WorldWideScience

Sample records for alkoxides

  1. Titanium alkoxide compound

    Science.gov (United States)

    Boyle, Timothy J.

    2007-08-14

    A titanium alkoxide composition is provided, as represented by the chemical formula (OC.sub.6H.sub.5N).sub.2Ti(OC.sub.6H.sub.5NH.sub.2).sub.2. As prepared, the compound is a crystalline substance with a hexavalent titanium atom bonded to two OC.sub.6H.sub.5NH.sub.2 groups and two OC.sub.6H.sub.5N groups with a theoretical molecular weight of 480.38, comprising 60.01% C, 5.04% H and 11.66% N.

  2. Alkoxide routes to Inorganic Materials

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, George H [ORNL

    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)

    K Chandran; R Nithya; K Sankaran; A Gopalan; V Ganesan

    2006-04-01

    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 capacities, thermal decomposition behaviour, etc of their end products are essential. In order to generate such data, high purity sodium alkoxides, viz. sodium methoxide, sodium ethoxide and sodium -propoxide, were prepared by reacting sodium metal with respective alcohol. 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 -propoxide are reported for the first time. The IR spectrum of sodium -propoxide is also reported for the first time.

  4. Electrochemical synthesis and characterization of tantalum alkoxides

    Institute of Scientific and Technical Information of China (English)

    YANG Sheng-hai; CAI Ya-nan; YANG Hai-ping; JIN Sheng-ming

    2009-01-01

    Tantalum(Ⅴ) propoxide (Ta(Opr~n)_5),isopropoxide (Ta(Opr~I)_5) and butoxide(Ta(Obu~n)_5) were synthesized by electro- chemical reactions of corresponding alcohol at sacrificial tantalum anode in the presence of tetraethylammonium chloride as a conductive additive.The pure products were isolated by reduced pressure distillation under 5 kPa.The crystal of Ta(Opr~l)_5 was obtained by recrystallization from hexane at -10 ℃.These samples were characterized by Fourier transform infrared spectra (FT-IR),Raman spectra,nuclear magnetic resonance spectra (NMR),TG/DTA and ICP-MS.The results show that direct electrochemical synthesis of metal alkoxides has a high current efficiency and electrolysis yield.These alkoxides have a high purity of 99.97% and can be directly used as the precursor of Ta_2O_5 films.

  5. Direct synthesis of some significant metal alkoxides

    International Nuclear Information System (INIS)

    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)

  6. 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.

  7. Thermal decomposition kinetics of sodium alkoxides - model independent method

    International Nuclear Information System (INIS)

    Sodium alkoxides namely sodium methoxide and sodium ethoxide were synthesized and characterized by various analytical techniques. Thermal decomposition of these compounds was studied under constant heating rate using thermogravimetric analyzer coupled with mass spectrometer (TGA-MS). On decomposition, these sodium alkoxides form gaseous products of saturated and unsaturated hydrocarbons and leave sodium carbonate, sodium hydroxide and free carbon as residue. Kinetic parameters namely activation energy and pre-exponential factor were deduced from the dynamic TGA data by physical model independent (iso-conversion) method. (author)

  8. Mechanisms and kinetics of the hydrolysis and condensation of alkoxides

    OpenAIRE

    Schmidt, Helmut K.; Scholze, Horst

    1985-01-01

    Hydrolysis and condensation of alkoxides involve different reaction steps. Generally the first step is the dissolution of monomers in organic solvents like alcohols. The second step is hydrolysis, where in most cases condensation may not be separated. Dissolution may incorporate solvatation, coordination, complexation of polymerization. The addition of water leads to hydrolysis of Si-O-C bonds and subsequently condensation of silanoles takes place. Another possibility of reaction is the hydro...

  9. A planar oxocuprate(II) array via heterometallic alkoxide chemistry

    International Nuclear Information System (INIS)

    Application of the molecular precursor method to the synthesis of copper-based high-temperature superconductors rests on the authors ability to produce copper containing heterometallic alkoxides. They have reported recently on the chemistry of the anion Zr2-(OiPr)9-, which is related to recent reports by the group of Mehrotra. They report here their investigation of the coupling of this and related anions to CuCl2 of relevance to hydrolytic routes to copper/oxo superconductors

  10. Heterolysis of Dihydrogen by Silver Alkoxides and Fluorides.

    Science.gov (United States)

    Tate, Brandon K; Nguyen, Jenna T; Bacsa, John; Sadighi, Joseph P

    2015-07-01

    Alkoxide-bridged disilver cations react with dihydrogen to form hydride-bridged cations, releasing free alcohol. Hydrogenolysis of neutral silver fluorides affords hydride-bridged disilver cations as their bifluoride salts. These reactions proceed most efficiently when the supporting ligands are expanded N-heterocyclic carbenes (NHCs) derived from 6- and 7-membered cyclic amidinium salts. Kinetics studies show that silver fluoride hydrogenolysis is first-order in both silver and dihydrogen.

