, Sonora (Mexico); Bernal, R. [Universidad de Sonora, Departamento de Investigacion en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico); Castano, V. M., E-mail: castillouzeta@gmail.com [UNAM, Instituto de Fisica, Centro de Fisica Aplicada y Tecnologia Avanzada, Apdo. Postal 1-1010, Queretaro, Qro. (Mexico)

    2015-10-15

    Full text: TiO{sub 2} is a ceramic material with many applications due to their different crystalline phases (rutile, anatase and brookite). It has attracted attention in several fields because their high mechanical strength, chemical stability and ion-conducting properties. Moreover, in recent years, some research groups gained interest in the thermoluminescence features of TiO{sub 2} concerning their potential use as thermoluminescence dosimeter. In this work, we present experimental results obtained in the first stage of a long-term research project focused in the synthesis of TiO{sub 2} phosphors for dosimetric applications. The thermoluminescent characterization of samples was carried out after being exposed to beta particle irradiation. TiO{sub 2} was prepared by alkoxide sol-gel route using titanium tetrabutoxide as precursor, ethanol, water and ammonia as catalyst. Pellet-shaped samples were annealed at 700 degrees C for 6 h in air atmosphere followed by slow cooling, and then were exposed to radiation doses from 25 to 400 Gy. The glow curves display maxima located at 103 and 238 degrees C when a 5 C/s heating rate is used. From the experimental results here presented, we conclude that TiO{sub 2} is a promising material to develop high dose Tl dosimeters. (Author)

  17. Visible light sensitized attapulgite-based lanthanide composites: microstructure, photophysical behaviour and biological application.

    Science.gov (United States)

    Xu, Jun; Sun, Zhihong; Jia, Lei; Li, Bo; Zhao, Long; Liu, Xiao; Ma, Yufei; Tian, Hao; Wang, Qin; Liu, Weisheng; Tang, Yu

    2011-12-28

    Attapulgite, an extremely stable fibrillar mineral present in nature, is a promising new carrier of luminescent lanthanide complexes for further applications. A europium complex Eu(DBM)(3)(H(2)O)(2) (HDBM = dibenzoylmethane) was covalently coupled onto modified attapulgites (or silica nanoparticles) via a ligand exchange reaction, generating attapulgite-based ternary europium complexes. The composites were characterized by CHN elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) for Eu(3+) content, powder X-ray diffraction (XRD), thermogravimetry (TG) and UV-vis absorption spectra. The results indicate that the Eu(3+) complex was grafted covalently to the outer surfaces of attapulgites (or silica nanoparticles) and modifications by coupling agents containing different alkoxide groups (aminopropyltriethoxysilane (APTES) or aminopropylmethyldiethoxysilane (APMDES)) led to different grafting ratios. The structures of these composites were further evidenced by the determination of photophysical behaviours and coordinated water molecules of the complexes linked to matrices. Attapulgite-based lanthanide composites linked by APTES can be excited by visible light, with a wide excitation wavelength range from UV to visible light (a maximum at 398 nm), long luminescence lifetime (503 μs), high quantum yield (48%) and improved exposure durability. When incubated with HeLa cells at 37 °C, the fluorescence of matrix-APTES-cpa-Eu(DBM)(3) is observed on the cell membrane. Moreover, the low cytotoxicity of our present system results in potential applications for cell imaging in biological systems. This journal is © The Royal Society of Chemistry 2011

  18. Photoconductivity, photoluminescence and optical Kerr nonlinear effects in zinc oxide films containing chromium nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Torres, C., E-mail: crstorres@yahoo.com.mx [Seccion de Estudios de Posgrado e Investigacion, ESIME-Z, Instituto Politecnico Nacional, Mexico, DF 07738 (Mexico); Garcia-Cruz, M.L. [Centro de Investigacion en Dispositivos Semiconductores, Benemerita Universidad Autonoma de Puebla, A. P. J-48, Puebla 72570, Mexico (Mexico); Castaneda, L., E-mail: luisca@sirio.ifuap.buap.mx [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, A. P. J-48, Puebla 72570, Mexico (Mexico); Rangel Rojo, R. [CICESE/Depto. de Optica, A. P. 360, Ensenada, BC 22860 (Mexico); Tamayo-Rivera, L. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, DF 01000 (Mexico); Maldonado, A. [Depto. de Ing. Electrica, CINVESTAV IPN-SEES, A. P. 14740, Mexico DF 07000 (Mexico); Avendano-Alejo, M., E-mail: imax_aa@yahoo.com.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, A. P. 70-186, 04510, DF (Mexico); and others

    2012-04-15

    Chromium doped zinc oxide thin solid films were deposited on soda-lime glass substrates. The photoconductivity of the material and its influence on the optical behavior was evaluated. A non-alkoxide sol-gel synthesis approach was used for the preparation of the samples. An enhancement of the photoluminescence response exhibited by the resulting photoconductive films with embedded chromium nanoclusters is presented. The modification in the photoconduction induced by a 445 nm wavelength was measured and then associated with the participation of the optical absorptive response. In order to investigate the third order optical nonlinearities of the samples, a standard time-resolved Optical Kerr Gate configuration with 80 fs pulses at 830 nm was used and a quasi-instantaneous pure electronic nonlinearity without the contribution of nonlinear optical absorption was observed. We estimate that from the inclusion of Cr nanoclusters into the sample results a strong optical Kerr effect originated by quantum confinement. The large photoluminescence response and the important refractive nonlinearity of the photoconductive samples seem to promise potential applications for the development of multifunctional all-optical nanodevices. - Highlights: Black-Right-Pointing-Pointer Enhancement in photoluminescence for chromium doped zinc oxide films is presented. Black-Right-Pointing-Pointer A strong and ultrafast optical Kerr effect seems to result from quantum confinement. Black-Right-Pointing-Pointer Photoconductive properties for optical and optoelectronic functions were observed.

  19. Encapsulation of titanium dioxide nanoparticles in PLA microspheres using supercritical emulsion extraction to produce bactericidal nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Campardelli, R., E-mail: rcampardelli@unisa.it; Della Porta, G. [University of Salerno, Department of Industrial Engineering (Italy); Gomez, V.; Irusta, S. [University of Zaragoza, Aragon Institute of Nanoscience (INA) (Spain); Reverchon, E., E-mail: ereverchon@unisa.it [University of Salerno, Department of Industrial Engineering (Italy); Santamaria, J., E-mail: jesus.santamaria@unizar.es [University of Zaragoza, Aragon Institute of Nanoscience (INA) (Spain)

    2013-10-15

    In this work, PLA microparticles containing TiO{sub 2} (anatase) nanoparticles have been produced using the Continuous Supercritical Emulsion Extraction technique (SEE-C). A stabilized anatase colloidal suspension (15 {+-} 5 nm) in ethanol aqueous solution was obtained by precipitation from solutions of titanium alkoxides and directly used as the water internal phase of a water-in-oil in water double emulsion or suspended as a powder in the organic phase of a solid-in-oil in water emulsion. Micro- (0.9 {+-} 0.5 {mu}m) and submicro-particles (203 {+-} 40 nm) have been produced, with TiO{sub 2} nominal loadings of 1.2, 2.4, and 3.6 wt%. High TiO{sub 2} encapsulation efficiencies up to about 90 % have been obtained. PLA/TiO{sub 2} particles have been characterized by TEM and XPS to investigate the dispersion of the metal oxide in the polymeric matrix. The photo-assisted bactericidal activity of TiO{sub 2}-containing microparticles against a biofilm-forming strain of Staphylococcus aureus was investigated in specific assays under UV light. Pure TiO{sub 2} nanoparticles and PLA/TiO{sub 2} particles showed the same bactericidal activity.

  20. New inorganic (an)ion exchangers with a higher affinity for arsenate and a competitive removal capacity towards fluoride, bromate, bromide, selenate, selenite, arsenite and borate

    KAUST Repository

    Chubar, Natalia

    2011-12-01

    Highly selective materials and effective technologies are needed to meet the increasingly stronger drinking water standards for targeted ionic species. Inorganic ion exchangers based on individual and mixed-metal hydrous oxides (or mixed adsorbents that contain inorganic ion exchangers in their composition) are adsorptive materials that are capable of lowering the concentrations of anionic contaminants, such as H 2AsO 4 -, H 3AsO 3, F -, Br -, BrO 3 -, HSeO 4 -, HSeO 3 - and H 3BO 3, to 10 μg/L or less. To achieve a higher selectivity towards arsenate, a new ion exchanger based on Mg-Al hydrous oxides was developed by a novel, cost-effective and environmentally friendly synthesis method via a non-traditional (alkoxide-free) sol-gel approach. The exceptional adsorptive capacity of the Mg-Al hydrous oxides towards H 2AsO 4 - (up to 200 mg[As]/gdw) is due to the high affinity of this sorbent towards arsenate (steep equilibrium isotherms) and its fast adsorption kinetics. Because of the mesoporous (as determined by N 2 adsorption and SEM) and layered (as determined by XRD and FTIR) structure of the ion-exchange material as well as the abundance of anion exchange sites (as determined by XPS and potentiometric titration) on its surface the material demonstrated very competitive (or very high) removal capacity towards other targeted anions, including fluoride, bromide, bromate, selenate, selenite, and borate. © 2011 IWA Publishing.

  1. Effect of Precursor Concentration of MgO nanostructure by using Sol-Gel Method

    Directory of Open Access Journals (Sweden)

    V.T. Srisuvetha

    2017-04-01

    Full Text Available MgO thin flims have been prepared on substrates by a novel and simple sol-gel method using magnesium nitrate and collusion as starting material.The MgO nano catalyst with good sensor crystallization were obtained after annealing at 100°C Magnesium oxide was prepared by sol-gel method. The method involves the hydrolysis of magnesium alkoxide in the presence of acid or basic catalysts followed by a Oxalic acid reaction. The synthesized solids were characterized by IR spectroscopy X-ray diffraction electron microscopy. Ultraviolet visible absorbance measurement photoluminescence and Raman scattering spectra. X-ray diffraction (XRD characterization showed the formation of smaller particles after sol gel irradiation the structure and morphology of the MgO particles were analyzed byXRD. These articles were used for FTIR spectroscopic measurement and spectra were collected. In EDS we calculated the peak intensity the SEM the images of metal oxide.UV (Ultra Violet refers to adsorption spectroscopy optical properties of assorption, band gap energy.This means if use light in the visible and adjacent ranges.

  2. Phthalocyanine/chitosan-TiO{sub 2} photocatalysts: Characterization and photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Hamdi, A. [University of Sfax-Faculty of Science-LCI-Sfax-Tunisia (Tunisia); Boufi, S. [University of Sfax-Faculty of Science-LMSE-Sfax-Tunisia (Tunisia); Bouattour, S., E-mail: soraa.boufi@yahoo.com [University of Sfax-Faculty of Science-LCI-Sfax-Tunisia (Tunisia)

    2015-06-01

    Graphical abstract: - Highlights: • Hybrid chitosan–phthalocyanine-TiO{sub 2} photocatalyst are elaborated at room temperature without any calcination treatment. • After immersion in water, the alkoxide groups underwent hydrolysis and the (TiO{sub 6}) octahedra started to join together. • The enhanced activity of the hybrid catalyst is attributed to the cooperative role of the three components of the photocatalyst. - Abstract: Chitosan (CS) was used as a template to prepare a hybrid chitosan–phthalocyanine-TiO{sub 2} (PC/CS-TiO{sub 2}) photocatalyst at room temperature without any calcination treatment. The as-prepared hybrid photocatalyst (PC/CS-TiO{sub 2}) was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and UV–vis diffuse reflectance spectroscopy (DRS). The results of the photodegradation of aniline, used as a model pollutant, revealed that the hybrid photocatalyst (PC/CS-TiO{sub 2}) exhibited a photocatalytic activity under visible-light irradiation. The enhanced activity of the hybrid catalyst is attributed to the cooperative role of the three components of the photocatalyst; chitosan as a template for the immobilization crystalline TiO{sub 2} nanoparticles, phthalocyanine that promote the light absorption in the visible range and TiO{sub 2} acting as an acceptor of electrons generated by the photons absorption to produce superoxide radicals.

  3. Synthesis and Characterization of Upconversion Fluorescent Yb3+, Er3+ Doped CsY2F7 Nano- and Microcrystals

    Directory of Open Access Journals (Sweden)

    Helmut Schäfer

    2009-01-01

    Full Text Available Cs Y2F7: 78%   Y3+, 20%   Yb3+, 2%   Er3+ nanocrystals with a mean diameter of approximately 8 nm were synthesized at   185°C in the high boiling organic solvent N-(2-hydroxyethyl-ethylenediamine (HEEDA using ammonium fluoride, the rare earth chlorides and a solution of caesium alkoxide of N-(2-hydroxyethyl-ethylenediamine in HEEDA. In parallel with this approach, a microwave assisted synthesis was carried out which forms nanocrystals of the same material, about 50 nm in size, in aqueous solution at 200∘C/8 bar starting from ammonium fluoride, the rare earth chlorides, and caesium fluoride. In case of the nanocrystals, derived from the HEEDA synthesis, TEM images reveal that the particles are separated but have a broad size distribution. Also an occurred heat-treatment of these nanocrystals (600∘C for 45 minutes led to bulk material which shows highly efficient light emission upon continuous wave (CW excitation at 978 nm. Besides the optical properties, the structure and the morphology of the three products were investigated by means of powder XRD and Rietveld method.

  4. Thermal plasma fabricated lithium niobate-tantalate films on sapphire substrate

    International Nuclear Information System (INIS)

    Kulinich, S.A.; Yoshida, T.; Yamamoto, H.; Terashima, K.

    2003-01-01

    We report the deposition of LiNb 1-x Ta x O 3 (0≤x≤1) films on (001) sapphire substrates in soft vacuum using a radio frequency thermal plasma. The growth rate, crystallinity, c-axis orientation, and surface roughness were examined as functions of substrate temperature, precursor feed rate, and substrate surface condition. The film Nb/Ta ratio was well controlled by using an appropriate uniform mixture of lithium-niobium and lithium-tantalum alkoxide solutions. The epitaxy and crystallinity of the films were much improved when the film growth rate was raised from 20 to 180-380 nm/min, where the films with the (006) rocking curve full width at half maximum values as low as 0.12 deg. -0.2 deg. could be produced. The film roughness could be reduced by using a liquid precursor with higher metal concentrations, achieving the root-mean-square value on the order of 5 nm. The refractive indices of the films are in good correspondence with their composition and crystallinity

  5. Preparation and Investigation of the Thermal Stability of Phosphate-modified TiO2 Anatase Powders and Thin Films.

    Science.gov (United States)

    Prah, Uroš; Škofic, Irena Kozjek

    2017-12-01

    The temperature dependence of the anatase-to-rutile phase transition of TiO2 powders and thin films was studied. In order to shift the phase transition to higher temperature, samples were doped with a different amount of phosphate ions and their influence on the structure and thermal stability of the anatase phase was investigated. In addition, the effect of the catalyst form (powders or thin films) on the temperature of the anatase-to-rutile phase transition was observed. TiO2 thin films and powders were prepared using a simple sol-gel method with an alkoxide precursor and citric acid. The thin films were deposited on silicon and aluminum substrates using the dip-coating technique. The content of the anatase phase and the crystallite size at different annealing temperatures were monitored using X-ray diffraction. The course of the thermal decomposition was followed using thermal analyses. The morphology, particle size, shape and elemental makeup of the samples were investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the phosphate ions successfully inhibited the growth of the anatase nanoparticles and delayed the phase transition to the rutile phase.

  6. Sol-gel processing of glasses and glass-ceramics for microelectronic packaging

    International Nuclear Information System (INIS)

    Sriram, M.A.; Kumta, P.N.

    1992-01-01

    In recent years considerable progress has been made in electronic packaging substrate technology. The future need of miniaturization of devices to increase the signal processing speeds calls for an increase in the device density requiring the substrates to be designed for better thermal, mechanical and electrical efficiency. Fast signal propagation with minimum delay requires the substrate to possess very low dielectric constant. Several glasses and glass-ceramic materials have been identified over the years which show good promise as candidate substrate materials. among these borophosphate and borophosphosilicate glass-ceramics have been recently identified to have the lowest dielectric constant. This paper reports that sol-gel processing has been used to synthesize borosilicate, borophosphosilicate and borophosphate glasses and glass-ceramics using inexpensive boron oxide and phosphorus pentoxide precursors. Preliminary results of the processing of these gels and the effect of volatility of boron alkoxide and its modification on the gel structure are described. X-ray diffraction, Differential thermal analyses and FTIR have been used to characterize the as-prepared and heat treated gels

  7. Development of Advanced Materials for Electro-Ceramic Application Final Report CRADA No. TC-1331-96

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Olstad, R. [General Atomics, San Diego, CA (United States); McMillan, L. [Symetrix International, Inc., Colorado Springs, CO (United States); Tulupov, A. [Soliton-NTT, Moscow (Russia)

    2017-10-19

    The goal of this project was to further develop and characterize the electrochemical methods originating in Russia for producing ultra high purity organometallic compounds utilized as precursors in the production of high quality electro-ceramic materials. Symetrix planned to use electro-ceramic materials with high dielectric constant for microelectronic memory circuit applications. General Atomics planned to use the barium titanate type ceramics with low loss tangent for producing a high power ferroelectric tuner used to match radio frequency power into their Dill-D fusion machine. Phase I of the project was scheduled to have a large number of organometallic (alkoxides) chemical samples produced using various methods. These would be analyzed by LLNL, Soliton and Symetrix independently to determine the level of chemical impurities thus verifying each other's analysis. The goal was to demonstrate a cost-effective production method, which could be implemented in a large commercial facility to produce high purity organometallic compounds. In addition, various compositions of barium-strontium-titanate ceramics were to be produced and analyzed in order to develop an electroceramic capacitor material having the desired characteristics with respect to dielectric constant, loss tangent, temperature characteristics and non-linear behavior under applied voltage. Upon optimizing the barium titanate material, 50 capacitor preforms would be produced from this material demonstrating the ability to produce, in quantity, the pills ultimately required for the ferroelectric tuner (approx 2000-3000 ceramic pills).

  8. Synthesis of mesoporous NiO nanospheres as anode materials for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhang Guanhua; Chen Yuejiao; Qu Baihua; Hu Lingling; Mei Lin; Lei Danni; Li Qing; Chen Libao; Li Qiuhong; Wang Taihong

    2012-01-01

    In this work, three-dimensional mesoporous NiO nanostructures have been synthesized by a simple ethylene glycol (EG)-mediated self-assembly route and subsequent calcination process. The synthesized nickel alkoxide precursors annealed at 300 and 500 °C exhibit different surface area, crystallinity and pore distribution, which have been characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, Fourier transform infrared spectroscopy and Nitrogen adsorption/desorption isotherms. The electrochemical properties of these NiO mesoporous nanostructures are investigated including the cycling and rate performance as anode materials for lithium-ion batteries. It is indicated that mesoporous NiO nanospheres synthesized at 500 °C exhibit better electrochemical performance than that obtained at 300 °C. The NiO nanospheres annealed at 500 °C present a reversible specific capacity of 518 mAh g −1 at a current density of 0.1 A g −1 after 60 cycles. With varying the rate from 0.1 to 8.0 A g −1 , the capacity remains at 535 mAh g −1 at 2 A g −1 after 30 cycles and resumes to 582 mAh g −1 at 0.1 A g −1 after 60 cycles. The results indicate that our mesoporous NiO nanospheres are promising anode materials for lithium ion batteries.

  9. Facile Sol-Gel Derived Crater-like Dual-functioning TiO2 Electron Transport Layer for High Efficiency Perovskite Solar Cells.

    Science.gov (United States)

    Ma, Sunihl; Ahn, Jihoon; Oh, Yunjung; Kwon, Hyeok-Chan; Lee, Eunsong; Kim, Kyungmi; Yun, Seong-Cheol; Moon, Jooho

    2018-04-05

    Organic-inorganic hybrid perovskite solar cells (PSCs) are considered promising materials for low-cost solar energy harvesting technology. An electron transport layer (ETL), which facilitates the extraction of photo-generated electrons and their transport to the electrodes, is a key component in planar perovskite solar cells. In this study, a new strategy to concurrently manipulate the electrical and optical properties of ETLs to improve the performance of PSCs is demonstrated. A careful control over the Ti alkoxide-based sol-gel chemistry leads to a crater-like porous/blocking bilayer TiO2 ETL with relatively uniform surface pores of 220 nm diameter. Additionally, the phase separation promoter added to the precursor solution enables nitrogen doping in the TiO2 lattice, thus generating oxygen vacancies. The crater-like surface morphology allows for better light transmission due to reduced reflection, while the electrically conductive crater-like bilayer ETL enhances charge extraction and transport. Through these synergetic improvements in both optical and electrical properties, the power conversion efficiency of crater-like bilayer TiO2 ETL-based PSCs could be increased from 13.7% to 16.0% as compared to conventional dense TiO2-based PSCs.

  10. An orthogonal ferromagnetically coupled tetracopper(II) 2 x 2 homoleptic grid supported by micro-O4 bridges and its DFT study.

    Science.gov (United States)

    Roy, Somnath; Mandal, Tarak Nath; Barik, Anil Kumar; Pal, Sachindranath; Butcher, Ray J; El Fallah, Mohamed Salah; Tercero, Javier; Kar, Susanta Kumar

    2007-03-28

    A pyrazole based ditopic ligand (PzOAP), prepared by the reaction between 5-methylpyrazole-3-carbohydrazide and methyl ester of imino picolinic acid, reacts with Cu(NO3)2.6H2O to form a self-assembled, ferromagnetically coupled, alkoxide bridged tetranuclear homoleptic Cu(II) square grid-complex [Cu4(PzOAP)4(NO3)2] (NO3)2.4H2O (1) with a central Cu4[micro-O4] core, involving four ligand molecules. In the Cu4[micro-O4] core, out of four copper centers, two copper centers are penta-coordinated and the remaining two are hexa-coordinated. In each case of hexa-coordination, the sixth position is occupied by the nitrate ion. The complex 1 has been characterized structurally and magnetically. Although Cu-O-Cu bridge angles are too large (138-141 degrees) and Cu-Cu distances are short (4.043-4.131 A), suitable for propagation of expected antiferromagnetic exchange interactions within the grid, yet intramolecular ferromagnetic exchange (J = 5.38 cm(-1)) is present with S = 4/2 magnetic ground state. This ferromagnetic interaction is quite obvious from the bridging connections (d(x2-y2)) lying almost orthogonally between the metal centers. The exchange pathways parameters have been evaluated from density functional calculations.

  11. Thermochemical Stability and Friction Properties of Soft Organosilica Networks for Solid Lubrication

    Directory of Open Access Journals (Sweden)

    Pablo Gonzalez Rodriguez

    2018-01-01

    Full Text Available In view of their possible application as high temperature solid lubricants, the tribological and thermochemical properties of several organosilica networks were investigated over a range of temperatures between 25 and 580 °C. Organosilica networks, obtained from monomers with terminal and bridging organic groups, were synthesized by a sol-gel process. The influence of carbon content, crosslink density, rotational freedom of incorporated hydrocarbon groups, and network connectivity on the high temperature friction properties of the polymer was studied for condensed materials from silicon alkoxide precursors with terminating organic groups, i.e., methyltrimethoxysilane, propyltrimethoxysilane, diisopropyldimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane and 4-biphenylyltriethoxysilane networks, as well as precursors with organic bridging groups between Si centers, i.e., 1,4-bis(triethoxysilylbenzene and 4,4′-bis(triethoxysilyl-1,1′-biphenyl. Pin-on-disc measurements were performed using all selected solid lubricants. It was found that materials obtained from phenyltrimethoxysilane and cyclohexyltrimethoxysilane precursors showed softening above 120 °C and performed best in terms of friction reduction, reaching friction coefficients as low as 0.01. This value is lower than that of graphite films (0.050 ± 0.005, a common bench mark for solid lubricants.

  12. Thermoluminescent dosimetry of beta radiations of 90 Sr/ 90 Y using amorphous ZrO2

    International Nuclear Information System (INIS)

    Rivera M, T.; Olvera T, L.; Azorin N, J.; Barrera R, M.; Soto E, A.M.

    2005-01-01

    In this work the results of studying the thermoluminescent properties (Tl) of the zirconium oxide in its amorphous state (ZrO 2 -a) before beta radiations of 90 Sr/ 90 Y are presented. The amorphous powders of the zirconium oxide were synthesized by means of the sol-gel technique. The sol-gel process using alkoxides like precursors, is an efficient method to prepare a matrix of zirconium oxide by hydrolysis - condensation of the precursor to form chains of Zr-H 3 and Zr-O 2 . One of the advantages of this technique is the obtention of gels at low temperatures with very high purity and homogeneity. The powders were characterized by means of thermal analysis and by X-ray diffraction. The powders of ZrO 2 -a, previously irradiated with beta particles of 90 Sr/ 90 Y, presented a thermoluminescent curve with two peaks at 150 and 257 C. The dissipation of the information of the one ZrO 2 -a was of 40% the first 2 hours remaining constant the information for the following 30 days. The reproducibility of the information was of ± 2.5% in standard deviation. The studied characteristics allow to propose to the amorphous zirconium oxide as thermoluminescent dosemeter for the detection of beta radiation. (Author)

  13. Synthesis of nano-sized MgO particle and thin film from diethanolamine-stabilized magnesium-methoxide

    International Nuclear Information System (INIS)

    Jung, Hyun Suk; Lee, J.-K.; Young Kim, J.; Hong, Kug Sun

    2003-01-01

    The effects of diethanolamine (DEA) addition on the crystallization behavior of magnesium methoxide and the stabilization behavior of the Mg-alkoxide were investigated using differential scanning calorimetry, thermogravimetry, X-ray powder diffraction, transmission electron microscopy, and X-ray photoemission spectroscopy. 20 mol% DEA additions to magnesium methoxide showed enhanced stability such that a time-dependent change in the sol was not observed in air. Moreover, the DEA addition enhanced the crystallization process. Crystalline MgO in the 20 mol% of DEA-added magnesium methoxide powder was observed at 300 deg. C for samples processed in O 2 and a high degree of crystallinity was observed at 400 deg. C when processed in O 2 . The enhanced crystallization of Mg-methoxide with added DEA in O 2 is discussed in terms of structural relaxation and heat generation during the ignition of an organic species of DEA. Using a DEA added sol, a MgO thin film with a high degree of crystallinity was prepared at 400 deg. C in O 2

  14. Ordered mesoporous titania/carbon hybrid monoliths for lithium-ion battery anodes with high areal and volumetric capacity.