  11. Metal alkoxides as starting materials for hydrolysis processes

    International Nuclear Information System (INIS)

    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)

  12. A planar oxocuprate(II) array via heterometallic alkoxide chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Samuels, J.A.; Vaarttra, B.A.; Huffman, J.C.; Trojan, K.L.; Hatfield, W.E.; Caulton, K.G. (Indiana Univ., Bloomington (United States) Univ. of North Carolina, Chapel Hill (United States))

    1990-12-19

    Application of the molecular precursor method to the synthesis of copper-based high-temperature superconductors rests on the authors ability to produce copper containing heterometallic alkoxides. They have reported recently on the chemistry of the anion Zr{sub 2}-(O{sup i}Pr){sub 9}{sup {minus}}, which is related to recent reports by the group of Mehrotra. They report here their investigation of the coupling of this and related anions to CuCl{sub 2} of relevance to hydrolytic routes to copper/oxo superconductors.

  13. Perspectives of applications of alkoxide sol-gel process in heterogeneous catalysis

    International Nuclear Information System (INIS)

    Basic principles, specific features, advantages and drawbacks of alkoxide technology application for the preparation of oxide heterogeneous catalysts and carriers (RuO, V2O5, ZrO2, B2O3) have been considered. Application of acetylacetonates E(acac)n is considered alongside with mixed alkoxyacetylacetonates E(OR)x(acac)n-1. The lack of extensive commercial production of Al and Zr alkoxides in Russia rather than their high cost, is a real obstacle for alkoxide technology introduction. 293 refs., 2 figs., 2 tabs

  14. Negative Hyperconjugation versus Electronegativity: Vibrational Spectra of Free Fluorinated Alkoxide Ions in the Gas Phase

    NARCIS (Netherlands)

    J. Oomens; G. Berden; T.H. Morton

    2015-01-01

    CO stretching frequencies of free, gaseous, fluorinated alkoxide ions shift substantially to the blue, relative to those of corresponding alcohols complexed with ammonia. Free -fluorinated ions, pentafluoroethoxide and heptafluoroisopropoxide anions, display further blue shifts relative to cases wit

  15. Optical and electrical properties of vanadium oxide films deposited from alkoxides

    OpenAIRE

    Livaje, J.

    1998-01-01

    Vanadium oxide thi n films are formed via the hydrolysis and condensation of vanadium alkoxides. Sol-gel chemistry provides a chemical control over condensation reactions and different materials are actually obtained depending on experimental conditions. The hydrolysis of vanadium alkoxide in the presence of an excess of water leads to ribbon-like particles of hydrated oxide V205.nH20. Coatings with a preferred orientation are then deposited from these gels. They exhibit improved ele...

  16. Photoinduced Formation of Colloidal Silver in Nitrocellulose Solutions Containing Titanium Alkoxides

    Science.gov (United States)

    Kulak, A. I.; Branitsky, G. A.

    2016-07-01

    The study shows the possibility of photo-induced reduction of silver nitrate and formation of stable colloidal silver particles in an isopropanol-N,N-dimethylacetamide solution of titanium alkoxide (polybutyl titanate) stabilized by nitrocellulose. It is established that titanium alkoxide and the products of its partial hydrolysis in the liquid composition play the role of a photocatalyst for the reduction of silver ions; the introduction of nitric or acetic acid additives to the composition significantly increases its photosensitivity. The films deposited from the liquid composition, previously irradiated with visible or UV light, consist of hydrated titanium dioxide and nitrocellulose with incorporated colloidal silver. Thermal treatment of the films at 150-245°C leads to the decomposition of nitrocellulose and an increase in the absorption by silver particles.

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

    OpenAIRE

    Spijksma, Gerald Iwan

    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 process and their effect on the derived materials has been addressed. A specific focus has been on the preparation of microporous materials by sol-gel for the application in membranes.

  18. Hydrolytic activity of -alkoxide/acetato-bridged binuclear Cu(II) complexes towards carboxylic acid ester

    Indian Academy of Sciences (India)

    Weidong Jiang; Bin Xu; Zhen Xiang; Shengtian Huang; Fuan Liu; Ying Wang

    2013-09-01

    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 background value for PNPP hydrolysis at neutral conditions, respectively. For comparing, activities of the other two mononuclear analogues were evaluated, revealing that binuclear complexes show approximately 150- and 171-fold kinetic advantage over their mononuclear analogues.