    Science.gov (United States)

    Dörr, Tobias S; Fleischmann, Simon; Zeiger, Marco; Grobelsek, Ingrid; de Oliveira, Peter W; Presser, Volker

    2018-03-06

    Free-standing, binder-free, and conductive additive-free mesoporous titanium dioxide/carbon hybrid electrodes were prepared from co-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) block copolymer and a titanium alkoxide. By tailoring an optimized morphology, we prepared macroscopic mechanically stable 300 µm thick monoliths that were directly employed as lithium-ion battery electrodes. High areal mass loading of up to 26.4 mg/cm2 and a high bulk density of 0.88 g/cm3 were obtained. This resulted in a highly increased volumetric capacity of 155 mAh/cm3, compared to casted thin film electrodes. Further, the areal capacity of 4.5 mAh/cm2 represented a 9-fold increase compared to conventionally casted electrodes. These attractive performance metrics are related to the superior electrolyte transport and shortened diffusion lengths provided by the interconnected mesoporous nature of the monolith material, assuring superior rate handling even at high cycling rates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Structural Evolution and Stability of Sol-Gel Biocatalysts

    International Nuclear Information System (INIS)

    Rodgers, L.E.; Foster, L.J.R.; Holden, P.J.; Knott, R.B.; Bartlett, J.B.

    2005-01-01

    Full text: Immobilisation strategies for catalytic enzymes are important as they allow reuse of the biocatalysts. Sol-gel materials have been used to immobilise Candida antarctica lipase B (CALB), a commonly used industrial enzyme with a known crystal structure. The sol-gel bioencapsulate is produced through the condensation of suitable metal alkoxides in the presence of CALB, yielding materials with controlled pore sizes, volume and surface chemistry. Sol-gel matrices have been shown to prolong the catalytic life and enhance the activity of CALB, although the molecular basis for this effect has yet to be elucidated due to the limitations of analysis techniques applied to date. Small angle neutron scattering (SANS) allows such multicomponent systems to be characterised through contrast matching. In the sol-gel bioencapsulate system, at the contrast match point for silica, residual scattering intensity is due to the CALB and density fluctuations in the matrix. A SANS contrast variation series found the match point for the silica matrix, both with and without enzyme present, to be around 35 percent. The model presented here proposes a mechanism for the interaction between CALB and the surrounding sol-gel matrix, and the observed improvement in enzyme activity and matrix strength. The SANS protocol developed here may be applied more generally to bioencapsulates. (authors)

  16. Preparation of polysiloxane modified perfluorosulfonic acid composite membranes assisted by supercritical carbon dioxide for direct methanol fuel cell

    Science.gov (United States)

    Su, Lijun; Li, Lei; Li, Hong; Tang, Junkun; Zhang, Yongming; Yu, Wei; Zhou, Chixing

    Polysiloxane modified perfluorosulfonic acid (PFSA) composite membranes are prepared by using (3-mercaptopropyl) methyldimethoxysilane (MPMDMS) as a precursor of silicon alkoxide in supercritical carbon dioxide (Sc-CO 2) system. In the Sc-CO 2 system with the presence of water, Sc-CO 2 is not only used as a solvent and swelling agent, but also functioned as an acid catalyst for the condensation polymerization of MPMDMS. Characteristics of the modified composite membranes are investigated by using attenuated total reflection-infrared spectra, scanning electron microscopy and transmission electron microscopy. The modified membrane with 13.9 wt.% poly(MPMDMS) is the best one among all the modified membranes, whose methanol permeability is extremely lower and selectivity (ratio of proton conductivity to methanol permeability) is about 5.49 times higher than that of pristine membrane and 5.88 times than that of Nafion ® 117, respectively. This modified PFSA membrane still can maintain its higher selectivity value than that of Nafion ® 117 in the temperature range of 25-65 °C. Therefore, the modified membranes prepared in Sc-CO 2 system may be the suitable candidate electrolytes for direct methanol fuel cell applications.

  17. Sol-gel derived ceramic electrolyte films on porous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kueper, Timothy Walter [Univ. of California, Berkeley, CA (United States)

    1992-05-01

    A process for the deposition of sol-gel derived thin films on porous substrates has been developed; such films should be useful for solid oxide fuel cells and related applications. Yttria-stabilized zirconia films have been formed from metal alkoxide starting solutions. Dense films have been deposited on metal substrates and ceramic substrates, both dense and porous, through dip-coating and spin-coating techniques, followed by a heat treatment in air. X-ray diffraction has been used to determine the crystalline phases formed and the extent of reactions with various substrates which may be encountered in gas/gas devices. Surface coatings have been successfully applied to porous substrates through the control of substrate pore size and deposition parameters. Wetting of the substrate pores by the coating solution is discussed, and conditions are defined for which films can be deposited over the pores without filling the interiors of the pores. Shrinkage cracking was encountered in films thicker than a critical value, which depended on the sol-gel process parameters and on the substrate characteristics. Local discontinuities were also observed in films which were thinner than a critical value which depended on the substrate pore size. A theoretical discussion of cracking mechanisms is presented for both types of cracking, and the conditions necessary for successful thin formation are defined. The applicability of these film gas/gas devices is discussed.

  18. 3-D holographic lithography of organic-inorganic hybrids

    Energy Technology Data Exchange (ETDEWEB)

    Salauen, M. [LMGP, INPG, UMR 5628, 3, Parvis Louis Neel, BP 257, 38016 Grenoble Cedex (France)], E-mail: mathieu.salaun@inpg.fr; Audier, M. [LMGP, INPG, UMR 5628, 3, Parvis Louis Neel, BP 257, 38016 Grenoble Cedex (France); Delyon, F.; Duneau, M. [CPHT, Ecole Polytechnique, UMR 7644, F-91128 Palaiseau Cedex (France)

    2007-12-15

    Fabrications of ordered three-dimensional structures with submicron lattice constants were performed on organic-inorganic hybrids using a holographic lithography technique recently reported in the literature. The possibility of such a patterning has previously been demonstrated from single nanosecond laser pulse irradiation of thin films of epoxy photoresist and mixtures of methacrylate-alkoxy-silane with Zr or Ti alkoxides. In the present work, UV irradiation of similar hybrid resins were carried out through repeated laser pulses of low energy with a twofold objective: (i) to study the interference stability for future chemical gas phase decomposition experiments and (ii) to obtain patterning through large film thickness (e.g. 1 mm). The influence of several parameters on the structuration was examined from observations by scanning electron microscopy and optical diffraction. Many interdependent parameters were considered in different steps of the process, namely (i) hybrid resin preparations with required properties of stability, transparency and viscosity, (ii) film coating on different substrates, (iii) UV irradiation (energy and number of laser pulses), (iv) ultrasonic dissolution of monomer, and (v) sample drying. As results, different structuration resolutions were observed as a function of these parameters. But if the influence of a few parameters was easily understood and controlled, it has also appeared that it was not the case of all of them.

  19. 3-D holographic lithography of organic inorganic hybrids

    Science.gov (United States)

    Salaün, M.; Audier, M.; Delyon, F.; Duneau, M.

    2007-12-01

    Fabrications of ordered three-dimensional structures with submicron lattice constants were performed on organic-inorganic hybrids using a holographic lithography technique recently reported in the literature. The possibility of such a patterning has previously been demonstrated from single nanosecond laser pulse irradiation of thin films of epoxy photoresist and mixtures of methacrylate-alkoxy-silane with Zr or Ti alkoxides. In the present work, UV irradiation of similar hybrid resins were carried out through repeated laser pulses of low energy with a twofold objective: (i) to study the interference stability for future chemical gas phase decomposition experiments and (ii) to obtain patterning through large film thickness (e.g. 1 mm). The influence of several parameters on the structuration was examined from observations by scanning electron microscopy and optical diffraction. Many interdependent parameters were considered in different steps of the process, namely (i) hybrid resin preparations with required properties of stability, transparency and viscosity, (ii) film coating on different substrates, (iii) UV irradiation (energy and number of laser pulses), (iv) ultrasonic dissolution of monomer, and (v) sample drying. As results, different structuration resolutions were observed as a function of these parameters. But if the influence of a few parameters was easily understood and controlled, it has also appeared that it was not the case of all of them.

  20. Sol-gel precursors and products thereof

    Science.gov (United States)

    Warren, Scott C.; DiSalvo, Jr., Francis J.; Weisner, Ulrich B.

    2017-02-14

    The present invention provides a generalizable single-source sol-gel precursor capable of introducing a wide range of functionalities to metal oxides such as silica. The sol-gel precursor facilitates a one-molecule, one-step approach to the synthesis of metal-silica hybrids with combinations of biological, catalytic, magnetic, and optical functionalities. The single-source precursor also provides a flexible route for simultaneously incorporating functional species of many different types. The ligands employed for functionalizing the metal oxides are derived from a library of amino acids, hydroxy acids, or peptides and a silicon alkoxide, allowing many biological functionalities to be built into silica hybrids. The ligands can coordinate with a wide range of metals via a carboxylic acid, thereby allowing direct incorporation of inorganic functionalities from across the periodic table. Using the single-source precursor a wide range of functionalized nanostructures such as monolith structures, mesostructures, multiple metal gradient mesostructures and Stober-type nanoparticles can be synthesized. ##STR00001##

  1. Study of sol structure by SAXS

    International Nuclear Information System (INIS)

    Li Zhihong; Sun Jihong; Zhao Junping; Wu Dong; Sun Yuhan; Liu Yi; Sheng Wenjun; Dong Baozhong

    2000-01-01

    SiO 2 and ZrO 2 sols were prepared by base-catalyzed hydrolysis and condensation of alkoxides in alcohol. PEG and diglycol were used as organic modifiers of SiO 2 and ZrO 2 sols respectively. The structure evolution during the sol-gel process was investigated by small angle X-ray scattering (SAXS) with synchrotron radiation as X-ray source. SAXS results show that the silica and zirconic sols are poly-dispersed, i.e., with proper size distribution. SAXS results also show that silica and zirconic aggregates are mass fractals, fractal dimensions span the regime 0.23-2.56 corresponding to very sparse and more branched and compact structures. The formation of a mass fractal is a kind of nonlinear process. Both RLCA and Eden models dominate the kinetic growth under base-catalyzed condition. It is also shown that the SAXS profiles do not agree with Porod's law and have negative or positive slopes, suggesting that the dispersive interfacial layer exists between sol particle and dispersing agent. The thickness of the interfacial layer falls between approximately 1.00 and 22.00 nm for samples prepared under various conditions. Both agreement with and deviation from Porod's law in SAXS are summarized, especially proposing the analysis method upon positive deviation with slit-smeared SAXS data

  2. Masked N-Heterocyclic Carbene-Catalyzed Alkylation of Phenols with Organic Carbonates.

    Science.gov (United States)

    Lui, Matthew Y; Yuen, Alexander K L; Masters, Anthony F; Maschmeyer, Thomas

    2016-09-08

    An easily prepared masked N-heterocyclic carbene, 1,3-dimethylimidazolium-2-carboxylate (DMI-CO2 ), was investigated as a "green" and inexpensive organocatalyst for the alkylation of phenols. The process made use of various low-toxicity and renewable alkylating agents, such as dimethyl- and diethyl carbonate, in a focused microwave reactor. DMI-CO2 was found to be a very active catalyst and excellent yields of a range of aryl alkyl ethers were obtained under relatively benign conditions. The observed difference in the conversion behavior of phenol methylation, in the presence of either the carbene or 1,8-diazabicycloundec-7-ene (DBU) catalyst, was rationalized on the basis of mechanistic investigations. The primary mode of action for the N-heterocyclic carbene is nucleophilic catalysis. Activation of the dialkyl carbonate electrophile results in concomitant evolution of an organo-soluble alkoxide, which deprotonates the phenolic starting material. In contrast, DBU is initially protonated by the phenol and thus consumed. Subsequent regeneration and participation in nucleophilic catalysis only becomes significant after some phenolate alkylation occurs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Microemulsion mediated synthesis of BaTiO3 – Ag nanocomposites

    Directory of Open Access Journals (Sweden)

    Songhak Yoon

    2009-06-01

    Full Text Available BaTiO3 – Ag composite nanopowders were synthesized via microemulsion mediated synthesis through the hydrolytic decomposition of mixed metal alkoxide solutions as precursor for the BaTiO3 and the reduction of silver nitrate in the presence of polyvinylpyrrolidone (PVP as source for the Ag nanoparticles. The X-ray diffraction (XRD patterns indicate that BaTiO3 and Ag phases were successfully synthesized in the composite powders. Scanning electron microscopy (SEM and transmission electron microscopy (TEM show that the synthesized BaTiO3 nanoparticles were aggregates of nanosized primary particles as small as 10 nm in diameter and the average particle size of nanocrystalline Ag was about 100 nm. Calcination and sintering studies reveal that there exists a difference in the sintering behaviour of BaTiO3 and Ag in the composite nanopowders. Thermogravimetric analysis (TGA shows weight losses due to the burnout of organic residues arising from the synthesis, the release of water from the surface and separation of hydroxyl ions from the lattice of BaTiO3 nanoparticles. A dilatometric study of BaTiO3-Ag composite confi rmed a strong difference in the shrinkage behaviour compared to that of the pure BaTiO3 obtained by microemulsion mediated synthesis.

  4. Survey report for fiscal 1998. Joint research project with researchers related to petroleum substituting energies in the EU countries; 1998 nendo EU shokoku no sekiyu daitai energy kanren kenkyusha tono kyodo kenkyu jigyo chosa hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    It was intended to invite researchers related to petroleum substituting energies from the EU countries to perform joint researches at research organizations under the auspices of the Agency of Industrial Science and Technology having deep relations with research themes of the invited researchers, to deepen the mutual understanding, and to form efficient cooperative relationship. The intention is also to contribute to research and development of petroleum substituting energies to be used in Japan in the future. The research themes, researchers, their research organizations, and the receiving research organizations are as follows: (1) evaluation of reservoir impedance in high-temperature rock experimental fields by Mr. Ralph Weidler (Germany) at Ruhr University received by the Resource and Environmental Technology Research Institute; (2) changing the particle boundary structure of ceramics by using the alkoxide process by Dr. Ramon Torrecillas (Spain) at Institute Nacional del Carbon received by the Nagoya Industrial Technology Research Institute; (3) research on corrosion in metallic materials for molten carbonate type fuel cells by Dr. Giuseppe Calogero (Italy) at Institute for Transformation and Storage of Energy received by the Osaka Industrial Technology Research Institute; and (4) estimation of behavior of deep geothermal reservoirs with high enthalpy by Dr. Enrico Maranini at Universita' Di Ferrara received by the Geology Survey Center. (NEDO)

  5. Manganite perovskite ceramics, their precursors and methods for forming

    Science.gov (United States)

    Payne, David Alan; Clothier, Brent Allen

    2015-03-10

    Disclosed are a variety of ceramics having the formula Ln.sub.1-xM.sub.xMnO.sub.3, where 0.Itoreq.x.Itoreq.1 and where Ln is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; M is Ca, Sr, Ba, Cd, or Pb; manganite precursors for preparing the ceramics; a method for preparing the precursors; and a method for transforming the precursors into uniform, defect-free ceramics having magnetoresistance properties. The manganite precursors contain a sol and are derived from the metal alkoxides: Ln(OR).sub.3, M(OR).sub.2 and Mn(OR).sub.2, where R is C.sub.2 to C.sub.6 alkyl or C.sub.3 to C.sub.9 alkoxyalkyl, or C.sub.6 to C.sub.9 aryl. The preferred ceramics are films prepared by a spin coating method and are particularly suited for incorporation into a device such as an integrated circuit device.

  6. Decorating poly(alkyl aryl-ether) dendrimers with metallacarboranes.

    Science.gov (United States)

    Núñez, Rosario; Juárez-Pérez, Emilio José; Teixidor, Francesc; Santillan, Rosa; Farfán, Norberto; Abreu, Arturo; Yépez, Rebeca; Viñas, Clara

    2010-11-01

    A new family of polyanionic poly(alkyl aryl-ether) metallodendrimers decorated with four and eight cobaltabisdicarbollide units have been obtained in high yield by the ring-opening reaction of cyclic oxonium [3,3'-Co(8-(C(2)H(4)O)(2)-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))] with alkoxides formed by deprotonation of terminal alcohols in the α,α'-bis[3,5-bis(hydroxymehyl)phenoxy]-p-xylene, α,α'-bis[3,5-bis(hydroxymehyl)phenoxy]-m-xylene, α,α'-bis[3,5-bis-[3,5-bis(hydroxymethyl)phenoxy]methylen]phenoxy]-p-xylene, and α,α,'-bis[3,5-bis-[3,5-bis(hydroxymethyl)phenoxy]methylen]phenoxy]-m-xylene dendrimers. The crystal structure of the precursor α,α'-bis[3,5-bis(chloromethyl)phenoxy]-p-xylene is also described. Final products are fully characterized by FTIR, NMR, UV-vis spectroscopies and elemental analysis. For metallodendrimers, the UV-vis absorptions have been a good tool for estimating the experimental number of cobaltabisdicarbollide units peripherally attached to the dendrimeric structure and consequently to corroborate the complete functionalization of the dendrimers.

  7. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING; FINAL

    International Nuclear Information System (INIS)

    LICHTENBERGER, DENNIS L.

    2002-01-01

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems

  8. Phase formation of V2O5.xNb2O5 compounds via gels and freeze-dried precursors

    International Nuclear Information System (INIS)

    Langbein, Hubert; Mayer-Uhma, Tobias

    2009-01-01

    An X-ray powder diffraction study of the phase formation in the system V 2 O 5 /Nb 2 O 5 is performed. Freeze-dried ammonium vanadate and ammonium oxalato niobate, alkoxide-derived xerogels and a mixture of active oxides are used as precursors to compare the resulting phase composition. Thermal decomposition of the freeze-dried precursor is monitored with DTA/TG and mass spectrometry. In the quasi-binary system V 2 O 5 -Nb 2 O 5 metastable VNbO 5 , V 4 Nb 18 O 55 , VNb 9 O 25 and solid solutions of V 2 O 5 in TT-Nb 2 O 5 as also thermodynamically stable VNb 9 O 25 exist. The thermal decomposition of freeze-dried vanadate-oxalatoniobate solution allows the synthesis of all these phases in a relative simple manner. Structural relationships between an intermediate phase and the product, or, in the case of solid-state reactions, between one of the starting oxide and the product, favour the desired reaction. Therefore, the structure of a former phase influences or directs the structure of the product similar to a topotactic reaction

  9. Achievement report for fiscal 1998. Research and development on a new manufacturing method for functional thin films suitable for recycling, and their application to colored glasses (the second year); 1998 nendo seika hokokusho. Recycle ni tekishita kinosei usumaku no shinki seizoho to chakushoku glass eno oyo ni kansuru kenkyu kaihatsu (dai 2 nendo)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    A new thin film manufacturing method is established to add a function to glass material surface, as a new material technology which harmonizes with global environment, and is suitable for resource re-utilization and energy conservation. It is intended to develop a leading technology to promote recycling of colored glasses by applying this technical method to colored glasses. Fiscal 1998 has implemented subsequently to fiscal 1997 the following subjects in the three research items composed of a new manufacturing method of functional thin films, application of the functional thin films to colored glasses, and the comprehensive investigative studies: establishment of an industrial manufacturing method for color coating liquid and evaluation of basic characteristics of the colored functional thin films, optimization of element technology for photo-sensitive gel films by means of chemically modifying metallic alkoxide, tests of forming films on glass bottles and plate glasses by using a coating machine installed in fiscal 1997, design and prototype fabrication of a new demonstration coating machine, and analysis on thermal decomposition of the colored thin films. Optimization was performed on the element technology for manufacturing sol-gel functional thin films, and a survey was carried out on recycling systems of colored glasses adopted in Europe. (NEDO)

  10. Insertion, reduction, and carbon-carbon coupling induced by monomeric aluminum hydride compounds bearing substituted pyrrolyl ligands.

    Science.gov (United States)

    Lin, Che-Yu; Tsai, Chia-Fu; Chen, Hsing-Jen; Hung, Chen-Hsiung; Yu, Ru-Ching; Kuo, Pei-Cheng; Lee, Hon Man; Huang, Jui-Hsien

    2006-04-03

    A monomeric aluminum hydride complex bearing substituted pyrrolyl ligands, AlH[C(4)H(3)N(CH(2)NMe(2))-2](2) (1), was synthesized and structurally characterized. To further confirm the presence of Al--H bonds, the compound AlD[C(4)H(3)N(CH(2)NMe(2))-2](2) ([D]1) was synthesized by reacting LiAlD(4) with [C(4)H(4)N(CH(2)NMe(2))-2]. Compound 1 and [D]1 react with phenyl isothiocyanate yielding Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCHNPh] (2) and Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCDNPh] ([D]2) by insertion. The reactions of 1 with 9-fluorenone and benzophenone generated the unusual aluminum alkoxide complexes 3 and 4, respectively, through intramolecular proton abstraction and C-C coupling. A mechanistic study shows that 9-fluorenone coordinates to [D]1 and releases one equivalent of HD followed by C-C coupling and hydride transfer to yield the final product. Reduction of benzil with 1 affords aluminum enediolate complex 5 in moderate yield. Mechanistic studies also showed that the benzil was inserted into the aluminum hydride bond of [D]1 through hydroalumination followed by proton transfer to generate the final product [D]5. All new complexes have been characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography.

  11. Quantum dot based on tin/titanium mixed oxide doped with europium synthesized by protein sol-gel method

    International Nuclear Information System (INIS)

    Paganini, Paula P.; Felinto, Maria Claudia F.C.; Brito, Hermi F.

    2011-01-01

    Special luminescence biomarkers have been developed to find more sensitive fluoroimmunoassay methods. A new generation of these biomarkers is the semiconductors nanocrystals, known as quantum dots, doped with lanthanides. The use of lanthanides ions as luminescent markers has many advantages, for example a security method, low cost, high specificity and also the luminescence can be promptly measured with high sensibility and accuracy. The protein sol-gel is a modification of conventional method, in which the coconut water replacing the alkoxides normally used. The advantage is that, the proteins present in coconut water bind chemically with metal salts forming a polymer chain. This work presents nanoparticles based on tin/titanium mixed oxide doped with 3% of europium synthesized by protein sol-gel method. The nanoparticles were burned at 300 deg C, 500 deg C, 800 deg C and 1100 deg C. The samples were analyzed and characterized by thermal analysis, X-ray powder diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The synthesis was effective and the nanoparticles showed nanometric size and structural differences with the annealing. To be used in the fluoroimmunoassays tests, these particles need to be functionalized before be connect with biological molecules and after this process, these nanoparticles going to be submitted at gamma radiation for sterilization. (author)

  12. Three dimensional mesoporous silica strucutres with templated macropores

    Science.gov (United States)

    Kothari, Rohit; Hendricks, Nicholas R.; Watkins, James J.

    2013-03-01

    A novel approach to fabricate three dimensional macroporous structures comprised of mesoporous silica is demonstrated. Well-ordered mesoporous silica structures with macroporosity were obtained by using humidified supercritical carbon dioxide as a carrier medium to infuse and domain selectively condense silica alkoxide precursor in a microphase separated block copolymer/small molecule additive blend solution casted on macroporous supports such as cellulose filter paper and sponge. Subsequent calcination was used to remove both the block copolymer template and the macroporous support. Transition electron microscopy (TEM) and small angle x-ray diffraction (SAXD) confirmed the presence of well-ordered mesopores. Scanning electron microscopy confirmed faithful replication of the features of the macroporous supports. Physisorption showed BET surface areas as high as 400m2/g and the BJH pore size distributions obtained are in close agreement with the TEM and SAXD results. This dual scale porosity within the silica template will enhance overall transport and diffusion, which is appropriate for many applications including catalysis and sensing.

  13. Photocatalytic activity and RNO dye degradation of nitrogen-doped TiO{sub 2} prepared by ionothermal synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Pipi, Angelo; Ruotolo, Luis, E-mail: pluis@ufscar.br [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Engenharia Quimica; Byzynski, Gabriela [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil)

    2017-05-15

    This work concerns the preparation a nitrogen-doped TiO{sub 2} by ionothermal synthesis methods and the photocatalytic studies. In this procedure, alkoxide was used as a titanium source, and a deep eutectic mixture of choline chloride and urea (molar ratio 1:2) served as a solvent and source of nitrogen. Different samples were synthesized varying the percentages of the eutectic mixture, titanium butoxide, and water, as well as temperature and reaction time. The catalysts were characterized by X-ray diffraction, Raman spectrometry, scanning electron microscopy, and diffuse reflectance spectroscopy. N-doping was confirmed by X-ray photoelectron spectroscopy. The photocatalytic activity of the N-TiO{sub 2} nanoparticles was evaluated in the oxidation of N,N-dimethyl-4-nitrosoaniline (RNO) dye. The best photocatalytic activity under illumination by UV and visible light was found for the catalysts prepared under reflux in the presence of water, and for the catalysts prepared hydrothermally using intermediate percentages of the nitrogen source (the eutectic mixture). (author)

  14. Microstructure evolution, thermal stability and fractal behavior of water vapor flow assisted in situ growth poly(vinylcarbazole)-titania quantum dots nanocomposites

    Science.gov (United States)

    Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Mombrú, Alvaro W.

    2017-12-01

    Here, we report a novel strategy for the preparation of TiO2 quantum dots fillers prepared from alkoxide precursor via in situ water vapor flow diffusion into poly(N-vinylcarbazole) host. A detailed characterization by means of infrared and Raman spectroscopy, X-ray powder diffraction, small angle X-ray scattering and differential scanning calorimetry is reported. The growth mechanism of both crystallites and particles was mostly governed by the classical coarsening reaction limited growth and the polymer host showed no detectable chemical modifications at the interface or active participation in the growing process. The main relevance of our strategy respect to the typical sol-gel growth in solution is the possibility of the interruption of the reaction by simple stopping the water vapor flow diffusion into the polymer host thus achieving good control in the nanoparticles size. The thermal stability and fractal behavior of our nanocomposites were also studied by differential scanning calorimetry and in situ small angle X-ray scattering versus temperature. Strong correlations between modifications in the fractal behavior and glass transition or fusion processes were observed for these nanocomposites.