  19. Negative Hyperconjugation versus Electronegativity: Vibrational Spectra of Free Fluorinated Alkoxide Ions in the Gas Phase.

    Science.gov (United States)

    Oomens, Jos; Berden, Giel; Morton, Thomas Hellman

    2015-06-22

    CO stretching frequencies of free, gaseous, fluorinated alkoxide ions shift substantially to the blue, relative to those of corresponding alcohols complexed with ammonia. Free α-fluorinated ions, pentafluoroethoxide and heptafluoroisopropoxide anions, display further blue shifts relative to cases with only β-fluorination, providing experimental evidence for fluorine negative hyperconjugation. DFT analysis with the atoms in molecules (AIM) method confirms an increase in CO bond order for the α-fluorinated ions, demonstrating an increase in carbonyl character for the free ions.

  20. 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.

  1. Fast microwave treatments of single source alkoxides for nanostructured Li-ion battery electrodes.

    Science.gov (United States)

    Laveda, Josefa Vidal; Chandhok, Vibhuti; Murray, Claire A; Paterson, Gary W; Corr, Serena A

    2016-07-12

    Microwave or ultrasonic treatment of metal alkoxides presents a fast, low cost route to both anode and cathode nanomaterials for Li-ion battery applications. Here, we demonstrate the formation of LiMPO4 (M = Fe, Mn) and Mn3O4 nanostructures via this simple route which exhibit excellent electrochemical performances. This approach opens up a new avenue for the targeted design of nanostructured materials, where co-location of the desired metals in a single starting material shortens reaction times and temperatures since there is a decrease in diffusional energy requirements usually needed for these reactions to proceed. PMID:26486274

  2. 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.

  3. Synthesis, structure determination, and sol-gel processing of heterometallic heteroleptic alkoxide complexes of late transition metals

    OpenAIRE

    Werndrup, Pia

    2005-01-01

    The thesis describes synthesis of single-source precursors (SSP) for sol-gel preparation of thin films and nanocomposites. The structures of the SSPs were determined by single-crystal X-ray studies and a new group of heterometallic heteroleptic alkoxide complexes have been described, the MII2MV2(acac)2(OR)12 complex, MII= Co, Ni, Zn or Mg, and MV= Ta or Nb, R= Et or Me. Changing to molybdenum oxomethoxide, MoO(OMe)4, instead of tantalum or niobium alkoxide, in the reaction with cobalt acetyla...

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

    International Nuclear Information System (INIS)

    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 oC by the chlorides route, whereas alkoxide precursors needed firing over 900 oC and nitrates even over 1100 oC. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 oC with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  5. Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study

    Indian Academy of Sciences (India)

    Akshai Kumar; Ashoka G Samuelson

    2011-01-01

    The insertion reactions of zirconium(IV) -butoxide and titanium(IV) -butoxide with a heterocumulene like carbodiimide, carbon dioxide or phenyl isocyanate are compared. Both give an intermediate which carries out metathesis at elevated temperatures by inserting a second heterocumulene in a head-to-head fashion. The intermediate metallacycle extrudes a new heterocumulene, different from the two that have inserted leading to metathesis. As the reaction is reversible, catalytic metathesis is feasible. In stoichiometric reactions heterocumulene insertion, metathesis and metathesis cum insertion products are observed. However, catalytic amounts of the metal alkoxide primarily led to metathesis products. It is shown that zirconium alkoxides promote catalytic metathesis (isocyanates, carbon dioxide) more efficiently than the corresponding titanium alkoxide. The difference in the metathetic activity of these alkoxides has been explained by a computational study using model complexes Ti(OMe)4 (1bTi) and Zr(OMe)4 (1bZr). The computation was carried out at the B3LYP/LANL2DZ level of theory.