  15. Titanium dioxide nanoparticles: synthesis, X-Ray line analysis and chemical composition study

    Energy Technology Data Exchange (ETDEWEB)

    Chenari, Hossein Mahmoudi, E-mail: mahmoudi_hossein@guilan.ac.ir, E-mail: h.mahmoudiph@gmail.com [University of Guilan, Rasht (Iran, Islamic Republic of); Seibel, Christoph; Hauschild, Dirk; Reinert, Friedrich [Karlsruhe Institute of Technology - KIT, Gemeinschaftslabor für Nanoanalytik, Karlsruhe (Germany); Abdollahian, Hossein [Nanotechnology Research Center of Urmia University, Urmia, (Iran, Islamic Republic of)

    2016-11-15

    TiO{sub 2} nanoparticles have been synthesized by the sol-gel method using titanium alkoxide and isopropanol as a precursor. The structural properties and chemical composition of the TiO{sub 2} nanoparticles were studied using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy.The X-ray powder diffraction pattern confirms that the particles are mainly composed of the anatase phase with the preferential orientation along [101] direction. The physical parameters such as strain, stress and energy density were investigated from the Williamson- Hall (W-H) plot assuming a uniform deformation model (UDM), and uniform deformation energy density model (UDEDM). The W-H analysis shows an anisotropic nature of the strain in nano powders. The scanning electron microscopy image shows clear TiO{sub 2} nanoparticles with particle sizes varying from 60 to 80nm. The results of mean particle size of TiO{sub 2} nanoparticles show an inter correlation with the W-H analysis and SEM results. Our X-ray photoelectron spectroscopy spectra show that nearly a complete amount of titanium has reacted to TiO{sub 2}. (author)

  16. Stabilization/Solidification of radioactive molten salt waste via gel-route pretreatment.

    Science.gov (United States)

    Park, Hwan-Seo; Kim, In-Tae; Kim, Hwan-Young; Ryu, Seung-Kon; Kim, Joon-Hyung

    2007-02-15

    The volatilization of radionuclides during the stabilization/solidification of radioactive wastes at high temperatures is one of the major problems to be considered in choosing suitable wasteforms, process, material systems, etc. This paper reports a novel method to convert volatile wastes into nonvolatile compounds via a sol-gel process, which is different from the conventional method using metal-alkoxides and organic solvents. The material system was designed with sodium silicate (Si) as a gelling agent, phosphoric acid (P) as a catalyst/stabilizer, aluminum nitrate (Al) as a property promoter, and H20 as a solvent. A novel structural model for the chemical conversion of molten salt waste, named RPRM (Reaction Product in Reaction Module), was established, and the waste could be solidified with glass matrix via a simple procedure. The leached fraction of Cs and Sr by a PCT leaching method was 0.72% and 0.014%, respectively. In conclusion, the RPRM model isto converttargetwastes into stable and manageable products, not to obtain a specific crystalline product for each radionuclide. This paper suggested a new stabilization/solidification method for salt wastes by establishing the gel-forming material system and showing a practical example, not a new synthesis method of stable crystalline phase. This process, named "gel-route stabilization/solidification (GRSS)", will be a prospective alternative with stable chemical process on the immobilization of salt wastes and various mixed radioactive waste for final disposal.

  17. Molecular and Silica-Supported Molybdenum Alkyne Metathesis Catalysts: Influence of Electronics and Dynamics on Activity Revealed by Kinetics, Solid-State NMR, and Chemical Shift Analysis.

    Science.gov (United States)

    Estes, Deven P; Gordon, Christopher P; Fedorov, Alexey; Liao, Wei-Chih; Ehrhorn, Henrike; Bittner, Celine; Zier, Manuel Luca; Bockfeld, Dirk; Chan, Ka Wing; Eisenstein, Odile; Raynaud, Christophe; Tamm, Matthias; Copéret, Christophe

    2017-12-06

    Molybdenum-based molecular alkylidyne complexes of the type [MesC≡Mo{OC(CH 3 ) 3-x (CF 3 ) x } 3 ] (MoF 0 , x = 0; MoF 3 , x = 1; MoF 6 , x = 2; MoF 9 , x = 3; Mes = 2,4,6-trimethylphenyl) and their silica-supported analogues are prepared and characterized at the molecular level, in particular by solid-state NMR, and their alkyne metathesis catalytic activity is evaluated. The 13 C NMR chemical shift of the alkylidyne carbon increases with increasing number of fluorine atoms on the alkoxide ligands for both molecular and supported catalysts but with more shielded values for the supported complexes. The activity of these catalysts increases in the order MoF 0 catalysts coupled with DFT/ZORA calculations rationalize the NMR spectroscopic signatures and discernible activity trends at the frontier orbital level: (1) increasing the number of fluorine atoms lowers the energy of the π*(M≡C) orbital, explaining the more deshielded chemical shift values; it also leads to an increased electrophilicity and higher reactivity for catalysts up to MoF 6 , prior to a sharp decrease in reactivity for MoF 9 due to the formation of stable metallacyclobutadiene intermediates; (2) the silica-supported catalysts are less active than their molecular analogues because they are less electrophilic and dynamic, as revealed by their 13 C NMR chemical shift tensors.

  18. Synthesis of Barium Titanate Using Deep Eutectic Solvents.

    Science.gov (United States)

    Boston, Rebecca; Foeller, Philip Y; Sinclair, Derek C; Reaney, Ian M

    2017-01-03

    Novel synthetic routes to prepare functional oxides at lower temperatures are an increasingly important area of research. Many of these synthetic routes, however, use water as the solvent and rely on dissolution of the precursors, precluding their use with, for example, titanates. Here we present a low-cost solvent system as a means to rapidly create phase-pure ferroelectric barium titanate using a choline chloride-malonic acid deep eutectic solvent. This solvent is compatible with alkoxide precursors and allows for the rapid synthesis of nanoscale barium titanate powders at 950 °C. The phase and morphology were determined, along with investigation of the synthetic pathway, with the reaction proceeding via BaCl 2 and TiO 2 intermediates. The powders were also used to create sintered ceramics, which exhibit a permittivity maximum corresponding to a tetragonal-cubic transition at 112 °C, as opposed to the more conventional temperature of ∼120 °C. The lower-than-expected value for the ferro- to para-electric phase transition is likely due to undetectable levels of contaminants.

  19. Solution Synthesis and Processing of PZT Materials for Neutron Generator Applications

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, M.A.; Ewsuk, K.G.; Montoya, T.V.; Moore, R.H.; Sipola, D.L.; Tuttle, B.A.; Voigt, J.A.

    1998-12-01

    A new solution synthesis route has been developed for the preparation of lead-based ferroelectric materials (patent filed). The process produces controlled stoichiometry precursor powders by non-aqueous precipitation. For a given ferroelectric material to be prepared, a metal acetate/alkoxide solution containing constituent metal species in the appropriate ratio is mixed with an oxalic acid/n-propanol precipitant solution. An oxalate coprecipitate is instantly fonned upon mixing that quantitatively removes the metals from solution. Most of the process development was focused on the synthesis and processing of niobium-substituted lead zirconate titanate with a Zr-to-Ti ratio of 95:5 (PNZT 95/5) that has an application in neutron generator power supplies. The process was scaled to produce 1.6 kg of the PNZT 95/5 powder using either a sen-ii-batch or a continuous precipitation scheme. Several of the PNZT 95/5 powder lots were processed into ceramic slug form. The slugs in turn were processed into components and characterized. The physical properties and electrical performance (including explosive functional testing of the components met the requirements set for the neutron generator application. Also, it has been demonstrated that the process is highly reproducible with respect to the properties of the powders it produces and the properties of the ceramics prepared from its powders. The work described in this report was funded by Sandia's Laboratory Directed Research and Development Program.

  20. Reactive Precipitation of Anhydrous Alkali Sulfide Nanocrystals with Concomitant Abatement of Hydrogen Sulfide and Cogeneration of Hydrogen.

    Science.gov (United States)

    Li, Xuemin; Zhao, Yangzhi; Brennan, Alice; McCeig, Miranda; Wolden, Colin A; Yang, Yongan

    2017-07-21

    Anhydrous alkali sulfide (M 2 S, M=Li or Na) nanocrystals (NCs) are important materials central to the development of next generation cathodes and solid-state electrolytes for advanced batteries, but not commercially available at present. This work reports an innovative method to directly synthesize M 2 S NCs through alcohol-mediated reactions between alkali metals and hydrogen sulfide (H 2 S). In the first step, the alkali metal is complexed with alcohol in solution, forming metal alkoxide (ROM) and releasing hydrogen (H 2 ). Next, H 2 S is bubbled through the ROM solution, where both chemicals are completely consumed to produce phase-pure M 2 S NC precipitates and regenerate alcohol that can be recycled. The M 2 S NCs morphology may be tuned through the choice of the alcohol and solvent. Both synthetic steps are thermodynamically favorable (ΔG m o <-100 kJ mol -1 ), proceeding rapidly to completion at ambient temperature with almost 100 % atom efficiency. The net result, H 2 S+2 m→M 2 S+H 2 , makes good use of a hazardous chemical (H 2 S) and delivers two value-added products that naturally phase separate for easy recovery. This scalable approach provides an energy-efficient and environmentally benign solution to the production of nanostructured materials required in emerging battery technologies. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Sol-gel preparation of Ag-silica nanocomposite with high electrical conductivity

    Science.gov (United States)

    Ma, Zhijun; Jiang, Yuwei; Xiao, Huisi; Jiang, Bofan; Zhang, Hao; Peng, Mingying; Dong, Guoping; Yu, Xiang; Yang, Jian

    2018-04-01

    Sol-gel derived noble-metal-silica nanocomposites are very useful in many applications. Due to relatively low price, higher conductivity, and higher chemical stability of silver (Ag) compared with copper (Cu), Ag-silica has gained much more research interest. However, it remains a significant challenge to realize high loading of Ag content in sol-gel Ag-silica composite with high structural controllability and nanoparticles' dispersity. Different from previous works by using multifunctional silicon alkoxide to anchor metal ions, here we report the synthesis of Ag-silica nanocomposite with high loading of Ag nanoparticles by employing acetonitrile bi-functionally as solvent and metal ions stabilizer. The electrical conductivity of the Ag-silica nanocomposite reached higher than 6800 S/cm. In addition, the Ag-silica nanocomposite could simultaneously possess high electrical conductivity and positive conductivity-temperature coefficient by properly controlling the loading content of Ag. Such behavior is potentially advantageous for high-temperature devices (like phosphoric acid fuel cells) and inhibiting the thermal-induced increase of devices' internal resistance. The strategy proposed here is also compatible with block-copolymer directed self-assembly of mesoporous material, spin-coating of film and electrospinning of nanofiber, making it more charming in various practical applications.

  2. Silicatein Filaments and Subunits from a Marine Sponge Direct the Polymerization of Silica and Silicones in vitro

    Science.gov (United States)

    Cha, Jennifer N.; Shimizu, Katsuhiko; Zhou, Yan; Christiansen, Sean C.; Chmelka, Bradley F.; Stucky, Galen D.; Morse, Daniel E.

    1999-01-01

    Nanoscale control of the polymerization of silicon and oxygen determines the structures and properties of a wide range of siloxane-based materials, including glasses, ceramics, mesoporous molecular sieves and catalysts, elastomers, resins, insulators, optical coatings, and photoluminescent polymers. In contrast to anthropogenic and geological syntheses of these materials that require extremes of temperature, pressure, or pH, living systems produce a remarkable diversity of nanostructured silicates at ambient temperatures and pressures and at near-neutral pH. We show here that the protein filaments and their constituent subunits comprising the axial cores of silica spicules in a marine sponge chemically and spatially direct the polymerization of silica and silicone polymer networks from the corresponding alkoxide substrates in vitro, under conditions in which such syntheses otherwise require either an acid or base catalyst. Homology of the principal protein to the well known enzyme cathepsin L points to a possible reaction mechanism that is supported by recent site-directed mutagenesis experiments. The catalytic activity of the "silicatein" (silica protein) molecule suggests new routes to the synthesis of silicon-based materials.

  3. Rationalization of the pKa values of alcohols and thiols using atomic charge descriptors and its application to the prediction of amino acid pKa's

    DEFF Research Database (Denmark)

    Ugur, Ilke; Marion, Antoine; Parant, Stéphane

    2014-01-01

    In a first step toward the development of an efficient and accurate protocol to estimate amino acids' pKa's in proteins, we present in this work how to reproduce the pKa's of alcohol and thiol based residues (namely tyrosine, serine, and cysteine) in aqueous solution from the knowledge...... of the experimental pKa's of phenols, alcohols, and thiols. Our protocol is based on the linear relationship between computed atomic charges of the anionic form of the molecules (being either phenolates, alkoxides, or thiolates) and their respective experimental pKa values. It is tested with different environment......) to also predict pKa's of thiols, phenols, and alcohols is analyzed. From our benchmarks, the best combination to reproduce experimental pKa's is to compute NPA atomic charge using the CPCM model at the B3LYP/3-21G and M062X/6-311G levels for alcohols (R(2) = 0.995) and thiols (R(2) = 0.986), respectively...

  4. Water concentration controlled hydrolysis and crystallization in n-octanol to TiO{sub 2} nanocrystals with size below 10 nm

    Energy Technology Data Exchange (ETDEWEB)

    Wang Meilan [School of Chemical and Biological Science and Engineering, Yantai University, Yantai 264005 (China); He Tao, E-mail: htzy79@yahoo.com.cn [School of Chemical and Biological Science and Engineering, Yantai University, Yantai 264005 (China); Pan Yanfei; Liao Weiping [School of Chemical and Biological Science and Engineering, Yantai University, Yantai 264005 (China); Zhang Shangzhou; Du Wei [School of Environment and Materials Engineering, Yantai University, Yantai 264005 (China)

    2011-11-01

    Highlights: {yields} Controlled hydrolysis of alkoxide was realized by adjusting water concentration. {yields} Carrying out hydrolysis under different water concentration gave hydrolyzed intermediate with different composition. {yields} A precise size control below 10 nm for anatase TiO{sub 2} nanocrystals was realized. - Abstract: Hydrolysis of tetrabutyl titanate (TBT) and crystallization from hydrolyzed intermediates were carried out in a simple ternary system including n-octanol, TBT and water. Anatase TiO{sub 2} nanocrystals (NCS) were prepared with precise size control below 10 nm. The hydrolysis rate at different water concentration (C{sub water}) was evaluated by measuring the induction time before turbidity changing of the synthetic solution. Fourier transform infrared spectrum (FT-IR) and thermogravimetric/differential thermal analysis (TG/DTA) techniques were applied to make clear the composition of hydrolyzed intermediates obtained at different C{sub water}. Powder X-ray diffraction (XRD) technique was used to track the crystallization process of TiO{sub 2} NCS. Transmission electron microscopy (TEM), XRD, FT-IR and TG/DTA techniques were used to characterize the particular properties of NCS. The C{sub water} controlled mechanism responsible for the slow hydrolysis and crystallization were discussed. Since no other organic capping ligands or rapid injecting techniques were used to limit NCS' growth and the solvent n-octanol can be easily separated and reused, this simple synthetic process is of green chemistry and has application potential in large-scale preparation of inorganic NCS.

  5. Thermoluminescent dosimetry of beta radiations of {sup 90} Sr/ {sup 90} Y using amorphous ZrO{sub 2}; Dosimetria termoluminiscente de radiaciones beta de {sup 90} Sr/ {sup 90} Y usando ZrO{sub 2} amorfo

    Energy Technology Data Exchange (ETDEWEB)

    Rivera M, T. [CICATA-Legaria, IPN, Legaria Num. 694, 11500 Mexico D.F. (Mexico); Olvera T, L.; Azorin N, J.; Barrera R, M.; Soto E, A.M. [UAM-I, 09340 Mexico D.F. (Mexico)

    2005-07-01

    In this work the results of studying the thermoluminescent properties (Tl) of the zirconium oxide in its amorphous state (ZrO{sub 2}-a) before beta radiations of {sup 90} Sr/ {sup 90} Y are presented. The amorphous powders of the zirconium oxide were synthesized by means of the sol-gel technique. The sol-gel process using alkoxides like precursors, is an efficient method to prepare a matrix of zirconium oxide by hydrolysis - condensation of the precursor to form chains of Zr-H{sub 3} and Zr-O{sub 2}. One of the advantages of this technique is the obtention of gels at low temperatures with very high purity and homogeneity. The powders were characterized by means of thermal analysis and by X-ray diffraction. The powders of ZrO{sub 2}-a, previously irradiated with beta particles of {sup 90} Sr/{sup 90} Y, presented a thermoluminescent curve with two peaks at 150 and 257 C. The dissipation of the information of the one ZrO{sub 2}-a was of 40% the first 2 hours remaining constant the information for the following 30 days. The reproducibility of the information was of {+-} 2.5% in standard deviation. The studied characteristics allow to propose to the amorphous zirconium oxide as thermoluminescent dosemeter for the detection of beta radiation. (Author)

  6. Synthesis of amorphous zirconium oxide with luminescent characteristics; Sintesis de oxido de circonio amorfo con caracteristicas luminiscentes

    Energy Technology Data Exchange (ETDEWEB)

    Barrera S, M.; Chavez G, M.; Soto E, A.M.; Velasquez O, C.; Garcia S, M.A.; Olvera T, L.; Rivera M, T. [UAM-I, 09340 Mexico D.F. (Mexico)

    2004-07-01

    It was prepared zirconium oxide, ZrO{sub 2}, by means of hydrolysis-condensation reactions (sol-gel method), using zirconium propoxide, Zr(C{sub 3}H{sub 7}O){sub 4}, as precursor and nitric acid, HNO{sub 3}, as catalyst of the hydrolysis reaction. In this synthesis it was used a molar ratio water-alkoxide, r=n{sub H2O}/n{sub Zr}(C{sub 3}H{sub 7}0){sub 4}, high, similar to 200, so that the hydrolysis happens quickly and the nucleation and growth are completed in very little time. The solid was characterized with Ftir spectrophotometry, Differential thermal analysis (Dta), Thermal gravimetric analysis (T G), X-ray diffraction of powders, Scanning electron microscopy (Sem) and X-ray Dispersion energy (EDX). The ZrO{sub 2} obtained by this way is amorphous even to 300 C and it consists of big aggregates. The amorphous ZrO{sub 2}, presents thermoluminescent behavior, after it was irradiated with UV radiation and beta particles of {sup 90}Sr/{sup 90}Y and it was thermally stimulated. (Author)

  7. Comparison of the Biological Properties of Several Marine Sponge-Derived Sesquiterpenoid Quinones

    Directory of Open Access Journals (Sweden)

    Ping Yin

    2007-07-01

    Full Text Available Eight naturally occurring marine-sponge derived sesquiterpenoid quinones wereevaluated as potential inhibitors of pyruvate phosphate dikinase (PPDK, a C4 plantregulatory enzyme. Of these, the hydroxyquinones ilimaquinone, ethylsmenoquinone andsmenoquinone inhibited PPDK activity with IC50’s (reported with 95% confidenceintervals of 285.4 (256.4 – 317.7, 316.2 (279.2 – 358.1 and 556.0 (505.9 – 611.0 μM,respectively, as well as being phytotoxic to the C4 plant Digitaria ciliaris. The potentialanti-inflammatory activity of these compounds, using bee venom phospholipase A2(PLA2, was also evaluated. Ethylsmenoquinone, smenospongiarine, smenospongidine andilimaquinone inhibited PLA2 activity (% inhibition of 73.2 + 4.8 at 269 μM, 61.5 + 6.1 at242 μM, 41.0 + 0.6 at 224 μM and 36.4 + 8.2 at 279 μM, respectively. SAR analysesindicate that a hydroxyquinone functionality and a short, hydroxide/alkoxide side-chain atC-20 is preferred for inhibition of PPDK activity, and that a larger amine side-chain at C-20 is tolerated for PLA2 inhibitory activity.

  8. Radiosynthesis of [F-18]fluoxetine as a potential radiotracer for serotonin reuptake sites

    Energy Technology Data Exchange (ETDEWEB)

    Das, M.K.; Mukherjee, Jogeshwar (Chicago Univ., IL (United States). Dept. of Radiology)

    1993-05-01

    Synthesis of 4-nitro-[alpha]-bromo-[alpha],[alpha]-difluorotoluene was accomplished in two steps starting from 4-nitrobenzaldehyde, with a 30% overall yield. Radiolabeling of 4-nitro-[alpha]-bromo-[alpha], [alpha]-difluorotoluene with no-carrier-added [[sup 18]F]fluoride provided 4-nitro-[alpha],[alpha]-difluoro-[alpha]-[[sup 18]F] fluorotoluene in 2-4% yields with a specific activity of 2590 GBq/mmol (70 Ci/mmol). The effect of the reaction temperature on the radiochemical yield and specific activity of the radiolabeling reaction was studied. Radiochemical yields increased, whereas specific activity decreased, with increasing temperature. Radiosynthesis of [[sup 18]F] fluoxetine involved coupling of 4-nitro-[alpha],[alpha]-difluoro-[alpha]-[[sup 18]F]fluorotoluene with the sodium alkoxide of (S)-3-(methylamino)-1-phenyl-1-propanol. The overall yield of HPLC purified [[sup 18]F]fluoxetine was 1-2% (decay-corrected; total radiosynthesis time, 150-180 min). The specific activity of the product was 1480 GBq/mmol (40 Ci/mmol). (Author).

  9. Fabrication of TiO2 Nanotanks Embedded in a Nanoporous Alumina Template

    Directory of Open Access Journals (Sweden)

    C. Massard

    2015-01-01

    Full Text Available The feasibility of surface nanopatterning with TiO2 nanotanks embedded in a nanoporous alumina template was investigated. Self-assembled anodized aluminium oxide (AAO template, in conjunction with sol gel process, was used to fabricate this nanocomposite object. Through hydrolysis and condensation of the titanium alkoxide, an inorganic TiO2 gel was moulded within the nanopore cavities of the alumina template. The nanocomposite object underwent two thermal treatments to stabilize and crystallize the TiO2. The morphology of the nanocomposite object was characterized by Field Emission Scanning Electron Microscopy (FESEM. The TiO2 nanotanks obtained have cylindrical shapes and are approximately 69 nm in diameter with a tank-to-tank distance of 26 nm. X-ray diffraction analyses performed by Transmission Electron Microscopy (TEM with selected area electron diffraction (SAED were used to investigate the TiO2 structure. The optical properties were studied using UV-Vis spectroscopy.

  10. Mechanistic characterization of aerobic alcohol oxidation catalyzed by Pd(OAc)(2)/pyridine including identification of the catalyst resting state and the origin of nonlinear [catalyst] dependence.

    Science.gov (United States)

    Steinhoff, Bradley A; Guzei, Ilia A; Stahl, Shannon S

    2004-09-15

    The Pd(OAc)(2)/pyridine catalyst system is one of the most convenient and versatile catalyst systems for selective aerobic oxidation of organic substrates. This report describes the catalytic mechanism of Pd(OAc)(2)/pyridine-mediated oxidation of benzyl alcohol, which has been studied by gas-uptake kinetic methods and (1)H NMR spectroscopy. The data reveal that turnover-limiting substrate oxidation by palladium(II) proceeds by a four-step pathway involving (1) formation of an adduct between the alcohol substrate and the square-planar palladium(II) complex, (2) proton-coupled ligand substitution to generate a palladium-alkoxide species, (3) reversible dissociation of pyridine from palladium(II) to create a three-coordinate intermediate, and (4) irreversible beta-hydride elimination to produce benzaldehyde. The catalyst resting state, characterized by (1)H NMR spectroscopy, consists of an equilibrium mixture of (py)(2)Pd(OAc)(2), 1, and the alcohol adduct of this complex, 1xRCH(2)OH. These in situ spectroscopic data provide direct support for the mechanism proposed from kinetic studies. The catalyst displays higher turnover frequency at lower catalyst loading, as revealed by a nonlinear dependence of the rate on [catalyst]. This phenomenon arises from a competition between forward and reverse reaction steps that exhibit unimolecular and bimolecular dependences on [catalyst]. Finally, overoxidation of benzyl alcohol to benzoic acid, even at low levels, contributes to catalyst deactivation by formation of a less active palladium benzoate complex.

  11. Splitting a C-O bond in dialkylethers with bis(1,2,4-tri-t-butylcyclopentadienyl) cerium-hydride does not occur by a sigma-bond metathesis pathway: a combined experimental and DFT computational study

    Energy Technology Data Exchange (ETDEWEB)

    Werkema, Evan; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Andersen, Richard

    2010-04-06

    Addition of diethylether to [1,2,4(Me3C)3C5H2]2CeH, abbreviated Cp'2CeH, gives Cp'2CeOEt and ethane. Similarly, di-n-propyl- or di-n-butylether gives Cp'2Ce(O-n-Pr) and propane or Cp'2Ce(O-n-Bu) and butane, respectively. Using Cp'2CeD, the propane and butane contain deuterium predominantly in their methyl groups. Mechanisms, formulated on the basis of DFT computational studies, show that the reactions begin by an alpha or beta-CH activation with comparable activation barriers but only the beta-CH activation intermediate evolves into the alkoxide product and an olefin. The olefin then inserts into the Ce-H bond forming the alkyl derivative, Cp'2CeR, that eliminates alkane. The alpha-CH activation intermediate is in equilibrium with the starting reagents, Cp'2CeH and the ether, which accounts for the deuterium label in the methyl groups of the alkane. The one-step sigma-bond metathesis mechanism has a much higher activation barrier than either of the two-step mechanisms.

  12. SANS study to probe nanoparticle dispersion in nanocomposite membranes of aromatic polyamide and functionalized silica nanoparticles.

    Science.gov (United States)

    Jadav, Ghanshyam L; Aswal, Vinod K; Singh, Puyam S

    2010-11-01

    Silica nanoparticles produced from organically functionalized silicon alkoxide precursors were incorporated into polyamide film to produce a silica-polyamide nanocomposite membrane with enhanced properties. The dispersion of the silica nanoparticles in the nanocomposite membrane was characterized by performing small-angle neutron scattering (SANS) measurements on dilute reactant systems and dilute solution suspensions of the final product. Clear scattering of monodisperse spherical particles of 10-18 A R(g) were observed from dilute solutions of the initial reactant system. These silica nanoparticles initially reacted with diamine monomers of polyamide and subsequently were transformed into polyamide-coated silica nanoparticles; finally nanoparticle aggregates of 27-45 A R(g) were formed. The nanoparticle dispersion of the membrane as the nanosized aggregates is in corroboration with ring- or chain-like assemblies of the nanoparticles dispersed in the bulk polyamide phase as observed by transmission electron microscopy. It is demonstrated that dispersions of silica nanoparticles as the nanosized aggregates in the polyamide phase could be achieved in the nanocomposite membrane with a silica content up to about 2 wt.%. Nanocomposite membranes with higher silica loading approximately 10 wt.% lead to the formation of large aggregates of sizes over 100 A R(g) in addition to the nanosized aggregates. Copyright 2010 Elsevier Inc. All rights reserved.

  13. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: A mechanistic study

    KAUST Repository

    Ahmed, Syud M.

    2013-12-18

    The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. © 2013 American Chemical Society.

  14. Metal-Free Alternating Copolymerization of CO2with Epoxides: Fulfilling “Green” Synthesis and Activity

    KAUST Repository

    Zhang, Dongyue

    2016-08-16

    Polycarbonates were successfully synthesized for the first time through the anionic copolymerization of epoxides with CO2, under metal-free conditions. Using an approach based on the activation of epoxides by Lewis acids and of CO, by appropriate cations, well-defined alternating copolymers made of CO, and propylene oxide (PO) or cyclohexene oxide (CHO) were indeed obtained. Triethyl borane was the Lewis acid chosen to activate the epoxides, and onium halides or onium alkoxides involving either ammonium, phosphonium, or phosphazenium cations were selected to initiate the copolymerization. In the case of PO, the carbonate content of the poly(propylene carbonate) formed was in the range of 92-99% and turnover numbers (TON) were close to 500; in the case of CHO perfectly alternating poly(cyclohexene carbonate) were obtained and TON values were close to 4000. The advantages of such a copolymerization system are manifold: (i) no need for multistep catalyst/ligand synthesis as in previous works; (ii) no transition metal involved in the copolymer synthesis and therefore no coloration of the samples isolated; and (iii) no necessity for postsynthesis purification.

  15. Flower-Like Mn-Doped CeO2 Microstructures: Synthesis, Characterizations, and Catalytic Properties

    Directory of Open Access Journals (Sweden)

    Ling Liu

    2015-01-01

    Full Text Available Mn-doped CeO2 flower-like microstructures have been synthesized by a facile method, involving the precipitation of metallic alkoxide precursor in a polyol process from the reaction of CeCl3·7H2O with ethylene glycol in the presence of urea followed by calcination. By introducing manganese ions, the composition can be freely manipulated. To investigate whether there was a hybrid synergic effect in CH4 combustion reaction, further detailed characteristics of Mn-doped CeO2 with various manganese contents were revealed by XRD, Raman, FT-IR, SEM, EDS, XPS, OSC, H2-TPR, and N2 adsorption-desorption measurements. The doping manganese is demonstrated to increase the storage of oxygen vacancy for CH4 and enhance the redox capability, which can efficiently convert CH4 to CO2 and H2O under oxygen-rich condition. The excellent catalytic performance of MCO-3 sample, which was obtained with the starting Mn/Ce ratios of 0.2 in the initial reactant compositions, is associated with the larger surface area and richer surface active oxygen species.

  16. Chemical Processing for Sol-Gel Derived Metal Oxide Thin Films using Supercritical Carbon Dioxide Fluid

    Energy Technology Data Exchange (ETDEWEB)

    Asai, Y; Narishige, S; Fujioka, K; Uchida, H; Koda, S, E-mail: uchidah@sophia.ac.jp [Sophia University, Department of Materials and Life Sciences, Tokyo 102-8554 (Japan)

    2011-10-29

    Chemical processing using supercritical carbon dioxide fluid (scCO{sub 2}) was demonstrated for lowering processing temperature of sol-gel-derived metal oxide thin films. The film processing was performed in a hot-wall closed vessel filled with scCO{sub 2} fluid. Precursor films of titanium dioxide (TiO{sub 2}) on soda-glass substrates prepared by sol-gel coating using Ti-alkoxide solution were converted to crystalline TiO{sub 2} (anatase) films successfully by the scCO{sub 2} treatment at a fluid pressure of 15 MPa and a substrate temperature of 300deg. C whereas no crystallization was occurred by conventional heat treatment at 400 deg. C. XPS analysis indicated that the interface reaction related to Si element was suppressed successfully by scCO{sub 2} treatment at 300 deg. C. These results suggest that the sol-gel synthesis using scCO{sub 2} fluid would be a cadidate for low-temperature processing of crystalline oxide films, which is more preferable than conventional techniques based on the heat treatment.

  17. Dynamics of supercooled confined water measured by deep inelastic neutron scattering

    Science.gov (United States)

    De Michele, Vincenzo; Romanelli, Giovanni; Cupane, Antonio

    2018-02-01

    In this paper, we present the results of deep inelastic neutron scattering (DINS) measurements on supercooled water confined within the pores (average pore diameter 20 Å) of a disordered hydrophilic silica matrix obtained through hydrolysis and polycondensation of the alkoxide precursor Tetra-Methyl-Ortho-Silicate via the sol-gel method. Experiments were performed at two temperatures (250 K and 210 K, i.e., before and after the putative liquid-liquid transition of supercooled confined water) on a "wet" sample with hydration h 40% w/w, which is high enough to have water-filled pores but low enough to avoid water crystallization. A virtually "dry" sample at h 7% was also investigated to measure the contribution of the silica matrix to the neutron scattering signal. As is well known, DINS measurements allow the determination of the mean kinetic energy and the momentum distribution of the hydrogen atoms in the system and therefore, allow researchers to probe the local structure of supercooled confined water. The main result obtained is that at 210 K the hydrogen mean kinetic energy is equal or even slightly higher than at 250 K. This is at odds with the predictions of a semiempirical harmonic model recently proposed to describe the temperature dependence of the kinetic energy of hydrogen in water. This is a new and very interesting result, which suggests that at 210 K, the water hydrogens experience a stiffer intermolecular potential than at 250 K. This is in agreement with the liquid-liquid transition hypothesis.

  18. Effect of Diethanolamine on Property of Thin Film TiO2 in Treating Hexavalent Chromium from Aqueous Solution

    International Nuclear Information System (INIS)

    Kajitvichyanukul, Puangrat; Jirapattarasakul, Sudarat

    2006-01-01

    In this research titanium dioxide thin film was synthesized from hydrolysis and condensation process by sol-gel method. Titanium alkoxide was used as initial substrate. The solvent was ethanal and the additive substance was diethanolamine. All substances are mixed altogether in different ratios. To study the effect of diethanolamine on properties of titanium dioxide thin film, various film analysis were performed which included mass weighing, adhesive test, corrosion test using acid and alkali, surface morphology analysis with scanning electron microscope (SEM), thin film structure analysis using X-ray diffraction (XRD), and photo activity by chromium removal test. It was found that diethanolmine enhanced the film strength and improved the adhesive property. The smooth surface was obtained. This thin film showed the effectiveness in chromium removal with high photo activity. Even tough the developed thin film can remove chromium (VI) efficiently, the reaction rate constant (k) was slightly reduced from that using the normal thin film titanium dioxide (without adding diethanolamine). In addition, the reaction time is required little longer to accomplish the chromium (VI) removal with the same performance

  19. Long-term high-level waste technology. Composite quarterly technical report, January-March 1981

    International Nuclear Information System (INIS)

    Cornman, W.R.

    1981-08-01

    This composite quarterly technical report summarizes work performed at participating sites to immobilize high-level radioactive wastes. The report is structured along the lines of the Work Breakdown Structure adopted for use in the High-Level Waste Management Technology program. These are: (1) program management and support with subtasks of management and budget, environmental and safety assessments, and other support; (2) waste preparation with subtasks of in-situ storage or disposal, waste retrieval, and separation and concentration; (3) waste fixation with subtasks of waste form development and characterization, and process and equipment development; and (4) final handling with subtasks of canister development and characterization and onsite storage or disposal. Some of the highlights are: preliminary event trees defining possible accidents were completed in the safety assessment of continued in-tank storage of high-level waste at Hanford; two low-cost waste forms (tailored concrete and bitumen) were investigated as candidate immobilization forms at the Hanford in-situ disposal studies of high-level waste; in comparative impact tests at the same impact energy per specimen volume, the same mass of respirable sizes was observed at ANL for SRL Frit 131 glass, SYNROC B ceramic, and SYNROC D ceramic; leaching tests were conducted on alkoxide glasses; glass-ceramic, concrete, and SYNROC D; a process design description was written for the tailored ceramic process

  20. Minute-made and low carbon fingerprint microwave synthesis of high quality templated mesoporous silica

    KAUST Repository

    Chaignon, J.

    2015-01-01

    © The Royal Society of Chemistry 2015. Hexagonal mesostructured templated silicas were produced in less than 10 minutes using an ultra-fast microwave assisted hydrothermal synthesis. Typically, 10 g can be prepared at once in a commercial microwave device usually devoted to analytical digestion. Undesired alcohol side-products were avoided using inexpensive water colloidal silica instead of silicon alkoxides as the silicon source. In comparison with classical heating activation, the absence of pore expansion and pore wall thickening even for synthesis temperatures as high as 190 °C evidenced that heat transfer and diffusion of matter had no time to take place. Comparison between the chemically extracted and calcined samples shows that the structure was better stabilized for autoclaving above 150 °C. However, a fast temperature ramping and final temperatures above 180 °C were required to sear structures of the highest quality comparable to that of the best conventional methods. This is rationalized by assuming a sequential flake-by-flake assembly of the pore-wall at the micelle palisade. Notably, tosylate counterions yielded better structural characteristics than bromide counterions and allowed better opportunities for surfactant recycling.

  1. One-pot synthesis and characterization of novel sodium tris(glycozirconate) and cerium glycolate precursors and their pyrolysis

    International Nuclear Information System (INIS)

    Ksapabutr, Bussarin; Gulari, Erdogan; Wongkasemjit, Sujitra

    2004-01-01

    A low-cost and facile route to the synthesis of bimetallic glycolato zirconate (Na 2 Zr(C 2 H 4 O 2 ) 3 ) and homometallic glycolato cerate (Ce(C 2 H 4 O 2 )), which can be used as alkoxide precursors for sodium zirconium oxide (and/or zirconia by sol-gel process) and ceria materials, has been developed from the reaction of inexpensive starting materials via the oxide one-pot synthesis (OOPS) process. Both complexes were directly synthesized from zirconium hydroxide/cerium hydroxide and ethylene glycol using base as catalyst. Sodium hydroxide was used in the synthesis of sodium tris(glycozirconate) complex while both triethylenetetramine (TETA) as catalyst and trace amount of sodium hydroxide as co-catalyst were used in the case of cerium glycolate complex. The structures of obtained products were investigated using FTIR, TGA, DSC, 1 H and 13 C NMR, elemental analyses, EDS and mass spectroscopy. Pyrolysis studies delineate the effects of temperature on the decomposition processes whereby sodium tris(glycozirconate) and cerium glycolate precursors transform into Na 2 O·ZrO 2 and CeO 2 , respectively. The resulting sodium zirconium oxide and ceria, after pyrolysis at 600 deg. C for 3 h, had BET surface areas of about 62 and 70 m 2 g -1 , respectively, and show monomodal pore size distributions in the mesopore region

  2. Synthesis of amorphous zirconium oxide with luminescent characteristics

    International Nuclear Information System (INIS)

    Barrera S, M.; Chavez G, M.; Soto E, A.M.; Velasquez O, C.; Garcia S, M.A.; Olvera T, L.; Rivera M, T.

    2004-01-01

    It was prepared zirconium oxide, ZrO 2 , by means of hydrolysis-condensation reactions (sol-gel method), using zirconium propoxide, Zr(C 3 H 7 O) 4 , as precursor and nitric acid, HNO 3 , as catalyst of the hydrolysis reaction. In this synthesis it was used a molar ratio water-alkoxide, r=n H2O /n Zr (C 3 H 7 0) 4 , high, similar to 200, so that the hydrolysis happens quickly and the nucleation and growth are completed in very little time. The solid was characterized with Ftir spectrophotometry, Differential thermal analysis (Dta), Thermal gravimetric analysis (T G), X-ray diffraction of powders, Scanning electron microscopy (Sem) and X-ray Dispersion energy (EDX). The ZrO 2 obtained by this way is amorphous even to 300 C and it consists of big aggregates. The amorphous ZrO 2 , presents thermoluminescent behavior, after it was irradiated with UV radiation and beta particles of 90 Sr/ 90 Y and it was thermally stimulated. (Author)

  3. Manufacturing and properties of inorganic porous materials. Mukishitsu tako zairyo no seizo to seishitsu

    Energy Technology Data Exchange (ETDEWEB)

    Daimon, M.; Okada, K. (Tokyo Inst. of Technology, Tokyo (Japan). Faculty of Engineering)

    1992-09-01

    As for the manufacturing of the inorganic porous materials, synthesis of the materials like zeolyte which have pores with crystal structure, gel formation that have included the formation of gel by neutralizing inorganic aqueous solution and the hydrolysis of metallic alkoxide, formation of gel in cement concrete, porous glass from phase decomposition, sintered porous material, and the formation methods of honeycom and fibers, are described. In general their properties are divided into four types such as solid property, surface property, solid-gas composite property and the property of pore. Inorganic porous materials are used as filter material or composite materials having single component gas phase which have properties like thermal insulation, soundproof and control of electric resistance. They are also used in all important chemical processes like separation, purification and concentration. Chemical activity in the surface has been important, and the function of the catalyst is decided by the surface properties. The change in the properties of the material by increasing and fixing effective surface area of the supportive materials is explained. 27 refs., 11 figs.,1 tab.

  4. Quantum dot based on tin/titanium mixed oxide doped with europium synthesized by protein sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Paganini, Paula P.; Felinto, Maria Claudia F.C., E-mail: paulapaganini@usp.b, E-mail: mfelinto@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Brito, Hermi F., E-mail: hefbrito@iq.usp.b [Universidade de Sao Paulo (IQ/USP), Sao Paulo, SP (Brazil). Inst. de Quimica. Lab. de Elementos do Bloco f

    2011-07-01

    Special luminescence biomarkers have been developed to find more sensitive fluoroimmunoassay methods. A new generation of these biomarkers is the semiconductors nanocrystals, known as quantum dots, doped with lanthanides. The use of lanthanides ions as luminescent markers has many advantages, for example a security method, low cost, high specificity and also the luminescence can be promptly measured with high sensibility and accuracy. The protein sol-gel is a modification of conventional method, in which the coconut water replacing the alkoxides normally used. The advantage is that, the proteins present in coconut water bind chemically with metal salts forming a polymer chain. This work presents nanoparticles based on tin/titanium mixed oxide doped with 3% of europium synthesized by protein sol-gel method. The nanoparticles were burned at 300 deg C, 500 deg C, 800 deg C and 1100 deg C. The samples were analyzed and characterized by thermal analysis, X-ray powder diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The synthesis was effective and the nanoparticles showed nanometric size and structural differences with the annealing. To be used in the fluoroimmunoassays tests, these particles need to be functionalized before be connect with biological molecules and after this process, these nanoparticles going to be submitted at gamma radiation for sterilization. (author)

  5. Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

    Science.gov (United States)

    Wang, Guangwei; Mohan, Swathi; Negishi, Ei-ichi

    2011-01-01

    All four stereoisomers (7–10) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (E)- and (Z)-β-bromoacrylates. Although the stereoisomeric purity of the 2Z,4E-isomer (8) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤ 95%, as reported earlier, the use of CsF or nBu4NF as a promoter base has now been found to give all of 7–10 in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2E,4E and 2E,4Z isomers of ≥98% purity, but the purity of the 2Z,4E isomer was ≤ 95%. Mutually complementary Horner–Wadsworth–Emmons and Still–Gennari (SG) olefinations are also of considerably limited scopes. Neither 2E,4Z nor 2Z,4Z isomer is readily prepared in ≥90% selectivity. In addition to (2Z,4E)-dienoic esters, some (2Z,4E,6E)- and (2Z,4E,6Z)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation–SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (23–30) have been prepared in ≥98% overall selectivity. PMID:21709262

  6. Encapsulation of titanium dioxide nanoparticles in PLA microspheres using supercritical emulsion extraction to produce bactericidal nanocomposites

    Science.gov (United States)

    Campardelli, R.; Della Porta, G.; Gomez, V.; Irusta, S.; Reverchon, E.; Santamaria, J.

    2013-10-01

    In this work, PLA microparticles containing TiO2 (anatase) nanoparticles have been produced using the Continuous Supercritical Emulsion Extraction technique (SEE-C). A stabilized anatase colloidal suspension (15 ± 5 nm) in ethanol aqueous solution was obtained by precipitation from solutions of titanium alkoxides and directly used as the water internal phase of a water-in-oil in water double emulsion or suspended as a powder in the organic phase of a solid-in-oil in water emulsion. Micro- (0.9 ± 0.5 μm) and submicro-particles (203 ± 40 nm) have been produced, with TiO2 nominal loadings of 1.2, 2.4, and 3.6 wt%. High TiO2 encapsulation efficiencies up to about 90 % have been obtained. PLA/TiO2 particles have been characterized by TEM and XPS to investigate the dispersion of the metal oxide in the polymeric matrix. The photo-assisted bactericidal activity of TiO2-containing microparticles against a biofilm-forming strain of Staphylococcus aureus was investigated in specific assays under UV light. Pure TiO2 nanoparticles and PLA/TiO2 particles showed the same bactericidal activity.

  7. Effective surface passivation of multi-shelled InP quantum dots through a simple complexing with titanium species

    Science.gov (United States)

    Jo, Jung-Ho; Kim, Min-Seok; Han, Chang-Yeol; Jang, Eun-Pyo; Do, Young Rag; Yang, Heesun

    2018-01-01

    Fluorescent efficiency of various visible quantum dots (QDs) has been incessantly improved to meet industrially high standard mainly through the advance in core/shell heterostructural design, however, their stability against degradable environments appears still lacking. The most viable strategy to cope with this issue was to exploit chemically inert oxide phases to passivate QD surface in the form of either individual overcoating or matrix embedding. Herein, we report a simple but effective means to passivate QD surface by complexing its organic ligands with a metal alkoxide of titanium isopropoxide (Ti(i-PrO)4). For this, highly efficient red-emitting InP QDs with a multi-shell structure of ZnSeS intermediate plus ZnS outer shell are first synthesized and then the surface of resulting InP/ZnSeS/ZnS QDs is in-situ decorated with Ti(i-PrO)4. The presence of Tisbnd O species from Ti(i-PrO)4 on QD surface is verified by x-ray photoelectron and Fourier transform infrared spectroscopic analyses. Two comparative dispersions of pristine versus Ti(i-PrO)4-complexed QDs are exposed for certain periods of time to UV photon and heat and their temporal changes in photoluminescence are monitored, resulting in a huge improvement in QD stability from the latter ones through Ti(i-PrO)4-mediated better surface passivation.

  8. MODIFICAÇÃO DE MEMBRANA DE POLIAMIDA VIA SOL-GEL E INCORPORAÇÃO DE COMPOSTO DE EURÓPIO (III LUMINESCENTE

    Directory of Open Access Journals (Sweden)

    Érica A. de Souza

    Full Text Available Over the last decades, the combination of different technologies to search for systems with new properties and features has brought various segments of biological and earth sciences together. Additive manufacturing, known as rapid prototyping, combined with the sol-gel methodology enables the production of novel systems with applications in many scientific fields. In this work, flexible polyamide membranes were obtained by additive manufacturing, functionalized by the sol-gel methodology, and incorporated with the coordination compound between Eu(III and 1,10-phenanthroline. The presence of vibrations at 1100 cm-1 in the FTIR spectrum of the material, which is a band typical of the Si-O-Si group in the alkoxide employed during the process, confirmed the polyamide membrane functionalization. The thermogravimetric curve showed that a residue remained after heating at 700 ºC, which was attributed to SiO2. The membrane was highly luminescent, which confirmed incorporation of the Eu3+ compound into the material and pointed to the possible application of this system as a topical medication for the treatment of skin diseases.

  9. Catalytic asymmetric aza-Morita-Baylis-Hillman reaction of methyl acrylate: role of a bifunctional La(O-iPr)3/linked-BINOL complex.

    Science.gov (United States)

    Yukawa, Takafumi; Seelig, Bianca; Xu, Yingjie; Morimoto, Hiroyuki; Matsunaga, Shigeki; Berkessel, Albrecht; Shibasaki, Masakatsu

    2010-09-01

    The catalytic asymmetric aza-Morita-Baylis-Hillman reaction using unactivated methyl acrylate is described. A simple Lewis acidic metal catalyst, such as La(OTf)(3), was not suitable for the reaction, but rare earth metal alkoxide/linked-BINOL complexes possessing bifunctional Lewis acid and Brønsted base properties efficiently promoted the reaction in combination with an achiral nucleophilic organocatalyst. The combined use of a La(O-iPr)(3)/(S,S)-TMS-linked-BINOL complex with a catalytic amount of DABCO promoted the aza-Morita-Baylis-Hillman reaction of a broad range of N-diphenylphosphinoyl imines. Products from aryl, heteroaryl, and alkenyl imines were obtained in 67-99% yield and 81-95% ee. It is noteworthy that isomerizable alkyl imines could be employed as well, giving products in 78-89% yield and 94-98% ee. Initial rate kinetic studies as well as kinetic isotope effect experiments using alpha-deuterio-methyl acrylate support the importance of both the nucleophilicity of La-enolate and the Brønsted basicity of a La-catalyst for promoting the reaction.

  10. Development of vapor deposited silica sol-gel particles for use as a bioactive materials system.

    Science.gov (United States)

    Snyder, Katherine L; Holmes, Hallie R; VanWagner, Michael J; Hartman, Natalie J; Rajachar, Rupak M

    2013-06-01

    Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15°) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis. Copyright © 2012 Wiley Periodicals, Inc.

  11. Partial Oxidation of n-Butane over a Sol-Gel Prepared Vanadium Phosphorous Oxide

    Directory of Open Access Journals (Sweden)

    Juan M. Salazar

    2013-01-01

    Full Text Available Vanadium phosphorous oxide (VPO is traditionally manufactured from solid vanadium oxides by synthesizing VOHPO4∙0.5H2O (the precursor followed by in situ activation to produce (VO2P2O7 (the active phase. This paper discusses an alternative synthesis method based on sol-gel techniques. Vanadium (V triisopropoxide oxide was reacted with ortho-phosphoric acid in an aprotic solvent. The products were dried at high pressure in an autoclave with a controlled excess of solvent. This procedure produced a gel of VOPO4 with interlayer entrapped molecules. The surface area of the obtained materials was between 50 and 120 m2/g. Alcohol produced by the alkoxide hydrolysis reduced the vanadium during the drying step, thus VOPO4 was converted to the precursor. This procedure yielded non-agglomerated platelets, which were dehydrated and evaluated in a butane-air mixture. Catalysts were significantly more selective than the traditionally prepared materials with similar intrinsic activity. It is suggested that the small crystallite size obtained increased their selectivity towards maleic anhydride.

  12. RBS analysis of electrochromic layers

    Energy Technology Data Exchange (ETDEWEB)

    Green, D.C.; Bell, J.M. [University of Technology, Sydney, NSW (Australia); Kenny, M.J.; Wielunski, L.S. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Lindfield, NSW (Australia). Div. of Applied Physics

    1993-12-31

    Tungsten oxide thin films produced by dip-coating from tungsten alkoxide solutions are of interest for their application in large area switchable windows. The application consists of a layer of electrochromic tungsten oxide (W0{sub 3}) on indium tin oxide (ITO) coated glass in contact with a complementary structure. Electrochromic devices are switchable between states of high and low transparency by the application of a small voltage. The mechanism relies on the dual injection of ions and electrons into the W0{sub 3} layer from adjacent layers in the device. Electrochromic tungsten oxide can be deposited using standard techniques (eg. sputtering and evaporation) but also using sol-gel deposition. Sol-gel processing has an advantage over conventional preparation techniques because of the simplicity of the equipment. The scaling up to large area coatings is also feasible. RBS and forward recoil has been used to obtain profiles for individual elements in the structure of electrochromic films. 3 refs., 3 figs.

  13. Coprecipitation synthesis and negative thermal expansion of NbVO5.

    Science.gov (United States)

    Wang, Jinrui; Deng, Jinxia; Yu, Ranbo; Chen, Jun; Xing, Xianran

    2011-04-07

    We develop a coprecipitation synthesis route to prepare NbVO(5) with simple oxide Nb(2)O(5) and NH(4)VO(3) as starting materials. No metal alkoxide or organometallic substance was used in the process. Nano-crystal NbVO(5) was obtained by calcination of the coprecipitates at 550 °C for 2 h. DSC/TG and XRD investigations indicate that the target compound NbVO(5) is completely formed up to 504.5 °C and is thermally stable below 658 °C. Rietveld XRD refinements give an orthorhombic structure with space group Pnma and lattice parameters, a=11.8453(2), b=5.5126(3) and c=6.9212(2) Å, respectively. In particular, HTXRD determinations show a negative thermal expansion in NbVO(5) with a TEC of -6.63 × 10(-6) °C(-1) in the temperature range of RT-600 °C. This fact is ascribed to the tilting of NbO(6) octahedra and VO(4) tetrahedra in the flexible framework structure. The present synthesis route is facile and easy to be extended to prepare analogues such as TaVO(5), etc. © The Royal Society of Chemistry 2011

  14. Vanadium oxide/polypyrrole aerogel nanocomposites. Technical report, 1 June 1995-31 May 1996

    Energy Technology Data Exchange (ETDEWEB)

    Dave, B.C.; Bunn, B.; Leroux, F.; Nazar, L.F.; Wong, H.P.

    1996-06-18

    Vanadium pentoxide/polypyrrole aerogel (ARG) nanocomposites were prepared by hydrolysis of VO(OC3H7)3 using pyrrole/water/acetone mixtures. Monolithic green-black gels with polypyrrole/V ratios ranging from 0.15 to 1.0 resulted from simultaneous polymerization of the pyrrole and vanadium alkoxide precursors. Supercritical drying yielded high surface (150-200 sq meters/g) aerogels, of sufficient mechanical integrity to allow them to be cut without fracturing. TEM studies of the aerogels show that they are comprised of fibers similar to that of V2O5 ARG`s, but with a much shorter chain length. Evidence from IR that the inorganic and organic components strongly interact leads us to propose that this impedes the vanadium condensation process. The result is ARG`s that exhibit decreased electronic conductivity with increasing polymer content. Despite the unexpected deleterious effect of the conductive polymer on the bulk conductivity, at low polymer content, the nanocomposite materials show enhanced electrochemical properties for Li insertion compared to the pristine aerogel.

  15. Vanadium oxide/polypyrrole aerogel nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Dave, B.C.; Dunn, B.S.; Wong, H.P. [Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering; Leroux, F.; Nazar, L.F. [Univ. of Waterloo, Ontario (Canada). Dept. of Chemistry

    1996-12-31

    Vanadium pentoxide/polypyrrole aerogel (ARG) nanocomposites were prepared by hydrolysis of VO(OC{sub 3}H{sub 7}){sub 3} using pyrrole/water/acetone mixtures. Monolithic green-black gels with polypyrrole/V ratios ranging from 0.15 to 1.0 resulted from simultaneously polymerization of the pyrrole and vanadium alkoxide precursors. Supercritical drying yielded high surface (150--200 m{sup 2}/g) aerogels, of sufficient mechanical integrity to allow them to be cut without fracturing. TEM studies of the aerogels show that they are comprised of fibers similar to that of V{sub 2}O{sub 5} ARG`s, but with a much shorter chain length. Evidence from IR that the inorganic and organic components strongly interact leads them to propose that this impedes the vanadium condensation process. The result is ARG`s that exhibit decreased electronic conductivity with increasing polymer content. Despite the unexpected deleterious effect of the conductive polymer on the bulk conductivity, at low polymer content, the nanocomposite materials show enhanced electrochemical properties for Li insertion compared to the pristine aerogel.

  16. Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification.