  6. Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Vettori, Irene; Ruiz-Agudo, Encarnacion

    2016-05-24

    Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol(-1) for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preserving the external hexagonal (platelike) morphology of the parent phase. Textural and kinetic results reveal that this pseudomorphic replacement involves a 3D diffusion-controlled deceleratory advancement of the reaction front. The results are consistent with an interface-coupled dissolution-precipitation replacement mechanism. Analysis of the carbonation of Ca(OH)2 particles with different degree of conversion into Ca-ethoxide (α up to 0.08) and Ca-isopropoxide (α up to 0.04) exposed to air (20 °C, 80% relative humidity) reveals that Ca-alkoxides significantly reduce the rate of transformation into cementing CaCO3 and induce the formation of metastable vaterite, as opposed to stable calcite which forms in untransformed Ca(OH)2 samples. Similar effects are obtained when a commercial nanolime partially transformed into Ca-ethoxide is subjected to carbonation. Such effects may hamper/delay the strengthening or consolidation effects of nanolimes, thus having

  7. Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Vettori, Irene; Ruiz-Agudo, Encarnacion

    2016-05-24

    Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol(-1) for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preserving the external hexagonal (platelike) morphology of the parent phase. Textural and kinetic results reveal that this pseudomorphic replacement involves a 3D diffusion-controlled deceleratory advancement of the reaction front. The results are consistent with an interface-coupled dissolution-precipitation replacement mechanism. Analysis of the carbonation of Ca(OH)2 particles with different degree of conversion into Ca-ethoxide (α up to 0.08) and Ca-isopropoxide (α up to 0.04) exposed to air (20 °C, 80% relative humidity) reveals that Ca-alkoxides significantly reduce the rate of transformation into cementing CaCO3 and induce the formation of metastable vaterite, as opposed to stable calcite which forms in untransformed Ca(OH)2 samples. Similar effects are obtained when a commercial nanolime partially transformed into Ca-ethoxide is subjected to carbonation. Such effects may hamper/delay the strengthening or consolidation effects of nanolimes, thus having

  8. Synthesis of Industrially Relevant Carbamates towards Isocyanates using Carbon Dioxide and Organotin(IV) Alkoxides.

    Science.gov (United States)

    Germain, Nicolas; Müller, Imke; Hanauer, Matthias; Paciello, Rocco A; Baumann, Robert; Trapp, Oliver; Schaub, Thomas

    2016-07-01

    A straightforward phosgene-free synthesis of aromatic isocyanates and diisocyanates is disclosed. Theoretical investigations suggested that the insertion of carbon dioxide (CO2 ) by dialkyltin(IV) dialkoxides could be used to convert aromatic amines into aromatic mono- and dicarbamates. Here we show, that methyl phenylcarbamate (MPC) from aniline using organotin(IV) dimethoxide and CO2 can be formed in high yield of up to 92 %, experimentally corroborating the predictions of density functional theory (DFT) calculations. MPC was then separated from the tin oxide residues and converted into phenyl isocyanate. Furthermore, organotin(IV) alkoxides could be regenerated from the tin oxide residues and reused, paving the way for a continuous industrial process. Extension of the scope to the synthesis of diurethanes from toluene 2,4-diamine and 4,4'-methylenedianiline could potentially allow the efficient production of industrially relevant diisocyanates. PMID:27319978

  9. Fast and reversible insertion of carbon dioxide into zirconocene-alkoxide bonds. A mechanistic study.

    Science.gov (United States)

    Brink, Alice; Truedsson, Ida; Fleckhaus, André; Johnson, Magnus T; Norrby, Per Ola; Roodt, Andreas; Wendt, Ola F

    2014-06-21

    In two consecutive equilibria the compound (Cp*)2Zr(OMe)2 undergoes insertion of CO2 to form the mono- and bis-hemicarbonates. Both equilibria are exothermic but entropically disfavoured. Magnetisation transfer experiments gave kinetic data for the first equilibrium showing that the rate of insertion is overall second order with a rate constant of 3.20 ± 0.12 M(-1) s(-1), which is substantially higher than those reported for other early transition metal alkoxides, which are currently the best homogeneous catalysts for dimethyl carbonate formation from methanol and CO2. Activation parameters for the insertion reaction point to a highly ordered transition state and we interpret that as there being a substantial interaction between the CO2 and the metal during the C-O bond formation. This is supported by DFT calculations showing the lateral attack by CO2 to have the lowest energy transition state. PMID:24796283

  10. LiOOt-Bu as a terminal oxidant in a titanium alkoxide-mediated [2+2+2] reaction cascade☆

    Science.gov (United States)

    Kim, Wan Shin; Aquino, Claudio; Mizoguchi, Haruki; Micalizio, Glenn C.