    Science.gov (United States)

    Nakatani, Kazuhiro; Ogura, Yusuke; Koda, Yuta; Terashima, Takaya; Sawamoto, Mitsuo

    2012-03-07

    Sequence regulation of monomers is undoubtedly a challenging issue as an ultimate goal in polymer science. To efficiently produce sequence-controlled copolymers, we herein developed the versatile tandem catalysis, which concurrently and/or sequentially involved ruthenium-catalyzed living radical polymerization and in situ transesterification of methacrylates (monomers: RMA) with metal alkoxides (catalysts) and alcohols (ROH). Typically, gradient copolymers were directly obtained from the synchronization of the two reactions: the instantaneous monomer composition in feed gradually changed via the transesterification of R(1)MA into R(2)MA in the presence of R(2)OH during living polymerization to give R(1)MA/R(2)MA gradient copolymers. The gradient sequence of monomers along a chain was catalytically controlled by the reaction conditions such as temperature, concentration and/or species of catalysts, alcohols, and monomers. The sequence regulation of multimonomer units was also successfully achieved in one-pot by monomer-selective transesterification in concurrent tandem catalysis and iterative tandem catalysis, providing random-gradient copolymers and gradient-block counterparts, respectively. In contrast, sequential tandem catalysis via the variable initiation of either polymerization or in situ transesterification led to random or block copolymers. Due to the versatile adaptability of common and commercially available reagents (monomers, alcohols, catalysts), this tandem catalysis is one of the most efficient, convenient, and powerful tools to design tailor-made sequence-regulated copolymers. © 2012 American Chemical Society

  17. Ferroelectric Polymer Composite with Enhanced Breakdown Strength

    Science.gov (United States)

    Han, Kuo; Gadinski, Matthew; Wang, Qing

    2013-03-01

    Numerous efforts have been made in the past decades to improve the energy storage capability of dielectric capacitors by incorporating ceramic addictives into polymers. Ferroelectric polymers have been particularly interesting as matrix for dielectric composites because of their highest dielectric permittivity and energy density. However, most polymer composites suffer from significantly reduced breakdown strength, which compromises the potential gain in energy density. In this work, various metallic alkoxide were introduced into the functionalized ferroelectric poly(vinylidene fluoride-co- chlorotrifluoroethylene), P(VDF-CTFE), via covalent bonding. The composite with the optimized composition exhibited the Weibull statistical breakdown strength of 504.8 MV/m, 67.6 % higher than the pristine polymer. The enhanced breakdown strength was mainly ascribed to the cross-linking and the formation of deep traps, which effectively reduced the conduction and further lowered the energy loss. Additionally, the homogeneous dispersion of the inorganic phase and the small contrast in permittivity between the polymer and amorphous oxides also contribute to the improved dielectric strength. The dielectric spectra of the composites have been recorded at varied temperatures and frequencies, which revealed the presence of the interfacial polarization layer in the composites.

  18. A practical technique for the fabrication of highly ordered macroporous structures of inorganic oxides

    International Nuclear Information System (INIS)

    Tang Fengqiu; Uchikoshi, Tetsuo; Sakka, Yoshio

    2006-01-01

    Well-defined macroporous ceramics consisting of SiO 2 , TiO 2 and ZrO 2 have been fabricated via a template-assisted colloidal processing technique. Close-packed polymer spheres were first prepared as a template using centrifugation or gravitational sedimentation, followed by infiltration with alkoxide precursors. The centrifugation should be preferred because it is a less time-consuming process and the materials are better ordered. The removal of the template beads was achieved by calcination of the organic-inorganic hybrids at appropriate temperatures, yielding well-ordered macroporous ceramics. The arrangement of the porous structures could be changing the preparation of the packed polymer templates. Some novel arrangements of macropores were obtained in these macroporous ceramics: a simple square-packed arrangement for SiO 2 , the coexistence of hexagonal close-packed and simple close-packed arrangements for TiO 2 , and face-centered cubic packed arrangement for ZrO 2 . The resulting highly structured ceramics could have applications in areas ranging from quantum electronics to photocatalysis and battery materials

  19. Encapsulation of biomaterials in porous glass-like matrices prepared via an aqueous colloidal sol-gel process

    Science.gov (United States)

    Liu, Dean-Mo; Chen, I-Wei

    2001-01-01

    The present invention provides a process for the encapsulation of biologically important proteins into transparent, porous silica matrices by an alcohol-free, aqueous, colloidal sol-gel process, and to the biological materials encapsulated thereby. The process is exemplified by studies involving encapsulated cytochrome c, catalase, myoglobin, and hemoglobin, although non-proteinaceous biomaterials, such as active DNA or RNA fragments, cells or even tissues, may also be encapsulated in accordance with the present methods. Conformation, and hence activity of the biomaterial, is successfully retained after encapsulation as demonstrated by optical characterization of the molecules, even after long-term storage. The retained conformation of the biomaterial is strongly correlated to both the rate of gelation and the subsequent drying speed of the encapsulatng matrix. Moreover, in accordance with this process, gelation is accelerated by the use of a higher colloidal solid concentration and a lower synthesis pH than conventional methods, thereby enhancing structural stability and retained conformation of the biomaterials. Thus, the invention also provides a remarkable improvement in retaining the biological activity of the encapsulated biomaterial, as compared with those involved in conventional alkoxide-based processes. It further provides new methods for the quantitative and qualitative detection of test substances that are reactive to, or catalyzed by, the active, encapsulated biological materials.

  20. Study of an industrial process for the synthesis of high molar mass ethylene oxide-propylene oxide copolymers usable as extrusible electrolyte; Etude d`un procede industriel de synthese de copolymeres oxyde d`ethylene-oxyde de propylene de hautes masses molaires utilisables comme electrolyte extrudable

    Energy Technology Data Exchange (ETDEWEB)

    Gramain, Ph. [Ecole Nationale Superieure de Chimie de Montpellier, 34 (France); Caselles, E. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France)

    1996-12-31

    The aim of this work is to develop an industrial process for the synthesis of an extrusible electrolyte polymer for lithium batteries. From literature data and precise specifications the high molar mass EO/OP copolymers synthesis by coordinative catalysis has been studied in order to reach a high productivity and to minimize the treatment steps. Two catalytic systems have been studied: the aluminium alkoxide-based Vandenberg-type catalysis and the calcium alcoholate amides catalysis. The first catalysis performed in solution gives excellent results. Its adaptation to silicon supported catalysis leads to a directly usable polymer in suspension but the productivity falls down and remains to be optimized. The calcium amide catalysis in heptane suspension generates acceptable productivities but also a too high proportion of low molar masses. Various approaches have been studied to minimize this proportion due to the presence of secondary sites that generate a cationic mechanism. The two synthesis ways explored are promising but remain to be optimized in order to increase the productivity of the efficient catalytic site and to reduce the formation of low molar masses generated by parasite catalytic sites. (J.S.) 9 refs.

  1. Cellular Silica Encapsulation for Development of Robust Cell Based Biosensors

    Science.gov (United States)

    Johnston, Robert; Rogelj, Snezna; Harper, Jason; Tartis, Michaelann

    2014-03-01

    In order to detect chemical and biological threats both on the battlefield and in civilian life, development of portable, robust detection systems capable of real-time identification of the chemical and biological agents are needed. Living cell-based sensors have proven effective as sensitive, specific, near real-time detectors; however, living cell-based sensors require frequent cell replenishment due to cell sensitivity to the ex-vivo environment, which limits sensor stability. Incorporation of living cells within a biocompatible matrix that provides mechanical protection and maintains access to the external environment may facilitate the development of long-term stable cell-based biosensors. We are exploring the use of a novel Chemical Vapor into Liquid (CViL) deposition process for whole cell encapsulation in silica. In CViL, the high vapor pressure of common silica alkoxides is utilized to deliver silica into an aqueous medium, creating a silica sol. Mixing of cells with the resulting silica sol facilitates encapsulation of cells in silica while minimizing cell contact with the cytotoxic products of silica generating reactions. Using fluorescence microscopy analysis with multiple silica specific markers, encapsulation of multiple eukaryotic cell types (Saccharomyces cerevisiae, Jurkat, HeLa, and U87 cells) with CViL generated silica is shown, providing a foundation for development of long -term stable cell-based biosensors with diverse sensing capabilities.

  2. Effect of chelating agent acetylacetone on corrosion protection properties of silane-zirconium sol–gel coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Mei, E-mail: yumei@buaa.edu.cn; Liang, Min; Liu, Jianhua; Li, Songmei; Xue, Bing; Zhao, Hao

    2016-02-15

    Graphical abstract: - Highlights: • AcAc was employed as a chelating agent in order to form stable sols. • The sol particle size depends on the concentration of AcAc. • AFM results indicate that AcAc content affects the morphology of the coatings. • Coating AcAc3 shows the optimal corrosion protection. - Abstract: The hybrid sol–gel coatings on AA2024-T3 were prepared with a silane coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) and a metal alkoxide tetra-n-propoxyzirconium (TPOZ) as precursors. The effect of acetylacetone (AcAc) as a chelating agent on the corrosion protection properties of sol–gel coatings were evaluated and the optimal AcAc/TPOZ molar ratio was obtained. The sol–gel coatings were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The corrosion protection properties of the coatings were evaluated by means of potentiodynamic polarization study (PDS) and electrochemical impedance spectroscopy (EIS). It is demonstrated that AcAc avoids fast hydrolysis of TPOZ and benefits to form stable sols. The coating with AcAc/TPOZ molar ratio of 3 shows the best corrosion protection performance in 0.05 M NaCl solution.

  3. Synthesis and characterization of alkoxy derivatives with double-headed initiators for the preparation of poly(ε-caprolactone-β-polyacrylonitrile (PCL-β-PAN and poly(l-lactide-β-polyacrylonitrile (PLLA-β-PAN copolymers

    Directory of Open Access Journals (Sweden)

    Taimur Athar

    2014-04-01

    Full Text Available The synthesis of simple single source molecular precursor based on metal alkoxides of the type,[(MMPEPAl(μ-OBnCH2Cl]2 (1,[(MMPEP-HLi·(BnOH]2 (2 and[(MMPEP-HLi·(HOB-nCH2Cl]2 (3 has been reported herein. Complex 1 was prepared by the reaction of[(MMPEPAl(CH3(Et2O] with p-(chloromethylbenzyl alcohol. The reaction of 2,2′-methylene-bis(4,6-di(1-methyl-1-phenylethylphenol (MMPEP-H2 with nBuLi, BnOH or p-(chloromethylbenzyl alcohol was added to give complexes 2 and 3, respectively. Among them, only complex 1 shows excellent catalytic properties towards ring-opening polymerization (ROP of ε-caprolactone. However, complexes 2 and 3 are active for ROP of l-lactide only. Block copolymers of poly(ε-caprolactone-β-polyacrylonitrile and poly(l-lactide-β-polyacrylonitrile were synthesized by using a technique known as atom transfer radical polymerization (ATRP and the ring opening polymerization (ROP. TEM micrograph of PCL-β-PAN shows the microphase property with the help of self-assembly.

  4. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING

    Energy Technology Data Exchange (ETDEWEB)

    LICHTENBERGER, DENNIS L.

    2002-03-26

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems.

  5. Preparation of silica by sol-gel method using formamide

    Directory of Open Access Journals (Sweden)

    R.F.S. Lenza

    2001-07-01

    Full Text Available In this work we obtained microporous and mesoporous silica gels by sol-gel processing. Tetraethylortosilicate (TEOS was used as precursor. Nitric acid and hydrofluoric acid were used as catalysts. In order to study the affect of formamide as drying additive, we used a molar ratio alkoxide/formamide of 1/1. The performance of formamide in obtaining crack-free gels was evaluated through monolithicity measurements. The structural evolution occurring in the interconnected network of the gels during thermal treatment was monitored by Fourier transform infrared spectroscopy (FTIR, shrinkage and density measurements and nitrogen gas sorption. We noted that in the presence of formamide, the Si-O-Si bonds are stronger and belong to a more cross-linked structure. The samples obtained in the presence of formamide have larger pore volume and its pore structure is in the range of mesoporosity. The samples obtained without additive are microporous. Formamide allowed the preparation of crack-free silica gels stabilized at high temperatures.

  6. Temperature dependence of Young's modulus for Ca(1-x)SrxTiO3 Perovskite structures

    International Nuclear Information System (INIS)

    Daniels, J.; Finlayson, T.R.; Latella, B.A.; Liu, T.; Thomson, S.K.; Vance, E.R.

    2003-01-01

    Full text: The CaTiO 3 -SrTiO 3 series of perovskites exhibits a variety of structural transformations. The focus of the present work is to examine whether these mostly weak second-order transformations can be revealed by anomalies in the temperature dependence of the elastic modulus. Samples containing 50, 60 and 70 mole% Sr were studied for this purpose at temperatures between 77 and 800K. The samples were prepared by graphite die hot-pressing of powders prepared by the liquid alkoxide/nitrate method to achieve near-theoretical density. The Young's modulus measurements below room temperature were made by attaching a bar-shaped sample to a quartz crystal and measuring the resonant frequency, while those at elevated temperatures were carried out by an impulse exitation technique, again using a bar specimen. Data above room temperature for Sr 0.5 Ca 0.5 TiO 3 agreed well with previous data obtained by Redfern, and new data have been obtained below room temperature for each sample. The reducing conditions imposed by the use of graphite die hot-pressing have no observable effect on the data; Raman scattering data on hot-pressed Sr 0.7 Ca 0.3 TiO 3 showed the structural transformation at ∼230K as observed by others on material prepared by sintering in air

  7. Epoxy Sol-Gel Hybrid Thermosets

    Directory of Open Access Journals (Sweden)

    Angels Serra

    2016-02-01

    Full Text Available Sol-gel methodologies are advantageous in the preparation of hybrid materials in front of the conventional addition of nanoparticles, because of the fine dispersion of the inorganic phase that can be reached in epoxy matrices. In addition, the use of organoalkoxysilanes as coupling agents allows covalent linkage between organic and inorganic phases, which is the key point in the improvement of mechanical properties. The sol-gel process involves hydrolysis and condensation reactions under mild conditions, starting from hydrolysable metal alkoxides, generally alkoxy silanes. Using the sol-gel procedure, the viscosity of the formulation is maintained, which is an important issue in coating applications, whereas the transparency of the polymer matrix is also maintained. However, only the proper combination of the chemistries and functionalities of both organic and inorganic structures leads to thermosets with the desired characteristics. The adequate preparation of hybrid epoxy thermosets enables their improvement in characteristics such as mechanical properties (modulus, hardness, scratch resistance, thermal and flame resistance, corrosion and antimicrobial protection, and even optical performance among others.

  8. Sol-Gel Synthesis and Characterization of Cubic Bismuth Zinc Niobium Oxide Nanopowders

    Directory of Open Access Journals (Sweden)

    Ganchimeg Perenlei

    2014-01-01

    Full Text Available Bismuth zinc niobium oxide (BZN was successfully synthesized by a diol-based sol-gel reaction utilizing metal acetate and alkoxide precursors. Thermal analysis of a liquid suspension of precursors suggests that the majority of organic precursors decompose at temperatures up to 150°C, and organic free powders form above 350°C. The experimental results indicate that a homogeneous gel is obtained at about 200°C and then converts to a mixture of intermediate oxides at 350–400°C. Finally, single-phased BZN powders are obtained between 500 and 900°C. The degree of chemical homogeneity as determined by X-ray diffraction and EDS mapping is consistent throughout the samples. Elemental analysis indicates that the atomic ratio of metals closely matches a Bi1.5ZnNb1.5O7 composition. Crystallite sizes of the BZN powders calculated from the Scherrer equation are about 33–98 nm for the samples prepared at 500–700°C, respectively. The particle and crystallite sizes increase with increased sintering temperature. The estimated band gap of the BZN nanopowders from optical analysis is about 2.60–2.75 eV at 500-600°C. The observed phase formations and measured results in this study were compared with those of previous reports.

  9. Kinetics of adsorptive removal of DEClP and GB on impregnated Al2O3 nanoparticles.

    Science.gov (United States)

    Saxena, Amit; Srivastava, Avanish K; Singh, Beer; Gupta, Arvind K; Suryanarayana, Malladi V S; Pandey, Pratibha

    2010-03-15

    Nanoparticles of AP-Al(2)O(3) (aero-gel produced alumina) have been produced by an alkoxide based synthesis involving aluminum powder, methanol, toluene and water. Thus produced alumina nanoparticles were characterized and the data indicated the formation of nanoparticles of alumina in the size range of 2-30 nm with high surface area (375 m(2)/g). Thereafter, these nanoparticles were impregnated with reactive chemicals. Adsorptive removal kinetics for DEClP (diethylchlorophosphate) and GB (isopropylmethylphosphonofluoridate, sarin) was monitored by GC-FID (gas chromatograph coupled with flame ionization detector) technique and found to be following pseudo first order reaction kinetics. Among impregnated AP-Al(2)O(3) nanoparticles based sorbent systems AP-Al(2)O(3) impregnated with 9-molybdo-3-vanadophosphoric acid (10%, w/w) was found to be the most reactive with least half-life values of 7 and 30 min for the removal of DEClP and GB, respectively, whereas unimpregnated AP-Al(2)O(3) nanoparticles showed the best adsorption potential among all studied systems. In addition to this, hydrolysis reaction {identified using GC/MS (gas chromatograph coupled with mass spectrometer) technique} was found to be the route of degradation of DEClP and GB on impregnated alumina nanoparticles. (c) 2009 Elsevier B.V. All rights reserved.

  10. Estudio de la hidrólisis del trietilborato por espectroscopía infrarroja: evaluación de geles de borosilicato

    Directory of Open Access Journals (Sweden)

    Peña-Alonso, R.

    2007-10-01

    Full Text Available Triethylborate (TEB is a boron alkoxide largely used in the synthesis of sol-gel prepared materials. This method requires the hydrolysis and condensation of the synthesis reagents, usually alkoxides, for obtaining a gel which can be transformed into different materials, such as glasses or ceramics, as a function of the thermal treatment applied. Infrared spectroscopy is one of the routine techniques used in the study of the sol-gel reaction due to the easy handling of the sample and the fast speed of the analysis. In this work, the study of the hydrolysis and condensation reactions of TEB is carried out by studying their vibrational bands located at 893 cm-1, which shows a continuous decrease as the hydrolysis is performed, and 1194 cm-1, which increases with the proceed of the condensation. A proposed calibration line for the quantitative analysis of the hydrolysis extension of TEB in several TEOS-TEB gels evidence that between 20 and 33% of the TEB molecules have not been hydrolysed during the sol-gel reaction for forming such gels.

    El trietilborato (TEB es un alcóxido de boro muy usado en las síntesis de materiales preparados por el método sol-gel. Este método implica la hidrólisis y condensación de los reactivos de síntesis, generalmente alcóxidos, para obtener un gel que posteriormente puede dar lugar a diversos tipos de materiales, tanto cerámicos como vítreos, dependiendo del tratamiento térmico posterior. Una de las técnicas de rutina empleadas en el seguimiento de las reacciones sol-gel es la espectroscopía infrarroja por la facilidad de manipulación de la muestra y rapidez del análisis. En este trabajo se realiza un estudio de las reacciones de hidrólisis y condensación del alcóxido TEB a través del seguimiento de las bandas de absorción situadas a 893 cm-1, que muestra una disminución a medida que avanza la hidrólisis del alcóxido, y 1194 cm-1 que crece con el avance de la condensación. La recta de

  11. Synthesis and characterization of polyhedral oligomeric titanized silsesquioxane: A new biocompatible cage like molecule for biomedical application

    Energy Technology Data Exchange (ETDEWEB)

    Yahyaei, Hossein [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Mohseni, Mohsen, E-mail: mmohseni@aut.ac.ir [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Ghanbari, Hossein [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences (TUMS), Tehran (Iran, Islamic Republic of); Messori, Massimo [Dipartimento di Ingegneria ‘Enzo Ferrari’, Università di Modena e Reggio Emilia, Modena (Italy)

    2016-04-01

    Organic–inorganic hybrid materials have shown improved properties to be used as biocompatible coating in biomedical applications. Polyhedral oligomeric silsesquioxane (POSS) containing coatings are among hybrid materials showing promising properties for these applications. In this work an open cage POSS has been reacted with a titanium alkoxide to end cap the POSS molecule with titanium atom to obtain a so called polyhedral oligomeric metalized silsesquioxane (POMS). The synthesized POMS was characterized by FTIR, RAMAN and UV–visible spectroscopy as well as {sup 29}Si NMR and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) techniques. Appearance of peaks at 920 cm{sup −1} in FTIR and 491 cm{sup −1} and 1083 cm{sup −1} in Raman spectra confirmed Si–O–Ti linkage formation. It was also demonstrated that POMS was in a monomeric form. To evaluate the biocompatibility of hybrids films, pristine POSS and synthesized POMS were used in synthesis of a polycarbonate urethane polymer. Results revealed that POMS containing hybrid, not only had notable thermal and mechanical stability compared to POSS containing one, as demonstrated by DSC and DMTA analysis, they also showed controlled surface properties in such a manner that hydrophobicity and biocompatibility were both reachable to give rise to improved cell viability in presence of human umbilical vein endothelial cells (HUVEC) and MRC-5 cells. - Highlight: • Polyhedral Oligomeric Metalized Silsesquioxane (POMS) based on titanium was synthesized. • POMS can improve mechanical properties of polyurethane. • POMS increases hydrophobicity of polyurethane. • POMS is a unique nanocage to enhance biocompatibility of polyurethane.

  12. Probing the reaction mechanism of IspH protein by x-ray structure analysis

    KAUST Repository

    Gräwert, Tobias

    2009-12-28

    Isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) represent the two central intermediates in the biosynthesis of isoprenoids. The recently discovereddeoxyxylulose 5-phosphate pathway generates a mixture of IPP and DMAPP in its final step by reductive dehydroxylation of 1-hydroxy-2-methyl- 2-butenyl 4-diphosphate. This conversion is catalyzed by IspH protein comprising a central iron-sulfur cluster as electron transfer cofactor in the active site. The five crystal structures of IspH in complex with substrate, converted substrate, products and PPi reported in this article provide unique insights into the mechanism of this enzyme. While IspH protein crystallizes with substrate bound to a [4Fe-4S] cluster, crystals of IspH in complex with IPP, DMAPP or inorganic pyrophosphate feature [3Fe-4S] clusters. The IspH:substrate complex reveals a hairpin conformation of the ligand with the C(1) hydroxyl group coordinated to the unique site in a [4Fe-4S] cluster of aconitase type. The resulting alkoxide complex is coupled to a hydrogen-bonding network, which serves as proton reservoir via a Thr167 proton relay. Prolonged x-ray irradiation leads to cleavage of the C(1)-O bond (initiated by reducing photo electrons). The data suggest a reaction mechanism involving a combination of Lewis-acid activation and proton coupled electron transfer. The resulting allyl radical intermediate can acquire a second electron via the iron-sulfur cluster. The reaction may be terminated by the transfer of a proton from the β-phosphate of the substrate to C(1) (affording DMAPP) or C(3) (affording IPP).

  13. In situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion as potential electrode materials for energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Mombrú, Dominique [Centro NanoMat/CryssMat/Física – DETEMA – Facultad de Química – Universidad de la República, C.P. 11800 Montevideo (Uruguay); Romero, Mariano, E-mail: mromero@fq.edu.uy [Centro NanoMat/CryssMat/Física – DETEMA – Facultad de Química – Universidad de la República, C.P. 11800 Montevideo (Uruguay); Faccio, Ricardo, E-mail: rfaccio@fq.edu.uy [Centro NanoMat/CryssMat/Física – DETEMA – Facultad de Química – Universidad de la República, C.P. 11800 Montevideo (Uruguay); Castiglioni, Jorge [Laboratorio de Fisicoquímica de Superficies – DETEMA – Facultad de Química – Universidad de la República, C.P. 11800 Montevideo (Uruguay); Mombrú, Alvaro W., E-mail: amombru@fq.edu.uy [Centro NanoMat/CryssMat/Física – DETEMA – Facultad de Química – Universidad de la República, C.P. 11800 Montevideo (Uruguay)

    2017-06-15

    In situ preparation of polyaniline-ceramic nanocomposites has recently demonstrated that the electrical properties are highly improved with respect to the typical ex situ preparations. In this report, we present for the first time, to the best of our knowledge, the in situ growth of titanium oxide quantum dots in polyaniline host via water vapor flow diffusion as an easily adaptable route to prepare other ceramic-polymer nanocomposites. The main relevance of this method is the possibility to prepare ceramic quantum dots from alkoxide precursors using water vapor flow into any hydrophobic polymer host and to achieve good homogeneity and size-control. In addition, we perform full characterization by means of high-resolution transmission electron microscopy, X-ray powder diffraction, small angle X-ray scattering, thermogravimetric and calorimetric analyses, confocal Raman microscopy and impedance spectroscopy analyses. The presence of the polymer host and interparticle Coulomb repulsive interactions was evaluated as an influence for the formation of ~3–8 nm equally-sized quantum dots independently of the concentration. The polyaniline polaron population showed an increase for the quantum dots diluted regime and the suppression at the concentrated regime, ascribed to the formation of chemical bonds at the interface, which was confirmed by theoretical simulations. In agreement with the previous observation, the in situ growth of ceramic quantum dots in polyaniline host via water vapor flow diffusion could be very useful as a novel approach to prepare electrode materials for energy conversion and storage applications. - Highlights: • In situ growth of titanium oxide quantum dots in polyaniline host via water vapor flow diffusion. • Polyaniline charge carriers at the interface and charge interactions between quantum dots. • Easy extrapolation to sol-gel derived quantum dots into polymer host as potential electrode materials.

  14. Oxidative Dehydrogenation of Cyclohexane on Cobalt Oxide (Co3O4) Nanoparticles: The Effect of Particle Size on Activity and Selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Tyo, Eric C.; Yin, Chunrong; Di Vece, Marcel; Qian, Qiang; Kwon, Gihan; Lee, Sungsik; Lee, Byeongdu; DeBartolo, Janae E.; Seifert, Sönke; Winans, Randall E.; Si, Rui; Ricks, Brian; Goergen, Simone; Rutter, Matthew; Zugic, Branko; Flytzani-Stephanopoulos, Maria; Wang, Zhi Wei; Palmer, Richard E.; Neurock, Matthew; Vajda, Stefan

    2012-10-02

    The oxidative dehydrogenation of cyclohexane by cobalt oxide nanoparticles was studied via temperature programmed reaction combined with in situ grazing incidence X-ray absorption spectroscopy and grazing incidence small-angle X-ray scattering and theoretical calculations on model Co3O4 substrates. Both 6 and 12 nm Co3O4 nanoparticles were made through a surfactant-free preparation and dispersed on an Al2O3 surface formed by atomic layer deposition. Under reaction conditions the nanoparticles retained their oxidation state and did not sinter. They instead underwent an assembly/disassembly process and could reorganize within their assemblies. The selectivity of the catalyst was found to be size- and temperature-dependent, with larger particles preferentially producing cyclohexene at lower temperatures and smaller particles predominantly resulting in benzene at higher temperatures. The mechanistic features thought to control the oxidative dehydrogenation of cyclohexane and other light alkanes on cobalt oxide were established by carrying out density functional theory calculations on the activation of propane, a surrogate model alkane, over model Co3O4 surfaces. The initial activation of the alkane (propane) proceeds via hydrogen abstraction over surface oxygen sites. The subsequent activation of the resulting alkoxide intermediate occurs at a second surface oxygen site to form the alkene (propene) which then desorbs from the surface. Hydroxyl recombination results in the formation of water which desorbs from the surface. Finally, oxygen is necessary to regenerate the surface oxygen sites, catalyze C–H activation steps, and minimize catalyst degradation.

  15. Sol-gel preparation of silica and titania thin films

    Science.gov (United States)

    Thoř, Tomáš; Václavík, Jan

    2016-11-01

    Thin films of silicon dioxide (SiO2) and titanium dioxide (TiO2) for application in precision optics prepared via the solgel route are being investigated in this paper. The sol-gel process presents a low cost approach, which is capable of tailoring thin films of various materials in optical grade quality. Both SiO2 and TiO2 are materials well known for their application in the field of anti-reflective and also highly reflective optical coatings. For precision optics purposes, thickness control and high quality of such coatings are of utmost importance. In this work, thin films were deposited on microscope glass slides substrates using the dip-coating technique from a solution based on alkoxide precursors of tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TIP) for SiO2 and TiO2, respectively. As-deposited films were studied using spectroscopic ellipsometry to determine their thickness and refractive index. Using a semi-empirical equation, a relationship between the coating speed and the heat-treated film thickness was described for both SiO2 and TiO2 thin films. This allows us to control the final heat-treated thin film thickness by simply adjusting the coating speed. Furthermore, films' surface was studied using the white-light interferometry. As-prepared films exhibited low surface roughness with the area roughness parameter Sq being on average of 0.799 nm and 0.33 nm for SiO2 and TiO2, respectively.

  16. A new sol-gel synthesis of 45S5 bioactive glass using an organic acid as catalyst.

    Science.gov (United States)

    Faure, J; Drevet, R; Lemelle, A; Ben Jaber, N; Tara, A; El Btaouri, H; Benhayoune, H

    2015-02-01

    In this paper a new sol-gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol-gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol-gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2M nitric acid solution or either a 5mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer-Emmett-Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol-gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol-gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol-gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol-gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Atomic-resolution structures of horse liver alcohol dehydrogenase with NAD(+) and fluoroalcohols define strained Michaelis complexes.

    Science.gov (United States)

    Plapp, Bryce V; Ramaswamy, S

    2012-05-15

    Structures of horse liver alcohol dehydrogenase complexed with NAD(+) and unreactive substrate analogues, 2,2,2-trifluoroethanol or 2,3,4,5,6-pentafluorobenzyl alcohol, were determined at 100 K at 1.12 or 1.14 Å resolution, providing estimates of atomic positions with overall errors of ~0.02 Å, the geometry of ligand binding, descriptions of alternative conformations of amino acid residues and waters, and evidence of a strained nicotinamide ring. The four independent subunits from the two homodimeric structures differ only slightly in the peptide backbone conformation. Alternative conformations for amino acid side chains were identified for 50 of the 748 residues in each complex, and Leu-57 and Leu-116 adopt different conformations to accommodate the different alcohols at the active site. Each fluoroalcohol occupies one position, and the fluorines of the alcohols are well-resolved. These structures closely resemble the expected Michaelis complexes with the pro-R hydrogens of the methylene carbons of the alcohols directed toward the re face of C4N of the nicotinamide rings with a C-C distance of 3.40 Å. The oxygens of the alcohols are ligated to the catalytic zinc at a distance expected for a zinc alkoxide (1.96 Å) and participate in a low-barrier hydrogen bond (2.52 Å) with the hydroxyl group of Ser-48 in a proton relay system. As determined by X-ray refinement with no restraints on bond distances and planarity, the nicotinamide rings in the two complexes are slightly puckered (quasi-boat conformation, with torsion angles of 5.9° for C4N and 4.8° for N1N relative to the plane of the other atoms) and have bond distances that are somewhat different compared to those found for NAD(P)(+). It appears that the nicotinamide ring is strained toward the transition state on the path to alcohol oxidation.

  18. Facile sonochemical synthesis of amorphous NiFe-(oxy)hydroxide nanoparticles as superior electrocatalysts for oxygen evolution reaction.

    Science.gov (United States)

    Lee, Eunjik; Park, Ah-Hyeon; Park, Hyun-Uk; Kwon, Young-Uk

    2018-01-01

    In this work, we present facile synthesis of amorphous Ni/Fe mixed (oxy)hydroxide (NiFe(H)) nanoparticles (NPs) and their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media. a-NiFe(H) NPs have received lots of attention as OER electrocatalysts with many desirable properties. By using a simple sonochemical route, we prepared amorphous Ni and Fe-alkoxide (NiFe(A)) NPs whose composition can be controlled in the entire composition range (Ni 100-x Fe x , 0≤x≤1). These samples are composed of extremely small NiFe(A) NPs with Ni and Fe atoms homogeneously distributed. NiFe(A) NPs are readily converted into corresponding electrocatalytically active NiFe(H) NP by a simple electrochemical treatment. Electrochemical analysis data show that the OER activity of amorphous NiFe(H) samples follows the volcano-type trend when plotted against the Fe content. Ni 70 Fe 30 (H) sample showed the lowest overpotential of 292mV at 10mAcm -2 geo and the lowest Tafel slope of 30.4mVdec -1 , outperforming IrO x /C (326mV, 41.7mVdec -1 ). Our samples are highly durable based on the chronopotentiometry data at the current density of 10mAcm -2 geo for 2h which show that Ni 70 Fe 30 sample maintains the steady-state potential, contrary to the time-varying IrO x /C. Copyright © 2017 Elsevier B.V. All rights reserved.

  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. Hydroxyapatite-TiO(2)-based nanocomposites synthesized in supercritical CO(2) for bone tissue engineering: physical and mechanical properties.

    Science.gov (United States)

    Salarian, Mehrnaz; Xu, William Z; Wang, Zhiqiang; Sham, Tsun-Kong; Charpentier, Paul A

    2014-10-08

    Calcium phosphate-based nanocomposites offer a unique solution toward producing scaffolds for orthopedic and dental implants. However, despite attractive bioactivity and biocompatibility, hydroxyapatite (HAp) has been limited in heavy load-bearing applications due to its intrinsically low mechanical strength. In this work, to improve the mechanical properties of HAp, we grew HAp nanoplates from the surface of one-dimensional titania nanorod structures by combining a coprecipitation and sol-gel methodology using supercritical fluid processing with carbon dioxide (scCO2). The effects of metal alkoxide concentration (1.1-1.5 mol/L), reaction temperature (60-80 °C), and pressure (6000-8000 psi) on the morphology, crystallinity, and surface area of the resulting nanostructured composites were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET) method. Chemical composition of the products was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) analyses. HAp nanoplates and HAp-TiO2 nanocomposites were homogeneously mixed within poly(ε-caprolactone) (PCL) to develop scaffolds with enhanced physical and mechanical properties for bone regeneration. Mechanical behavior analysis demonstrated that the Young's and flexural moduli of the PCL/HAp-TiO2 composites were substantially higher than the PCL/HAp composites. Therefore, this new synthesis methodology in scCO2 holds promise for bone tissue engineering with improved mechanical properties.

  1. Screening Precursor-Solvent Combinations for Li4Ti5O12Energy Storage Material Using Flame Spray Pyrolysis.

    Science.gov (United States)

    Meierhofer, Florian; Li, Haipeng; Gockeln, Michael; Kun, Robert; Grieb, Tim; Rosenauer, Andreas; Fritsching, Udo; Kiefer, Johannes; Birkenstock, Johannes; Mädler, Lutz; Pokhrel, Suman

    2017-11-01

    The development and industrial application of advanced lithium based energy-storage materials are directly related to the innovative production techniques and the usage of inexpensive precursor materials. Flame spray pyrolysis (FSP) is a promising technique that overcomes the challenges in the production processes such as scalability, process control, material versatility, and cost. In the present study, phase pure anode material Li 4 Ti 5 O 12 (LTO) was designed using FSP via extensive systematic screening of lithium and titanium precursors dissolved in five different organic solvents. The effect of precursor and solvent parameters such as chemical reactivity, boiling point, and combustion enthalpy on the particle formation either via gas-to-particle (evaporation/nucleation/growth) or via droplet-to-particle (precipitation/incomplete evaporation) is discussed. The presence of carboxylic acid in the precursor solution resulted in pure (>95 mass %) and homogeneous LTO nanoparticles of size 4-9 nm, attributed to two reasons: (1) stabilization of water sensitive metal alkoxides precursor and (2) formation of volatile carboxylates from lithium nitrate evidenced by attenuated total reflection Fourier transform infrared spectroscopy and single droplet combustion experiments. In contrast, the absence of carboxylic acids resulted in larger inhomogeneous crystalline titanium dioxide (TiO 2 ) particles with significant reduction of LTO content as low as ∼34 mass %. In-depth particle characterization was performed using X-ray diffraction with Rietveld refinement, thermogravimetric analysis coupled with differential scanning calorimetry and mass spectrometry, gas adsorption, and vibrational spectroscopy. High-resolution transmission electron microscopy of the LTO product revealed excellent quality of the particles obtained at high temperature. In addition, high rate capability and efficient charge reversibility of LTO nanoparticles demonstrate the vast potential of

  2. Direct Partial Oxidations Using Molecular Oxygen - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Richard [Univ. of New Mexico, Albuquerque, NM (United States)

    2017-11-01

    In 2006, Richard A. Kemp (University of New Mexico) and Karen I. Goldberg (University of Washington) formed a team and began to investigate new strategies to accomplish direct selective aerobic oxidations, with a particular emphasis on the epoxidation of propylene and higher olefins. This DOE-BES funded project was renewed twice and concluded after a no-cost extension earlier this year. Multiple novel strategies involving homogeneous catalyst systems were initiated and investigated during the award. Important fundamental understanding and insight concerning requirements for promotion of aerobic olefin epoxidation was generated. During the tenure of this project, new knowledge was generated concerning the synthesis, characterization and aerobic reactivity of metal hydrides and hydroxides. Key results describing synthetic strategies and optimization of the preparation of mononuclear late metal hydrides were published. The team reported the first example of O2 insertion into a Pd-H bond, a reaction which had been proposed in the literature but never previously observed. Our experimental investigation of the mechanism was later followed by computational work, and a description of what is now referred to as the Hydrogen Atom Abstraction (HAA) pathway for this reaction has been widely accepted in the community. After investigation of many other late metal hydrides, both experimentally and computationally, the team put together a chapter that included a description of key contributing factors that allow reaction by the HAA mechanism. A brief sampling of other classic papers from our project include hydrogenolysis reactions of late metal hydroxide and alkoxide complexes, the synthesis of nickel-hydrides, and the involvement of hemilabile ligands in promoting new reaction pathways.

  3. Titania-coated manganite nanoparticles: Synthesis of the shell, characterization and MRI properties

    Energy Technology Data Exchange (ETDEWEB)

    Jirák, Zdeněk; Kuličková, Jarmila [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Herynek, Vít [Institute for Clinical and Experimental Medicine, Vídeňská 1958/9, 140 21 Praha 4 (Czech Republic); Maryško, Miroslav [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); Koktan, Jakub [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic); University of Chemistry and Technology, Prague, Technická 5, 166 28 Praha 6 (Czech Republic); Kaman, Ondřej, E-mail: kamano@seznam.cz [Institute of Physics, AS CR, Cukrovarnická 10, 162 00 Praha 6 (Czech Republic)

    2017-04-01

    Novel procedure for coating of oxide nanoparticles with titania, employing hydrolysis and polycondensation of titanium alkoxides under high-dilution conditions and cationic surfactants, is developed and applied to magnetic cores of perovskite manganite. Bare particles of the ferromagnetic La{sub 0.65}Sr{sub 0.35}MnO{sub 3} phase, possessing high magnetization, M{sub 10} {sub kOe}(4.5 K) = 63.5 emu g{sup −1}, and Curie temperature, T{sub C} = 355 K, are synthesized by sol-gel procedure and subsequently coated with titania. Further, a comparative silica-coated product is prepared. In order to analyse the morphology, colloidal stability, and surface properties of these two types of coated particles, a detailed study by means of transmission electron microscopy, dynamic light scattering, zeta-potential measurements, and IR spectroscopy is carried out. The experiments on the titania-coated sample reveal a continuous though porous character of the TiO{sub 2} shell, the nature of which is amorphous but can be transformed to anatase at higher temperatures. Finally, the relaxometric study at the magnetic field of 0.5 T, performed to quantity the transverse relaxivity and its temperature dependence, reveals important differences between the titania-coated and silica-coated nanoparticles. - Highlights: • Magnetic nanoparticles of perovskite La{sub 0.65}Sr{sub 0.35}MnO{sub 3} phase are coated with TiO{sub 2}. • The titania forms a continuous and amorphous shell and provides colloidal stability. • Morphology and surface properties are compared to a silica-coated product. • MRI properties of both the titania- and silica-coated particles are studied at 0.5 T. • The temperature dependence of r{sub 2} is strongly affected by the type of coating.

  4. Hydrothermal and postsynthesis surface modification of cubic, MCM-48, and ultralarge pore SBA-15 mesoporous silica with titanium

    Energy Technology Data Exchange (ETDEWEB)

    Morey, M.S.; O' Brien, S.; Schwarz, S.; Stucky, G.D.

    2000-04-01

    The authors describe the introduction of titanium centers to cubic MCM-48 was hydrothermally prepared with a gemini surfactant that favors the cubic phase and leads to a high degree of long-range pore ordering. This phase was chosen due to its high surface area (1100--1300 m{sup 2}/g) and its three-dimensional, bicontinuous pore array. SBA-15, synthesized with a block copolymer template under acidic conditions, has a surface area from 600 to 900 m{sup 2}/g and an average pore diameter of 69 {angstrom}, compared to 24--27 {angstrom} for MCM-48. Alkoxide precursors of titanium were used to prepare samples of Ti-MCM-48 and Ti-SBA-15. The authors have detailed the bulk and molecular structure of both the silica framework and the local bonding environment of the titanium ions within each matrix. X-ray powder diffraction and nitrogen adsorption shows the pore structure is maintained despite some shrinkage of the pore diameter at high Ti loadings by grafting methods. UV-visible and Raman spectroscopy indicate that grafting produces the least amount of Ti-O-Ti bonds and instead favors isolated tetrahedral and octahedral titanium centers. High-resolution photoacoustic FTIR spectra demonstrated the presence of intermediate range order within the silicate walls of MCM-48, established the consumption of surface silanols to form Si-O-Ti bonds by grafting, and resolved the characteristic IR absorbance at 960 cm{sup {minus}1}, occurring in titanium silicates, into two components. All three spectroscopic techniques, including in situ Raman, reveal the reactive intermediates formed when the materials are contacted with hydrogen peroxide.

  5. An overview of the fundamentals of the chemistry of silica with relevance to biosilicification and technological advances.

    Science.gov (United States)

    Belton, David J; Deschaume, Olivier; Perry, Carole C

    2012-05-01

    Biomineral formation is widespread in nature, and occurs in bacteria, single-celled protists, plants, invertebrates, and vertebrates. Minerals formed in the biological environment often show unusual physical properties (e.g. strength, degree of hydration) and often have structures that exhibit order on many length scales. Biosilica, found in single-celled organisms through to higher plants and primitive animals (sponges), is formed from an environment that is undersaturated with respect to silicon, and under conditions of approximately neutral pH and relatively low temperatures of 4-40 °C compared to those used industrially. Formation of the mineral may occur intracellularly or extracellularly, and specific biochemical locations for mineral deposition that include lipids, proteins and carbohydrates are known. In most cases, the formation of the mineral phase is linked to cellular processes, an understanding of which could lead to the design of new materials for biomedical, optical and other applications. In this contribution, we describe the aqueous chemistry of silica, from uncondensed monomers through to colloidal particles and 3D structures, that is relevant to the environment from which the biomineral forms. We then describe the chemistry of silica formation from alkoxides such as tetraethoxysilane, as this and other silanes have been used to study the chemistry of silica formation using silicatein, and such precursors are often used in the preparation of silicas for technological applications. The focus of this article is on the methods, experimental and computational, by which the process of silica formation can be studied, with an emphasis on speciation. © 2012 The Authors Journal compilation © 2012 FEBS.

  6. Enhancement of seeding for electroless Cu plating of metallic barrier layers by using alkyl self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Sung-Te [Department of Electronic Engineering, Hsiuping University of Science and Technology, Dali 412, Taichung, Taiwan (China); Chung, Yu-Cheng [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Fang, Jau-Shiung [Department of Materials Science and Engineering, National Formosa University, Huwei 632, Taiwan (China); Cheng, Yi-Lung [Department of Electrical Engineering, National Chi-Nan University, Puli, Nantou 545, Taiwan (China); Chen, Giin-Shan, E-mail: gschen@fcu.edu.tw [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China)

    2017-05-31

    Highlights: • Ta barrier layers are used as model substrates for seeding of electroless plating. • Ta layers seeded with Ta-OH yield seeds with limited density and large size (>10 nm). • Substantial improvement of seeding is obtained with functionalized SAMs. • The mechanism of seeding improvement by functionalized SAMs is clearly clarified. - Abstract: Tethering a self-assembled monolayer (SAM) on ultralow-k (porous) dielectric materials as a seed-trapping layer for electroless Cu plating has been extensively studied. By contrast, literature on direct electroless Cu plating of metallic barrier layers assisted by SAMs is scarce. Therefore, Ta, a crucial component of barrier materials for Cu interconnect metallization, was investigated as a model substrate for a new seeding (Ni catalyst formation) process of electroless Cu plating. Transmission and scanning electron microscopies indicated that catalytic particles formed on Ta films through Ta−OH groups tend to become aggregates with an average size of 14 nm and density of 2 × 10{sup 15} m{sup −2}. By contrast, Ta films with a plasma-functionalized SAM tightly bound catalytic particles without agglomeration, thus yielding a markedly smaller size (3 nm) and higher density (3 × 10{sup 16} m{sup −2}; one order greater than those formed by other novel methods). X-ray photoelectron spectroscopy clearly identified the types of material species and functional groups induced at each step of the seeding process. Moreover, the phase of the catalytic particles, either nickel alkoxide, Ni(OH){sub 2}, or metallic Ni, along with the seed-bonding mechanism, was also unambiguously distinguished. The enhancement of film-formation quality of Cu by the new seeding process was thus demonstrated.

  7. Synthesis and characterization of Sn doped TiO{sub 2} photocatalysts: Effect of Sn concentration on the textural properties and on the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Vázquez, I.; Del Angel, G.; Bertin, V. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); González, F. [Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Vázquez-Zavala, A.; Arrieta, A. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Padilla, J.M. [Universidad Tecnológica del Centro de Veracruz, Área de Tecnología, Av. Universidad Carretera Federal Cuitláhuac-La Tinaja No. 350, Cuitláhuac, Veracruz 94910 (Mexico); Barrera, A. [Universidad de Guadalajara, Centro Universitario de la Ciénega, Av. Universidad, Número 1115, Col. Linda Vista, Apdo. Postal 106, Ocotlán Jal. (Mexico); Ramos-Ramirez, E. [Departamento de Química, División de Ciencias Naturales y Exactas, Campus Guanajuato de la Universidad de Guanajuato Noria Alta S/N, Col. Noria Alta, Guanajuato, Gto. C.P. 36050 (Mexico)

    2015-09-15

    Abstract: TiO{sub 2} and Sn-doped TiO{sub 2} materials were prepared by sol–gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA–DSC), X-ray Rietveld refinement, N{sub 2} adsorption (BET), transmission electron microscopy (TEM), UV–vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO{sub 2}, whereas anatase and brookite were obtained in Sn-doped TiO{sub 2} samples. Sn dopant acts as a promoter in phase transformation of TiO{sub 2}. The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn{sup 4+} into the anatase TiO{sub 2} structure. Sn{sup 4+} inhibits the growth of TiO{sub 2} crystallite size, which leads to an increase of the specific surface area of TiO{sub 2}. From XRD analysis, the solid solution limit of Sn{sup 4+} into TiO{sub 2} is 5 mol% Sn. The photocatalytic activity on Sn{sup 4+} doped TiO{sub 2} was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size.

  8. Comparative Study of the Optical and Textural Properties of Tetrapyrrole Macrocycles Trapped Within ZrO2, TiO2, and SiO2 Translucent Xerogels

    Directory of Open Access Journals (Sweden)

    Eduardo Salas-Bañales

    2015-10-01

    Full Text Available The entrapping of physicochemical active molecules inside mesoporous networks is an appealing field of research due to the myriad of potential applications in optics, photocatalysis, chemical sensing, and medicine. One of the most important reasons for this success is the possibility of optimizing the properties that a free active species displays in solution but now trapped inside a solid substrate. Additionally it is possible to modulate the textural characteristics of substrates, such as pore size, specific surface area, polarity and chemical affinity of the surface, toward the physical or chemical adhesion of a variety of adsorbates. In the present document, two kinds of non-silicon metal alkoxides, Zr and Ti, are employed to prepare xerogels containing entrapped tetrapyrrolic species that could be inserted beforehand in analogue silica systems. The main goal is to develop efficient methods for trapping or binding tetrapyrrole macrocycles inside TiO2 and ZrO2 xerogels, while comparing the properties of these systems against those of the SiO2 analogues. Once the optimal synthesis conditions for obtaining translucent monolithic xerogels of ZrO2 and TiO2 networks were determined, it was confirmed that these substrates allowed the entrapment, in monomeric form, of macrocycles that commonly appear as aggregates within the SiO2 network. From these experiments, it could be determined that the average pore diameters, specific surface areas, and water sorption capacities depicted by each one of these substrates, are a consequence of their own nature combined with the particular structure of the entrapped tetrapyrrole macrocycle. Furthermore, the establishment of covalent bonds between the intruding species and the pore walls leads to the obtainment of very similar pore sizes in the three different metal oxide (Ti, Zr, and Si substrates as a consequence of the templating effect of the encapsulated species.

  9. Synthesis of heterobimetallic Ru-Mn complexes and the coupling reactions of epoxides with carbon dioxide catalyzed by these complexes.

    Science.gov (United States)

    Man, Man Lok; Lam, King Chung; Sit, Wing Nga; Ng, Siu Man; Zhou, Zhongyuan; Lin, Zhenyang; Lau, Chak Po

    2006-01-23

    The heterobimetallic complexes [(eta5-C5H5)Ru(CO)(mu-dppm)Mn(CO)4] and [(eta5-C5Me5)Ru(mu-dppm)(mu-CO)2Mn(CO)3] (dppm = bis-diphenylphosphinomethane) have been prepared by reacting the hydridic complexes [(eta5-C5H5)Ru(dppm)H] and [(eta5-C5Me5)Ru(dppm)H], respectively, with the protonic [HMn(CO)5] complex. The bimetallic complexes can also be synthesized through metathetical reactions between [(eta5-C5R5)Ru(dppm)Cl] (R = H or Me) and Li+[Mn(CO)5]-. Although the complexes fail to catalyze the hydrogenation of CO2 to formic acid, they catalyze the coupling reactions of epoxides with carbon dioxide to yield cyclic carbonates. Two possible reaction pathways for the coupling reactions have been proposed. Both routes begin with heterolytic cleavage of the RuMn bond and coordination of an epoxide molecule to the Lewis acidic ruthenium center. In Route I, the Lewis basic manganese center activates the CO2 by forming the metallocarboxylate anion which then ring-opens the epoxide; subsequent ring-closure gives the cyclic carbonate. In Route II, the nucleophilic manganese center ring-opens the ruthenium-attached epoxide to afford an alkoxide intermediate; CO2 insertion into the RuO bond followed by ring-closure yields the product. Density functional calculations at the B3LYP level of theory were carried out to understand the structural and energetic aspects of the two possible reaction pathways. The results of the calculations indicate that Route II is favored over Route I.

  10. Rationalization of the pKa values of alcohols and thiols using atomic charge descriptors and its application to the prediction of amino acid pKa's.

    Science.gov (United States)

    Ugur, Ilke; Marion, Antoine; Parant, Stéphane; Jensen, Jan H; Monard, Gerald

    2014-08-25

    In a first step toward the development of an efficient and accurate protocol to estimate amino acids' pKa's in proteins, we present in this work how to reproduce the pKa's of alcohol and thiol based residues (namely tyrosine, serine, and cysteine) in aqueous solution from the knowledge of the experimental pKa's of phenols, alcohols, and thiols. Our protocol is based on the linear relationship between computed atomic charges of the anionic form of the molecules (being either phenolates, alkoxides, or thiolates) and their respective experimental pKa values. It is tested with different environment approaches (gas phase or continuum solvent-based approaches), with five distinct atomic charge models (Mulliken, Löwdin, NPA, Merz-Kollman, and CHelpG), and with nine different DFT functionals combined with 16 different basis sets. Moreover, the capability of semiempirical methods (AM1, RM1, PM3, and PM6) to also predict pKa's of thiols, phenols, and alcohols is analyzed. From our benchmarks, the best combination to reproduce experimental pKa's is to compute NPA atomic charge using the CPCM model at the B3LYP/3-21G and M062X/6-311G levels for alcohols (R(2) = 0.995) and thiols (R(2) = 0.986), respectively. The applicability of the suggested protocol is tested with tyrosine and cysteine amino acids, and precise pKa predictions are obtained. The stability of the amino acid pKa's with respect to geometrical changes is also tested by MM-MD and DFT-MD calculations. Considering its strong accuracy and its high computational efficiency, these pKa prediction calculations using atomic charges indicate a promising method for predicting amino acids' pKa in a protein environment.

  11. Functionalization of luminescent YVO{sub 4}:Eu{sup 3+} nanoparticles by sol–gel

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Barbara A.; Ferreira, Natália H.; Oliveira, Pollyanna F.; Faria, Emerson H. de; Tavares, Denise C.; Rocha, Lucas A.; Ciuffi, Katia J.; Nassar, Eduardo J., E-mail: eduardo.nassar@unifran.edu.br

    2015-03-15

    Over the last decades, researchers have explored nanotechnological applications in different areas. The non-hydrolytic and hydrolytic sol–gel routes offer the ideal conditions to obtain materials with distinct compositions and multifunctionality, for use in such diverse areas as nanomedicine and technology. In this work, we used the modified hydrolytic sol–gel route to prepare YVO{sub 4} doped with Eu{sup 3+} ion. The YVO{sub 4}:Eu{sup 3+} nanoparticles were functionalized with 3-chloropropyltriethoxysilane using the hydrolytic sol–gel process; the drug cisplatin was then added to them. The final powder was characterized by thermal analysis, infrared spectroscopy, X-ray diffraction, and photoluminescence. The powder X-ray diffraction patterns of the samples obtained before and after functionalization revealed well defined peaks ascribed to the tetragonal structure of the YVO{sub 4} phase. The thermal analysis curves evidenced mass loss relative to 3-chloropropyltriethoxysilane and cisplatin decomposition. Infrared spectroscopy showed the peaks related to the CH and NH groups vibration modes, confirming YVO{sub 4} functionalization. The excitation and emission spectrum of the Eu{sup 3+} ion did not change upon its doping into the matrix functionalized with 3-chloropropyl and cisplatin. Cytotoxicity tests conducted on normal Chinese hamster (V79 cells) and murine melanoma (B16F10) cells attested that the matrix was not toxic. - Highlights: • Sol–gel methodology was used to obtain luminescent YVO{sub 4}. • Matrix was functionalized by alkoxide. • YVO{sub 4} matrix was not toxic. • YVO{sub 4}:Eu{sup 3+} nanoparticles existed in the cell cytoplasm and nucleus. • YVO{sub 4}:Eu{sup 3+} can function as a fluorescent label and drug delivery system.

  12. Optimal Surface Amino-Functionalization Following Thermo-Alkaline Treatment of Nanostructured Silica Adsorbents for Enhanced CO2 Adsorption

    Directory of Open Access Journals (Sweden)

    Obdulia Medina-Juárez

    2016-11-01

    Full Text Available Special preparation of Santa Barbara Amorphous (SBA-15, mesoporous silica with highly hexagonal ordered, these materials have been carried out for creating adsorbents exhibiting an enhanced and partially selective adsorption toward CO2. This creation starts from an adequate conditioning of the silica surface, via a thermo-alkaline treatment to increase the population of silanol species on it. CO2 adsorption is only reasonably achieved when the SiO2 surface becomes aminated after put in contact with a solution of an amino alkoxide compound in the right solvent. Unfunctionalized and amine-functionalized substrates were characterized through X-ray diffraction, N2 sorption, Raman spectroscopy, electron microscopy, 29Si solid-state Nuclear Magnetic Resonance (NMR, and NH3 thermal programmed desorption. These analyses proved that the thermo-alkaline procedure desilicates the substrate and eliminates the micropores (without affecting the SBA-15 capillaries, present in the original solid. NMR analysis confirms that the hydroxylated solid anchors more amino functionalizing molecules than the unhydroxylated material. The SBA-15 sample subjected to hydroxylation and amino-functionalization displays a high enthalpy of interaction, a reason why this solid is suitable for a strong deposition of CO2 but with the possibility of observing a low-pressure hysteresis phenomenon. Contrastingly, CH4 adsorption on amino-functionalized, hydroxylated SBA-15 substrates becomes almost five times lower than the CO2 one, thus giving proof of their selectivity toward CO2. Although the amount of retained CO2 is not yet similar to or higher than those determined in other investigations, the methodology herein described is still susceptible to optimization.

  13. Titanium (IV) sol-gel chemistry in varied gravity environments

    Science.gov (United States)

    Hales, Matthew; Martens, Wayde; Steinberg, Theodore

    Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time

  14. Methane dry reforming catalysts for the production of hydrogen and carbon monoxide

    International Nuclear Information System (INIS)

    Iriarte, M; Becerra, A; Castro Luna, A

    2005-01-01

    The reaction of carbon dioxide reforming of methane (dry reforming) is a very attractive way to convert low-cost reactants in synthesis gas (CO + H 2 ).Moreover, the reaction also has very important environmental effects because both methane and carbon dioxide are greenhouse gases, and may become valuable raw materials. One of the advantages of the dry reforming compared with the conventional steam reforming is the low H 2 :CO relationship in the product, which is preferred for the synthesis of oxoalcohols and oxygenated compounds. Although noble metals based catalysts have been proved to be less sensitive to coke, the high cost and restricted availability limit their use in this process.From an industrial standpoint, it is more desirable to develop nickel-based catalysts, which are resistant to carbon deposition and exhibit stable operation for extended periods of time.In this work nickel-alumina catalysts, pure or promoted with rhodium or ruthenium, were prepared using different techniques, employing aluminum and nickel alkoxides, and characterized and selected according to their catalytic activity and coking resistance.These catalysts are to be used in an inert ceramic membrane reactor.The nickel precursor is a nickel alkoxide incorporated to the matrix precursor of alumina, which at the same time is an aluminum alkoxide.Under this scheme, catalysts with a 14% nickel charge were prepared using three preparation methods: pC0: characteristics: hydrolysis and acid peptization with HNO 3 . A1C0: characteristics: thermal decomposition. A1C0H: characteristics: thermal decomposition and subsequent hydrothermal treatment.To sum up, three Ni-A1 2 O 3 catalysts, three Ni-Rh-A1 2 O 3 catalysts, and three Ni-Ru-A1 2 O 3 catalysts were prepared.Each catalyst was prepared using the three methods: pC0-Ni-X, A1C0-Ni-X, and A1C0H-Ni-X, (X= Ru or Rh).The precursors of alumina and nickel were aluminum sec-butoxide and nickel 1-methoxide-2-propoxide. Microstructure characterization

  15. Influence of Irradiance, Flow Rate, Reactor Geometry, and Photopromoter Concentration in Mineralization Kinetics of Methane in Air and in Aqueous Solutions by Photocatalytic Membranes Immobilizing Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    Ignazio Renato Bellobono

    2008-01-01

    Full Text Available Photomineralization of methane in air (10.0–1000 ppm (mass/volume of C at 100% relative humidity (dioxygen as oxygen donor was systematically studied at 318±3 K in an annular laboratory-scale reactor by photocatalytic membranes immobilizing titanium dioxide as a function of substrate concentration, absorbed power per unit length of membrane, reactor geometry, and concentration of a proprietary vanadium alkoxide as photopromoter. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC disappearance, to yield carbon dioxide, were followed. At a fixed value of irradiance (0.30 W⋅cm-1, the mineralization experiments in gaseous phase were repeated as a function of flow rate (4–400 m3⋅h−1. Moreover, at a standard flow rate of 300 m3⋅h−1, the ratio between the overall reaction volume and the length of the membrane was varied, substantially by varying the volume of reservoir, from and to which circulation of gaseous stream took place. Photomineralization of methane in aqueous solutions was also studied, in the same annular reactor and in the same conditions, but in a concentration range of 0.8–2.0 ppm of C, and by using stoichiometric hydrogen peroxide as an oxygen donor. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters, k1 and K1, k2 and K2, were calculated, which is able to fit the whole kinetic profile adequately. The influence of irradiance on k1 and k2, as well as of flow rate on K1 and K2, is rationalized. The influence of reactor geometry on k values is discussed in view of standardization procedures of photocatalytic experiments. Modeling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photopromoter, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or

  16. Titanium dioxide thin films deposited by the sol-gel technique starting from titanium oxy-acetyl acetonate: gas sensing and photocatalyst applications

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, A.; Mayen-Hernandez, S.A.; L. Olvera, M. de la [Departamento de Ingenieria Electrica-SEES, Centro de Investigacion y de Estudios Avanzados del IPN, CINVESTAV-IPN, Mexico (Mexico); Tirado-Guerra, S. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, Mexico (Mexico)

    2010-09-15

    Titanium dioxide (TiO{sub 2}) thin films were deposited onto sodocalcic glass plates by the sol-gel technique, starting from a non-alkoxide route, namely, titanium oxy-acetyl acetonate as Ti precursor. Film thickness effect on both the gas sensing and photocatalytic degradation performance was studied. The as-deposited films were annealed in air at 400 C. All the X-ray spectra of the films show a very broad-peak centered in a 2{theta} angle around 30 . In the case of the thinnest films the surface morphology is uniform and very smooth, whereas for the thickest films the corresponding surface is covered by grains with a rod-like shape with a length on the order of 140 nm. The films were tested both for two straightforward applications: ultraviolet assisted-degradation of methylene blue dissolved in water, at different times, as well as gas sensor in a controlled propane (C{sub 3}H{sub 8}) atmosphere. As the film thickness increases, the degradation of methylene blue (MB) also increases. The thickest TiO{sub 2} thin films after being exposed by 5 hours to the catalytic degradation, promoted by ultraviolet illumination, showed a final MB solution degradation in the order of 48%. This result can be associated with the increase in the effective exposed area of the TiO{sub 2} thin films. On the other hand, the exposition of the films to a controlled propane atmosphere produced a significant change in the surface electrical resistance of the films at operating temperatures of 200 C and above. In fact, in the case of the thickest TiO{sub 2} films, a dramatic electrical resistance change of non-exposed and propane exposed - 560 to 0.7 M{omega} -, was registered. The results show that TiO{sub 2} films deposited by an economical deposition technique, as is the case of the sol-gel technique, could have an important potential in industrial applications. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. A new sol–gel synthesis of 45S5 bioactive glass using an organic acid as catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Faure, J., E-mail: joel.faure@univ-reims.fr [Université de Reims Champagne-Ardenne, Laboratoire Ingénierie et Sciences des Matériaux, LISM EA 4695, 21 rue Clément ADER, 51685 REIMS Cedex 2 (France); Drevet, R., E-mail: richard.drevet@univ-reims.fr [Université de Reims Champagne-Ardenne, Laboratoire Ingénierie et Sciences des Matériaux, LISM EA 4695, 21 rue Clément ADER, 51685 REIMS Cedex 2 (France); Lemelle, A.; Ben Jaber, N.; Tara, A. [Université de Reims Champagne-Ardenne, Laboratoire Ingénierie et Sciences des Matériaux, LISM EA 4695, 21 rue Clément ADER, 51685 REIMS Cedex 2 (France); El Btaouri, H. [Université de Reims Champagne-Ardenne UMR CNRS MEDyC, EA 7369, Campus Moulin de la Housse, 51687 REIMS Cedex 2 (France); Benhayoune, H. [Université de Reims Champagne-Ardenne, Laboratoire Ingénierie et Sciences des Matériaux, LISM EA 4695, 21 rue Clément ADER, 51685 REIMS Cedex 2 (France)

    2015-02-01

    In this paper a new sol–gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol–gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol–gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2 M nitric acid solution or either a 5 mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer–Emmett–Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol–gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4 h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol–gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol–gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol–gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. - Highlights: • Citric acid is employed as a catalyzer of the sol–gel process. • This catalyzer is used at a very low concentration for the hydrolysis reaction. • The chemical composition of the bioglass synthesized by the sol–gel process is optimized. • The properties of two sol–gel bioglasses are compared with those of the commercial

  18. Fabrication of ceramic layer-by-layer infrared wavelength photonic band gap crystals

    Science.gov (United States)

    Kang, Henry Hao-Chuan

    Photonic band gap (PBG) crystals, also known as photonic crystals, are periodic dielectric structures which form a photonic band gap that prohibit the propagation of electromagnetic (EM) waves of certain frequencies at any incident angles. Photonic crystals have several potential applications including zero-threshold semiconductor lasers, the inhibiting spontaneous emission, dielectric mirrors, and wavelength filters. If defect states are introduced in the crystals, light can be guided from one location to another or even a sharp bending of light in submicron scale can be achieved. This generates the potential for optical waveguide and optical circuits, which will contribute to the improvement in the fiber-optic communications and the development of high-speed computers. The goal of this dissertation research is to explore techniques for fabricating 3D ceramic layer-by-layer (LBL) photonic crystals operating in the infrared frequency range, and to characterize the infilling materials properties that affect the fabrication process as well as the structural and optical properties of the crystals. While various approaches have been reported in literature for the fabrication of LBL structure, the uniqueness of this work ties with its cost-efficiency and relatively short process span. Besides, very few works have been reported on fabricating ceramic LBL crystals at mid-IR frequency range so far. The fabrication techniques reported here are mainly based on the concepts of microtransfer molding with the use of polydimethyl siloxane (PDMS) as molds/stamps. The infilling materials studied include titanium alkoxide precursors and aqueous suspensions of nanosize titania particles (slurries). Various infilling materials were synthesized to determine viscosities, effects on drying and firing shrinkages, effects on film surface roughness, and their moldability. Crystallization and phase transformation of the materials were also monitored using DTA, TGA and XRD. Mutilayer crystal

  19. Synthesis, characterization and single crystal structures of chiral Schiff base and its tetranuclear palladium complex with Pdsbnd Osbnd Pd bridging and Pdsbnd Pd bonds

    Science.gov (United States)

    Rajegowda, H. R.; Kumar, P. Raghavendra; Hosamani, Amar; Butcher, R. J.; Naveen, S.; Lokanath, N. K.

    2018-03-01

    A new chiral Schiff base ligand 2-{N-[(2S)-(1-hydroxy-3-phenylpropan-2-yl]ethanimidoyl} phenol ((S)sbnd H2L) was obtained by acid catalyzed condensation of (2S)-(-)-2-amino-3-phenyl-1-propanol with 2‧-hydroxyacetophenone. The palladium complex was prepared by treating a solution of (S)sbnd H2L in acetone with a solution of Na2PdCl4 in water in 1:1 M ratio. The new ligand and its complex were characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy, polarimetry and elemental analysis and their molecular structures were determined by single crystal X-ray diffraction. Both the compounds crystallizes in monoclinic system in the space group P21. There exists an intra [Osbnd H ⋯N (1.62(5) Å)] and intermolecular [Osbnd H ⋯O (1.53(5) Å) and Csbnd H ⋯O (2.59 Å)] hydrogen bonding and secondary interactions in the crystal of (S)sbnd H2L. The structure of the palladium complex was found very interesting wherein the ligand coordinated to metal center as tridentate dianionic (O-, N, O-) fashion, (S)-L, resulting in a tetranuclear palladium cluster, [Pd4((S)-L)4]. In these supramolecular structures phenolate oxygen coordinated to Pd(II) ion as Pdsbnd O terminal bonds [1.934(12) - 1.977(11) Å] and the alkoxide oxygen coordinated as Pdsbnd Osbnd Pd bridging bonds [1.993(11) - 2.012(12) Å]. The Pdsbnd N bond lengths found were in the range of 1.949(13) to 1.919(12) Å. There exists two asymmetric tetranuclear complex molecules in its crystal lattice. There exists very strong metal-metal bond interaction, Pd(2)sbnd Pd(3) [3.0410(18) Å] and Pd(6)sbnd Pd(7) [3.0517(19) Å] respectively in the two asymmetric units.

  20. Probing the mer- to fac-isomerization of tris-cyclometallated homo- and heteroleptic (C,N)3 iridium(III) complexes.

    Science.gov (United States)

    McDonald, Aidan R; Lutz, Martin; von Chrzanowski, Lars S; van Klink, Gerard P M; Spek, Anthony L; van Koten, Gerard

    2008-08-04

    We have developed techniques which allow for covalent tethering, via a "hetero" cyclometallating ligand, of heteroleptic tris-cyclometallated iridium(III) complexes to polymeric supports (for application in light-emitting diode technologies). This involved the selective synthesis and thorough characterization of heteroleptic [Ir(C,N) 2(C',N')] tris-cyclometallated iridium(III) complexes. Furthermore, the synthesis and characterization of heteroleptic [Ir(C,N) 2OR] complexes is presented. Under standard thermal conditions for the synthesis of the facial ( fac) isomer of tris-cyclometallated complexes, it was not possible to synthesize pure heteroleptic complexes of the form [Ir(C,N) 2(C',N')]. Instead, a mixture of homo- and heteroleptic complexes was acquired. It was found that a stepwise procedure involving the synthesis of a pure meridonial ( mer) isomer followed by photochemical isomerization of this mer to the fac isomer was necessary to synthesize pure fac-[Ir(C,N) 2(C',N')] complexes. Under thermal isomerization conditions, the conversion of mer-[Ir(C,N) 2(C',N')] to fac-[Ir(C,N) 2(C',N')] was also not a clean reaction, with again a mixture of homo- and heteroleptic complexes acquired. An investigation into the thermal mer to fac isomerization of both homo- and heteroleptic tris-cyclometallated complexes is presented. It was found that the process is an alcohol-catalyzed reaction with the formation of an iridium alkoxide [Ir(C,N) 2OR] intermediate in the isomerization process. This catalyzed reaction can be carried out between 50 and 100 degrees C, the first such example of low-temperature mer-fac thermal isomerization. We have synthesized analogous complexes and have shown that they do indeed react so as to give fac-tris-cyclometallated products. A detailed explanation of the intermediates (and all of their stereoisomers, in particular when systems of the generic formula [M(a,b) 2(a',b')] are synthesized) formed in the mer to fac isomerization process is

  1. Surface modification, organometallic and polyaryl polymer coatings, and flame spray technologies for preventing corrosion of metals. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T.

    1995-07-01

    To improve adherent properties of electrogalvanized steel (EGS) to polymeric topcoats, the surfaces of EGS were modified by polyelectrolyte-modified zinc phosphating solution. The electrochemical reaction between phosphating solution and EGS led to the complete coverage with fully grown hopeite crystals after only 5 sec treatment, thereby improving adhesion to topcoating and providing protection of EGS against corrosion. To evaluate the ability of polyphenylene sulfide (PPS) polyaryl thermoplastic coatings to protect zinc phosphate (Zn{center_dot}Ph)treated steels from corrosion in a wet, harsh environment ( 1.0 wt % H{sub 2}SO{sub 4}, 3.0 wt % NaCl and 96.0 wt % water at temperatures from 25{degrees} to 200{degree}C), we exposed them in an autoclave to attempt heating-cooling cyclic fatigue tests (1 cycle = 12 hr at 200{degrees}C + 12 hr at 25{degrees}C) up to 90 times. The major chemical reaction at the interface between the PPS and Zn in the Zn-Ph layer during cycling led to the formation of ZnS reaction product, which enhanced the Zn-Ph-to-PPS adhesive bond; correspondingly, there were no signs of peeling and separation of the coating after 90 cycles. organometallosiloxane polymer (OMSP) was synthesized through the hydrolysis-condensation reaction of the mixed precursor solutions of the N-[3-(triethoxysily)propyl]-4,5,-dihydroimidazole and {Beta}-trimethoxysilylethyl-2-pyridine sols in liquor medium and the metal alkoxides and metallocene dichloride dissolved in water or tetrahydrofurane. The OMSP films (thickness, 0. 5 to 1. 0 {mu}m) deposited by simple dip-withdrawing coating methods to aluminum alloys displayed the impedance of > 10{sup 6} ohm-cm {sup 2} after exposure for 40 days in 0.5 N NaCl solution at 25{degrees}C and the 3000 hr-salt spray resistance. Using a flame spray coating process, the methacrylic acid-modified polyethylene copolymer was overlaid onto cold rolled steel surfaces.

  2. Protective performances of two anti-graffiti treatments towards sulfite and sulfate formation in SO 2 polluted model environment

    Science.gov (United States)

    Carmona-Quiroga, Paula María; Panas, Itai; Svensson, Jan-Erik; Johansson, Lars-Gunnar; Blanco-Varela, María Teresa; Martínez-Ramírez, Sagrario

    2010-11-01

    Specific strategies for protection are being developed to counter both the staining and corrosive effects of polluted air in cities, as well as to allow for efficient removal of unwanted graffiti paintings. These protection strategies employ molecules with tailored functionalities, e.g. being hydrophobic, while maintaining porosity for molecular water vapour permeation. The present study employs SO 2 and water to probe the behaviors of two anti-graffiti treatments, a water-base fluoroalkylsiloxane ("Protectosil Antigraffiti" marketed by Degussa) and an organically modified silicate (Ormosil) synthesized from a polymer chain (polydimethyl siloxane, PDMS) and two network forming alkoxides (Zr propoxide and methyl triethoxy silane, MTES) dissolved in n-propanol, on five building materials, comprising limestone, aged lime mortar, hydrated cement mortar, granite, and brick material. The materials were exposed to a synthetic atmosphere for 20 h in a climate chamber, 0.78 ± 0.03 ppm of SO 2 and 95% RH. Diffuse reflectance Fourier transform infrared (DR-FTIR) spectra were registered before and after exposure in the climate chamber in the cases of both treated and untreated samples. DR-FTIR, scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) analyses, suggest the anti-graffiti Ormosil to suppress formation of calcium sulfite hemihydrate (the primary initial product of the reaction of calcium compounds with SO 2 and water) on carbonate materials (limestone and lime mortar). In case of the granite, brick and cement mortar, Ormosil has a negligible influence on the SO 2 capture. While no sulfite formation was detected by DR-FTIR, gypsum is inferred to form due to metal oxides and minority compounds catalysed oxidation of sulfite to sulfate. In case of brick, this understanding finds support from SEM images as well as EDX. A priori presence of gypsum in hydrated cement mortars prevents positive identification by SEM. However, support for sulfur

  3. Experimental and theoretical studies of hydrolysis of nerve agent sarin by binuclear zinc biomimetic catalysts

    Science.gov (United States)

    Guo, Nan; Zhong, Jin-Yi; Chen, Shi-Lu; Liu, Jing-Quan; Min, Qi; Shi, Rui-Xue

    2015-08-01

    A complex (ZnL1) of 2,2-(2-hydroxy-5-methyl-1,3-phenylene)bis(methylene)bis ((pyridin-2-ylmethyl)azanediyl)diethanol (this ligand is named by L1) functionalized with two Zn(II) centers, has been previously suggested to be a structural model for binuclear zinc phosphotriesterases (PTEs) and proven to be an effective catalyst for the hydrolysis of bis(2,4-dinitrophenyl)phosphate (BDNPP). In this paper, ZnL1 was further found to have a high catalytic activity for the hydrolysis of isopropyl methylphosphonofluoridate (sarin, GB) with kcat/Km = 0.051 s-1 M-1 at 303 K, examined by on-site NMR analysis. The subsequent density functional theory (DFT) calculations indicate that a terminal alkoxide (Ot) bound by Zn may work as a general base to activate a water molecule and then a hydroxide derived from the latter performs the initial nucleophilic attack on the phosphor in GB. Inspired by this mechanism, a new biomimetic catalyst was designed and synthesized by replacing the two pyridines of ZnL1 by hydroxyls, i.e. a complex of two Zn(II) with 2,6-bis((bis(2-hydroxyethyl)amino)methyl)-4-methylphenol (the ligand is named by L2). This replacement was expected to increase the Ot basicity, thereby facilitating the nucleophilic attack and the overall hydrolysis of GB. It was shown that ZnL2 had a very high catalytic efficiency for the hydrolysis of GB, with kcat/Km = 0.11 s-1 M-1 at 303 K and about 90% conversion in 30 min. The following DFT calculations proposed a detailed reaction mechanism of ZnL2 and gave an energy barrier (5.8 kcal M-1) very close to the experimental activation energy (5.6 kcal M-1). In this study, a mechanism-inspired design strategy has been demonstrated to be successful in developing biomimetic catalyst.

  4. Estudio por espectroscopía infrarroja de la reacción de obtención de geles de borosilicato con diferentes relaciones Si/B

    Directory of Open Access Journals (Sweden)

    Peña-Alonso, R.

    2005-12-01

    Full Text Available Borosilicate gels with different Si/B ratio have been prepared by the sol-gel method. Such gels were obtained by hydrolysis and further condensation of TEOS (tetraethylorthosilicate and TEB (triethylborate alkoxides in acidic aqueous media. The evolution of the Si-O-Si bonds during the sol-gel condensation was dependent on the concentration of boron. Infrared spectroscopy suggested that boron plays an important role on the formation of the siloxane bonds from the hydrolysed TEOS. Thus, the cross-linking of Si-O-Si bonds decreased and the condensation of linear structures increased when the amount of TEB was higher than 10 wt.%. Moreover, it has been observed that this behaviour is directly related with the increase of gelling time in the sols containing significant amount of boron.

    Se ha llevado a cabo el estudio de la formación de diferentes geles de borosilicato preparados mediante la reacción sol-gel de hidrólisis y condensación de los alcóxidos TEOS (tetraetilortosilicato y TEB (trietilborato en diferentes proporciones Si/B y en medio acuoso acidulado. La formación de los enlaces Si-O-Si que tiene lugar durante la condensación la reacción sol-gel depende de la cantidad de boro añadido a los diferentes soles. Así, la espectroscopia infrarroja ha puesto de manifiesto que el boro juega un papel determinante en la formación de los enlaces siloxano a partir del TEOS hidrolizado, observándose que el entrecruzamiento de los enlaces Si-O-Si disminuye con el empleo de cantidades de TEB superiores al 10% en peso a la vez que aumenta la condensación en forma de estructuras lineales de los mismos. Además, se pone de manifiesto que este comportamiento está relacionado con el aumento de los tiempos de gelificación observados para altas adiciones de boro.

  5. Modificación química del precursor de titanio para obtener soles estables de silice – titania: Uso de acetilacetona

    Directory of Open Access Journals (Sweden)

    Rodríguez-Páez, J. E.

    2004-02-01

    Full Text Available Sol-gel processing has become a well established technique for producing ceramic powders or glasses. This processing has been utilized to synthesize several interesting systems, e.g. the SiO2 – TiO2 system. A major concern in the stable multicomponent geles is that the hydrolysis and condensation velocities are diferent for each precursor, TEOS and Ti(OBu4 in this work. The chemical control of these reactions is currently performed by adding complexing reagents that react with metal alkoxides at a molecular level, giving rise to new molecular precursors of different structure, reactivity and functionanality. This paper shows that stable TEOS – Ti(OBu4 – H2O sol can be reproducibly prepared in the presence of acetylacetone. We shall then show that the acac behaves as a ligand, directly bonded to the titanium ion. Thus the formation of precipitate is avoided. Infra-red spectroscopy (FTIR and viscosity measures were used to demostrated this behaviour of the system.

    La técnica Sol-Gel se ha utilizado para sintetizar una serie de sistemas multicomponentes, entre ellos SiO2 – TiO2. El mayor problema en la obtención de geles multicomponentes estables es la desigual velocidad de hidrólisis y condensación que presentan los alcóxidos precursores de los cationes de interés. En este trabajo se muestra cómo adicionando acetilacetona, acacH, al sistema TEOS – Ti(OBu4 – H2O se puede obtener un sol estable. Se tomaron diferentes concentraciones de los precursores de silicio y titanio y una sola concentración de acacH. Se utilizó espectroscopia infrarroja, FTIR, para identificar los grupos funcionales presentes en el sistema y además se midió regularmente la viscosidad para determinar cualitativamente el avance de la policondensación del sistema.

  6. A new sol–gel synthesis of 45S5 bioactive glass using an organic acid as catalyst

    International Nuclear Information System (INIS)

    Faure, J.; Drevet, R.; Lemelle, A.; Ben Jaber, N.; Tara, A.; El Btaouri, H.; Benhayoune, H.

    2015-01-01

    In this paper a new sol–gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol–gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol–gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2 M nitric acid solution or either a 5 mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer–Emmett–Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol–gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4 h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol–gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol–gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol–gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. - Highlights: • Citric acid is employed as a catalyzer of the sol–gel process. • This catalyzer is used at a very low concentration for the hydrolysis reaction. • The chemical composition of the bioglass synthesized by the sol–gel process is optimized. • The properties of two sol–gel bioglasses are compared with those of the commercial

  7. Textural mesoporosity and the catalytic activity of mesoporous molecular sieves with wormhole framework structures

    International Nuclear Information System (INIS)

    Pauly, T.R.; Liu, Y.; Pinnavaia, T.J.; Billinge, S.J.L.; Rieker, T.P.

    1999-01-01

    Three different water-alcohol cosolvent systems were used to assemble mesoporous molecular sieve silicas with wormhole framework structures (previously denoted HMS silicas) from an electrically neutral amine surfactant (Sdegree) and a silicon alkoxide precursor (Idegree). The fundamental particle size and associated textural (interparticle) porosity of the disordered structures were correlated with the solubility of the surfactant in the water-alcohol cosolvents used for the SdegreeIdegree assembly process. Polar cosolvents containing relatively low volume fractions of C n H 2n+1 OH alcohols (n = 1--3) gave heterogeneous surfactant emulsions that assembled intergrown aggregates of small primary particles with high textural pore volumes (designated HMS-HTx). Conversely, three-dimensional, monolithic particles with little or no textural porosity (designated HMS-LTx) were formed from homogeneous surfactant solutions in lower polarity cosolvents. Aluminum substituted AL-HMS-HTx analogues with high textural porosity and improved framework accessibility also were shown to be much more efficient catalysts than AL-HMS-LTx or monolithic forms of hexagonal AL-MCM-41 for the sterically demanding condensed phase alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol. Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies verified the textural differences between wormhole HMS and electrostatically assembled hexagonal MCM-41 and SBA-3 molecular sieves. Power law fits to the scattering data indicated a surface fractal (D s = 2.76) for HMS-HTx, consistent with rough surfaces. A second power law at lower-q indicated the formation of a mass fractal (D m = 1.83) consistent with branching of small fundamental particles. Hexagonal MCM-41 and SBA-3 silicas, on the other hand, exhibited scattering properties consistent with moderately rough surfaces (D s = 2.35 and 2.22, respectively) and large particle diameters (much g t1 micro m). HMS-LTx silicas

  8. Layered Lepidocrocite Type Structure Isolated by Revisiting the Sol–Gel Chemistry of Anatase TiO 2 : A New Anode Material for Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jiwei [Sorbonne Universités,; Reeves, Kyle G. [Sorbonne Universités,; Porras Gutierrez, Ana-Gabriela [Sorbonne Universités,; Body, Monique [Université; Legein, Christophe [Université; Kakinuma, Katsuyoshi [Fuel; Borkiewicz, Olaf J. [X-ray; Chapman, Karena W. [X-ray; Groult, Henri [Sorbonne Universités,; Salanne, Mathieu [Sorbonne Universités,; Réseau; Dambournet, Damien [Sorbonne Universités,; Réseau

    2017-09-19

    Searches for new electrode materials for batteries must comply on financial and environmental costs to be useful in practical devices. The sol-gel chemistry has been widely used to design and implemented new concepts for the emergence of advanced materials such as hydride organic-inorganic composites. Here, we show that the simple reaction system including titanium alkoxide and water can be used to stabilize a new class of electrode materials. By investigating the crystallization path of anatase TiO2, an X-ray amorphous intermediate phase has been identified whose local structure probed by the pair distribution function, 1H solid-state NMR and DFT calculations, consists of a layered-type structure as found in the lepido-crocite. This phase presents the following general formula Ti2-xxO4-4x(OH)4x.nH2O (x ~ 0.5) where the substitution of oxide by hydroxide anions leads to the formation of titanium vacancies (•) and H2O molecules are located in interlayers. Solid-state 1H NMR has enabled to characterize three main hydroxide environments that are Ti⟂-OH, Ti22-OH and Ti3⟂-OH and layered H2O molecules. The electrochemical properties of this phase were further investigated versus lithium and is shown to be very promising with reversible capacities of around 200 mAh.g-1 and an operating voltage of 1.55 V. We further showed that the lithium intercalation proceeds via a solid-solution mechanism. 7Li solid-state NMR and DFT calculations allowed to identify lithium host sites that are located at the titanium vacancies and interlayer space with lithium being solvated by structural water molecules. The easy fabrication, the absence of lithium and easier recycling and the encouraging properties makes this class of materials very attractive for competitive electrodes for batteries. We thus demonstrate that the revisit of an “old” chemistry with

  9. Pure and Y-substituted BaZrO3 ceramics. A possible support material for fabrication of YBa2Cu3O7-x high-Tc superconductors

    International Nuclear Information System (INIS)

    Wang Xiandong.

    1993-01-01

    This thesis concerns the preparation and characterization of cuprate based high-T c superconductors (Y-123 and Bi-2223) and especially development and testing of BaZrO 3 based materials. The formation of YBa 2 Cu 3 O y (Y-123) by a CO 2 -free route involving reaction sintering of stoichiometric mixtures of chemically prepared fine powders of Y 2 BaCuO 5 , BaCuO 2 and CuO have been studied by thermal and XRD analysis. The synthesis and sintering of BaZrO 3 powders prepared by the hydroxide-alkoxide-methanol sol-gel route have been studied. The phase relations in the system BaO-Y 2 O 3 -ZrO 2 have been studied to determine the solid solubility limits for the perovskite phase Ba X Y Y Zr Z O N (X+X+Z=3) at 1500 deg. C. In the binary system Y 2 O 3 -BaZrO 3 the solubility limit was found to be ≅19 mol% Y 2 O 3 , i.e. Ba 0.81 Y 0. 4 2 Zr 0.81 O 3 . along the joint BaYO 2.5 -Ba the boundary was determined to be at BaY 0.21 Zr 0 . 79 O 2.895 . evidence for a new solid solution series between Ba 3 Y 4 O 9 and ZrO 2 are given, and a partial 1500 deg. C phase diagram for the ternary system BaO-Y 2 O 3 -ZrO 2 is presented. The growth of BaZrO 3 single crystals have been attempted both by a laser zone floating technique and flux methods. The compatibility between YBa 2 Cu 3 O 7 -X and BaZrO 3 , Ba X Y Y Zr Z O 3-δ as well as BaHfO 3 have been studied at 950 deg. and 1050 deg. C. The results show the four most promising candidates as support materials for fabrication of YBa 2 Cu 3 O y to be BaHfO 3 , BaY 0.05 Zr 0.95 O 2.975 , , BaZrO 3 and BaY 0.1 Zr 0.9 O 2.95 . (EG)

  10. Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes.

    Science.gov (United States)

    Uzelac, Marina; Borilovic, Ivana; Amores, Marco; Cadenbach, Thomas; Kennedy, Alan R; Aromí, Guillem; Hevia, Eva

    2016-03-24

    By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Low temperature sol-gel process for optical coatings based on magnesium fluoride and titanium dioxide; Niedertemperatur Sol-Gel Verfahren fuer optische Schichtsysteme auf Basis von Magnesiumfluorid und Titandioxid

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Hannes

    2009-09-24

    This work deals with the development of a low temperature sol-gel spincoating process for thin films with thicknesses in the nanometer range based on metal oxides and metal fluorides. Optical films such as anti-reflective (AR) or high reflective coatings are of much interest and consist of alternating dielectric layers of low and high refractive index materials. Regarding the general procedure for the metal fluorides a novel nonaqueous sol-gel synthesis starting from metal alkoxides and alcohol-dissolved HF was used. The coatings were dried and calcined at 100 C. The morphology of these films was characterised with REM, TEM and AFM. EDX and XPS were used to identify the chemical composition and ellipsometry and UV-vis spectroscopy to determine the optical properties of the films. This new process allows the preparation of homogeneous magnesium fluoride and titanium dioxide layers with low roughness (R{sub a} {<=} 1,9 nm) on silicon and quartz substrates. The magnesium fluoride layers are partially amorphous or microcrystalline with crystallite sizes from 2 nm to 10 nm. The titanium dioxide layers are predominantly amorphous. The thicknesses of the magnesium fluoride and titanium dioxide single layers were adjustable between 25 nm and 500 nm depending on the number of coating steps and on the concentration of the used sols. The magnesium fluoride layers had a refractive index of n{sub 500} = 1,36 and the titanium dioxide layers a refraction index of n{sub 500} = 2,05. For the first time, an alternating metal fluoride and oxide multilayer system was produced with a low temperature sol-gel method (consisting of magnesium fluoride and titanium dioxide). Based on the determined optical constants of the magnesium fluoride and titanium dioxide single layers, AR and HR multilayer systems were calculated and fabricated. The transmission spectra of the designs and the corresponding multilayer were in good agreement. Similar results were obtained with the reflection spectra

  12. Manganese/cerium clusters spanning a range of oxidation levels and CeMn(8), Ce(2)Mn(4), and Ce(6)Mn(4) nuclearities: structural, magnetic, and EPR properties.

    Science.gov (United States)

    Lampropoulos, Christos; Thuijs, Annaliese E; Mitchell, Kylie J; Abboud, Khalil A; Christou, George

    2014-07-07

    The syntheses, structures, and magnetic properties are reported for three new Ce/Mn clusters with different Ce/Mn ratios: [Ce6Mn4O12(O2CMe)10(NO3)4(py)4] (py = pyridine) (1), [CeMn8O8(O2CCH2(t)Bu)12(DMF)14] (DMF = dimethylformamide) (2), and [Ce2Mn4O2(O2CMe)6(NO3)4(hmp)4] (3; hmp(-) is the anion of 2-(hydroxymethyl)pyridine). 1 and 2 were obtained from the reaction of Ce(IV) with [Mn12O12(O2CMe)16(H2O)4] (Mn(III)8Mn(IV)4) and [Mn8O2(O2CCH2(t)Bu)14((t)BuCH2CO2H)4] (Mn(II)6Mn(III)2), respectively, whereas 3 resulted from the oxidation of Mn(II) acetate with Ce(IV) in the presence of hmpH. Cluster 1 possesses an unusual [Ce6Mn4O12](14+) core topology consisting of a [Ce6O8] face-capped octahedron, which is face-fused at each end to a [Ce(IV)2Mn(III)Mn(IV)O4] cubane. Cluster 2 possesses a nonplanar, saddlelike loop of eight Mn(III) atoms bridged by eight μ3-O(2-) ions to a central Ce(IV) atom. Cluster 3 is similar to 1 in possessing an octahedral core, but this is now a [Ce2Mn4] octahedron consisting of a Ce(III) atom on either side of a Mn4 parallelogram, with the metal atoms bridged by two μ4-O(2-) ions, the alkoxide arms of four hmp(-) groups, and six acetates. Clusters 1, 2, and 3 are thus at the Ce(IV)6Mn(III)2Mn(IV)2, Ce(IV)Mn(III)8, and Ce(III)2Mn(III)4 oxidation levels, respectively. Variable-temperature, solid-state direct current (DC) and alternating current (AC) magnetization studies on 1-3 in the 5.0-300 K range revealed predominantly antiferromagnetic exchange interactions within the complexes. For 1, fitting of the DC data to the theoretical expression for a dinuclear Mn(III)Mn(IV) complex derived using the Van Vleck equation and an isotropic spin Hamiltonian (ℋ = -2JŜi·Ŝj convention) gave a value for the exchange coupling parameter (J) of -60.4(7) cm(-1) and a Landé factor g = 2.00(1), indicating an S = 1/2 ground state. For 2, both DC and AC data indicate an S = 0 ground state, which is unprecedented for a member of the CeMn8 family and now

  13. Nanoconfinement Effects in Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kung, Harold H. [Northwestern Univ., Evanston, IL (United States)

    2016-09-19

    In this investigation, the unique properties that stem from the constrained environment and enforced proximity of functional groups at the active site were demonstrated for a number of systems. The first system is a nanocage structure with silicon-based, atom-thick shells and molecular-size cavities. The shell imparts the expected size exclusion for access to the interior cavity, and the confined space together with the hydrophobic shell strongly influences the stability of charged groups. One consequence is that the interior amine groups in a siloxane nanocage exhibit a shift in their protonation ability that is equivalent to about 4 pH units. In another nanocage structure designed to possess a core-shell structure in which the core periphery is decorated with carboxylic acid groups and the shell interior is populated with silanol groups, the restricted motion of the core results in limiting the stoichiometry of reaction between carboxylic acid and a Co2CO8 complex, which leads to formation and stabilization of Co(I) ions in the nanocage. The second designed catalytic structure is a supported, isolated, Lewis acid Sn-oxide unit derived from a (POSS)-Sn-(POSS) molecular complex (POSS = incompletely condensed silsesquioxane). The Sn center in the (POSS)-Sn-(POSS) complex is present in a tetrahedral coordination, as confirmed by single crystal x-ray crystallography and Sn NMR, and its Lewis acid character is demonstrated with its binding to amines. The retention of the tetrahedral coordination of Sn after heterogenization and mild oxidative treatment is confirmed by characterization using EXAFS, NMR, UV-vis, and DRIFT, and its Lewis acid character is confirmed by stoichiometric binding with pyridine. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. In addition, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the

  14. Seguimiento por espectroscopia infrarroja (FT-IR de la copolimerización de TEOS (tetraetilortosilicato y PDMS (polidimetilsiloxano en presencia de tbt (tetrabutiltitanio

    Directory of Open Access Journals (Sweden)

    Téllez, L.

    2004-10-01

    Full Text Available Hybrid materials have been prepared in this work through the reactions of Si and Ti alkoxides (TEOS and TBT, respectively and polydimethil siloxane (PDMS. These reactions have been studied by means of FT-IR spectroscopy during the whole reaction time. The hydrolysis of TEOS molecule has been followed by the 880 cm-1 band, and the self-condensation reactions through the 1180 and 1150 cm-1 bands. Polycondesation reaction between Si-OH groups and PDMS molecules has been followed by the 850 cm-1 band. On the other hand, the hydrolysis reaction of TBT and the self-condensation of Ti-OH groups have been followed by the 1130 and 770-510 cm-1 bands, respectively. Finally the condensation reaction between Si-OH and Ti-OH groups have been studied by the 936 cm-1 band. Results have shown that hydrolysis and condensation reactions are depending on TBT concentration. The formation of Si-O-Si cross-linked structures increases with the TBT concentrations in the reaction. The selfcondensation reaction of Si-OH grups or Ti-OH grous is very reapid forming Si-O-Si and Ti-O-Ti bonds, respectively. However, the Si-O-Ti bonds which are formed during the first moments of reaction are also rapidly broken due to H2O molecules or the reaction medium. The evolution of PDMS linear and cyclic molecules is also studied.

    Se han preparado materiales híbridos por medio de reacciones de hidrólisis y condensación de alcóxidos de Si y Ti (TEOS y TBT, respectivamente y de reacciones de copolimerización de éstos con polidimetilsiloxano (PDMS. Se han estudiado las citadas reacciones mediante espectroscopia FT-IR, desde el mismo comienzo hasta la obtención del material final. La hidrólisis del TEOS así como la autocondensación del os grupos Si-OH generados tanto para formar cadenas entrecruzadas como lineales se han seguido mediante las bandas situadas a 880, 1180 y 1150 cm-1, respectivamente. La policondensación de dichos grupos con PDMS se ha seguido por la banda a

  15. Low Temperature Regolith Bricks for In-Situ Structural Material

    Science.gov (United States)

    Grossman, Kevin; Sakthivel, Tamil S.; Mantovani, James; Seal, Sudipta

    2016-01-01

    Current technology for producing in-situ structural materials on future missions to Mars or the moon relies heavily on energy-intensive sintering processes to produce solid bricks from regolith. This process requires heating the material up to temperatures in excess of 1000 C and results in solid regolith pieces with compressive strengths in the range of 14000 to 28000 psi, but are heavily dependent on the porosity of the final material and are brittle. This method is currently preferred over a low temperature cementation process to prevent consumption of precious water and other non-renewable materials. A high strength structural material with low energy requirements is still needed for future colonization of other planets. To fulfill these requirements, a nano-functionalization process has been developed to produce structural bricks from regolith simulant and shows promising mechanical strength results. Functionalization of granular silicate particles into alkoxides using a simple low temperature chemical process produces a high surface area zeolite particles that are held together via inter-particle oxygen bonding. Addition of water in the resulting zeolite particles produces a sol-gel reaction called "inorganic polymerization" which gives a strong solid material after a curing process at 60 C. The aqueous solution by-product of the reaction is currently being investigated for its reusability; an essential component of any ISRU technology. For this study, two batches of regolith bricks are synthesized from JSC-1A; the first batch from fresh solvents and chemicals, the second batch made from the water solution by-product of the first batch. This is done to determine the feasibility of recycling necessary components of the synthesis process, mainly water. Characterization including BET surface area, SEM, and EDS has been done on the regolith bricks as well as the constituent particles,. The specific surface area of 17.53 sq m/g (average) of the granular regolith

  16. Investigation of the lithium ion mobility in cyclic model compounds and their ion conduction properties

    Energy Technology Data Exchange (ETDEWEB)

    Thielen, Joerg

    2011-07-27

    In view of both, energy density and energy drain, rechargeable lithium ion batteries outperform other present accumulator systems. However, despite great efforts over the last decades, the ideal electrolyte in terms of key characteristics such as capacity, cycle life, and most important reliable safety, has not yet been identified. Steps ahead in lithium ion battery technology require a fundamental understanding of lithium ion transport, salt association, and ion solvation within the electrolyte. Indeed, well defined model compounds allow for systematic studies of molecular ion transport. Thus, in the present work, based on the concept of immobilizing ion solvents, three main series with a cyclotriphosphazene (CTP), hexaphenylbenzene (HBP), and tetramethylcyclotetrasiloxane (TMS) scaffold were prepared. Lithium ion solvents, among others ethylene carbonate (EC), which has proven to fulfill together with propylene carbonate safety and market concerns in commercial lithium ion batteries, were attached to the different cores via alkyl spacers of variable length. All model compounds were fully characterized, pure and thermally stable up to at least 235 C, covering the requested broad range of glass transition temperatures from -78.1 C up to +6.2 C. While the CTP models tend to rearrange at elevated temperatures over time, which questions the general stability of alkoxide related (poly)phosphazenes, both, the HPB and CTP based models show no evidence of core stacking. In particular the CTP derivatives represent good solvents for various lithium salts, exhibiting no significant differences in the ionic conductivity {sigma}{sub dc} and thus indicating comparable salt dissociation and rather independent motion of cations and ions. In general, temperature-dependent bulk ionic conductivities investigated via impedance spectroscopy follow a William-Landel-Ferry (WLF) type behavior. Modifications of the alkyl spacer length were shown to influence ionic conductivities only in

  17. Optical response of Ce(III and Eu(II doped hybrid materials synthesised by Sol-Gel processing

    Directory of Open Access Journals (Sweden)

    Cordoncillo, E.

    2000-02-01

    Full Text Available This study deals with the preparation of two hybrid organic-inorganic matrices via sol–gel, starting from alkylalkoxisilanes Si(CH3(OCH2CH33 (MTEOS–SiH(CH3(OCH2CH32 (MDES, A system, and SiH(CH3(OCH2CH32 (MDES SiH(OCH2CH33 (TREOS, B system, together with zirconium n-propoxide. Another type-A is carried out by adding acetylacetone, A-acac system. The matrices are characterised by infrared spectroscopy, nuclear magnetic resonance (NMR-MAS, and chemical analysis. Optical characteristics of the matrices have been studied. A-acac and B matrices are doped with an Eu(III salt, and A and B matrices are doped with a Ce(IV salt. Absorption and emission studies show the presence of Eu(II and Ce(III. The transition metal alkoxide that catalysed cleavage of the Si–H bonds was used to reduce in situ at room temperature, the rare earth cations. Depending on chemical strategy, the resulting hybrid materials can be processed as transparent bulks or coatings which exhibit a good transparency in the UV–visible domain. Both the undoped and the rare earth doped matrices exhibit a strong blue emission.

    En este trabajo se aborda la preparación de dos matrices híbridas orgánico-inorgánicas por vía sol-gel, a partir de mezclas de alquilalcoxisilanos Si(CH3(OCH2CH33 (MTEOS–SiH(CH3(OCH2CH32 (MDES, sistema A, y SiH(CH3(OCH2CH32 (MDES–SiH(OCH2CH33 (TREOS, sistema B, en presencia de n-propóxido de circonio. Se efectúa una variación del sistema A por adición de acetilacetona, sistema A-acac. Las matrices se caracterizan por espectroscopia infrarroja, resonancia magnética nuclear (RMN-MAS y análisis químico. Se estudian las características ópticas de los materiales obtenidos. Las matrices A-acac y B se dopan con una sal de Eu(III y las matrices A y B con una sal de Ce(IV. Los estudios de absorción y emisión indican la presencia de Eu(II y Ce(III, es decir estos estados de oxidación se han generado in situ a temperatura ambiente en los

  18. Tendência à hidratação do pó de alumínio em concretos refratários contendo elevado teor de carbono Hydration of aluminum powder in high-carbon containing refractory castables

    Directory of Open Access Journals (Sweden)

    V. G. Domiciano

    2004-09-01

    efficiency of these coatings has not been examined yet in refractory castables. The present research aimed to evaluate the efficiency of SiO2 or TiO2 based coatings on inhibiting the aluminum-water reaction when added to high-carbon-containing refractory castables. These coatings were generated by metallic alkoxides or a reactive polymer, both using the Sol-Gel technique.

  19. Synthesis and characterization of palladium(II) and nickel(II) alcoholate-functionalized NHC complexes and of mixed nickel(II)-lithium(I) complexes.

    Science.gov (United States)

    Hameury, Sophie; de Frémont, Pierre; Breuil, Pierre-Alain R; Olivier-Bourbigou, Hélène; Braunstein, Pierre

    2014-05-19

    The synthesis of Pd(II) and Ni(II) alcohol-functionalized N-heterocyclic carbene (NHC) complexes was explored to examine the possible influence of the functional arm attached to the NHC backbone on their structure and reactivity and, in the case of a Ni(II) complex, on its catalytic properties in ethylene oligomerization. Starting from the alcohol-functionalized imidazolium salt [ImDiPP(C2OH)]Cl (2), the new functionalized NHC palladium(II) complex [PdCl(acac){ImDiPP(C2OH)-CNHC}] (3) was synthesized and fully characterized. Two byproducts, [PdCl{μ-ImDiPP(C2O)-CNHC,O}]2 (4) and trans-[PdCl2{ImDiPP(C2OH)-CNHC}2] (5), formed during the synthesis of 3, were also fully characterized. Acids promoted the transformation of 3 into the new CNHC-bound complex [PdCl(μ-Cl){ImDiPP(C2OH)-CNHC}]2 (6), unveiling the lability of the acac ligand and the resistance of the Pd-NHC bond to acids. Complex 6 reacted with a base to afford complex 4, in which alkoxide coordination to Pd(II) has occurred to generate a CNHC,O chelate. The stability of 3 was also assessed under basic conditions, and the new complex [Pd(acac){ImDiPP(C2O)-CNHC,O}] (7) was characterized. The new nickel(II) alcoholate-functionalized NHC complex [NiCl{μ-ImDiPP(C2O)-CNHC,O}]2 (8) was synthesized by the reaction of the imidazolium salt 2 with n-BuLi and [NiCl2(dme)]. The reaction of 8 with HCl regenerates the imidazolium and alcohol functions to give [ImDiPP(C2OH)]2[NiCl4] (9). The mixed-metal Ni(II)-Li(I) complexes [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]BF4 (10), [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]Cl (11), and [Ni{ImDiPP(C2O)-CNHC,μ-O}2LiBr] (12) were isolated and characterized. However, it was not possible to synthesize a Ni(II) alcohol-functionalized NHC complex in high yield. Small amounts of the square-planar complex [NiCl2{ImDiPP(C2OH)-CNHC}2] (13) could be isolated, and this complex was characterized by single-crystal X-ray diffraction. In 13, only the CNHC atom of the alcohol-functionalized NHC ligand is bound

  20. Production d'isobutène de haute pureté par décomposition du MTBE High-Purity Isobutene Production from Mtbe

    Directory of Open Access Journals (Sweden)

    Meunier P. B.

    2006-11-01

    Bronsted acid sites with the participation of basic sites. But some authors note an influence or participation of Lewis acid sites during the dimerization of isobutene on TiO2 or the dehydration of methanol. Dehydration occurring on resins or an oxide catalyst is inhibited by the presence of water. On oxides the alkoxide species with surface CH3O- is revealed to be the adsorbed species. A check must be made of both the preparation and acidity of catalytic formulations to minimize secondary reactions and to produce very pure isobutene.

  1. Electrospinning of nanofibers for filtration media

    Science.gov (United States)

    Park, Hyoungjun

    novel aqueous sol with titanium alkoxide was developed. As the result, the time taken for gelation or precipitation was elongated from 4 hours for the organic solvent-based sol to 4 months with the novel aqueous sol. In seeking the proper chemical composition to attain electrospinnability and maximize the period for storage before gelation, the reaction paths of hydrolysis and condensation for one of the components of the aqueous sol were investigated by nuclear magnetic resonance (NMR) spectroscopy. After hydrolysis and condensation reactions, Si-O-Ti bonds were validated to be formed by the reaction mechanism. TiO2-SiO2 composite fibers were successfully electrospun from the aqueous sol system by addition of a spinning agent followed by heat treatment. In contrast to TiO2 fibers in which anatase phase was observed after heat treatment at 500°C, anatase phase was formed at 1100°C in TiO2-SiO2 composite fibers. The formation of Ti-O-Ti bonds was retarded due to the formation of Si-O-Ti bonds, as evidenced by the NMR results. In regard to the microstructure of TiO2 fibers and TiO 2-SiO2 composite fibers with anatase phases, the TiO 2-SiO2 composite fibers were observed to have no voids or cleavages on the surface than TiO2 fibers which have coarse structures created upon crystallization at magnification of x330,000 by transmission electron microscopy. The coarse structure of TiO2 fibers characterized as having cleavages at exposed surface grain boundaries is anticipated to adversely affect the mechanical stability by enhancing crack formation and propagation which will lead to failure of the fiber. In contrast, amorphous SiO2 fills in the spaces that have been created by the development of anatase phase for TiO2-SiO2 composite fibers. Smoother surfaces were observed as well in contrast with TiO2 fibers due to the amorphous SiO2 in the continuous phase of the composite material. Based on the observations, TiO2-SiO2 composite fibers are expected to have better mechanical

  2. Polymerization in emulsion microdroplet reactors

    Science.gov (United States)

    Carroll, Nick J.

    emulsion. It was discovered surface pore size increases after just a few hours, with high number of hollow particles observed. After 3 days, the particles were irregular shaped with little surface porosity observed via scanning electron microscopy. This may indicate that the microemulsion in the standard synthesis is not at equilibrium and that the alkoxide monomer, tetraethylorthosilicate, may change surface activity over time as additional levels of hydrolysis are obtained. Monodisperse, microemulsion nanoporous particles were synthesized utilizing a microfluidic platform. Emulsification of silica precursor in a pure oil phase at the microfluidic orifice, with infusion of surfactant-laden oil phase into the device downstream of the orifice, allows for successful fluidic treatment of a low interfacial tension system and the formation of monodisperse particles. Temperate evaporation of the solvent from the droplets at ambient conditions preserves the excellent size distribution of the fluidic-formed precursor droplets during gelation. Successful synthesis of monodisperse silica particles with bimodal nanoporosity demonstrates engineering control at three different length scales: the nanoscale via surfactant molecular templating, tens of nanometers via spontaneous microemulsion templating and at the micron level through control of overall size distribution via a microfluidic platform.

  3. Synthesis, Characterization, and Catalytic Applications of Transition Metal Oxide/Carbonate Nanomaterials

    Science.gov (United States)

    Jin, Lei

    2011-12-01

    of rare earth Ln2O 2CO3 (Ln = La, Eu, Nd, and Sm) layered materials as novel basic materials for the biodiesel production. Reports on rare earth oxycarbonate Ln2O2CO3 (Ln = rare earths) layered materials as heterogeneous basic catalysts having novel low temperature catalytic activities are rare. In this thesis I successfully synthesized active rare earth (Ln = La, Nd, Eu, and Sm) metal oxycarbonate based layered materials to catalyze the transesterification process under mild conditions ( 95%) in a short reaction time (< 20 minutes). The results of low temperature activities and short reaction times with minimum energy consumption show them to have solid potential as alkali metal hydroxide/alkoxide alternatives for industrial applications.