    2015-01-01

    LiOOt-Bu is an effective oxidant for converting the penultimate organometallic intermediate generated in a titanium alkoxide-mediated [2+2+2] reaction cascade to an allylic alcohol. Oxidation of the presumed allylic titanium species is highly regioselective, providing direct access to substituted hydroindanes containing a primary allylic alcohol. In addition to demonstrating the feasibility of this oxidation process, we document the ability to convert the primary allylic alcohol products to angularly substituted cis-fused hydroindanes. PMID:26097265

  11. Synthesis and Characterization of Fluoro- and Chlorobimetallic Alkoxides as Precursors for Luminescent Metal Oxide Materials via Sol-Gel Technique

    Institute of Scientific and Technical Information of China (English)

    ATHAR, Taimur; SEOK, Sang II; KWON, Jeong Oh

    2007-01-01

    Heterobimetallic alkoxides are broadly recognized as versatile precursors for luminescence materials, and efforts are being made to develop novel routes by applying the concept of geometrical molecular design, for their synthesis and to design a single source precursor suited to photoluminescent materials. Novel and new series of bimetallic alkoxides has been prepared by metathesis route. They exhibit a lower sensitivity towards hydrolysis and so they are easier to handle as compared to other alkoxides. All the compounds were characterized by elemental analysis, FT-IR and multinuclear NMR spectroscopies. FT-IR revealed that the molecular structure of these metal spectroscopy provided useful information about chemical shifts for better understanding the likely structure based on interactions with their coordinate metals. The mass spectra show similar types of fragmentation pattern.SEM-EDS analyses showed consistency with the formulation. XRD patterns show an enhanced homogeneity at high temperature. TGA measurements show that thermal decomposition occured in steps that depended entirely on the chemical compositions and the synthesis routes. SEM observation reveals that the morphology and particle size strongly depend on synthesis routes for their precursors.

  12. Thermomechanical properties of aluminum alkoxide (alucone) films created using molecular layer deposition

    International Nuclear Information System (INIS)

    Nanometer-scale-thick, polymer-like coatings deposited using the molecular layer deposition (MLD) technique constitute a new class of materials. The modulus and hardness of aluminum alkoxide ('alucone') films grown using either homobifunctional or heterobifunctional reactants were measured using nanoindentation. Because the coatings are brittle and possess a significant tensile film stress immediately after deposition, the influence of film stress on the indentation measurements was quantified using a numerical analysis protocol. The film stress and coefficient of thermal expansion for alucone were determined using the wafer curvature method. Film stress was found to stabilize within the first thermal cycle, demonstrating a repeatable hysteresis thereafter. Curvature/time measurements on coated microcantilever beams indicated that the most significant evolution in film stress for alucone occurred during the initial 2 weeks of storage in the ambient environment. The temporal behavior is attributed to the change in thickness and/or modulus of alucone, and is consistent with the film stress becoming more compressive over time. An encapsulating alumina film, coated using the atomic layer deposition technique, was found to suppress the evolution of stress within alucone. The studies here suggest that the alucones have a greater elastic modulus than traditional polymers, are at present quite brittle and are prone to environmental influence. The MLD technique, however, possesses a rich wealth of options that enable the modulus, adhesion and chemical stability of the coatings to be tailored.

  13. Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

    Directory of Open Access Journals (Sweden)

    Tanel Tätte, Medhat Hussainov, Madis Paalo, Marko Part, Rasmus Talviste, Valter Kiisk, Hugo Mändar, Kaija Põhako, Tõnis Pehk, Kaido Reivelt, Marco Natali, Jonas Gurauskis, Ants Lõhmus and Uno Mäeorg

    2011-01-01

    Full Text Available The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2 fibres with a high aspect ratio (up to 10 000 and a diameter as small as 200 nm. The sol–gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

  14. Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

    Energy Technology Data Exchange (ETDEWEB)

    Taette, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Maendar, Hugo; Pohako, Kaija; Reivelt, Kaido; Lohmus, Ants [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Pehk, Tonis [National Institute of Chemical and Biological Physics, Akadeemia tee 23, Tallinn 12618 (Estonia); Natali, Marco [ICIS-CNR, Corso Stati Uniti 4, Padova 35127 (Italy); Gurauskis, Jonas [Instituto de Ciencia de Materiales de Aragon C.S.I.C., University of Zaragoza Fac. De Ciencias, c/Pedro Cerbuna 12, Zaragoza 50009 (Spain); Maeeorg, Uno, E-mail: tanelt@fi.tartu.ee [Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411 (Estonia)

    2011-06-15

    The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO{sub 2}, TiO{sub 2}, ZrO{sub 2}, HfO{sub 2} and CeO{sub 2}) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

  15. Alcohol adducts of alkoxides: Intramolecular hydrogen bonding as a general structural feature

    International Nuclear Information System (INIS)

    Characterization of Zr2(OiPr)8(iPrOH)2 by 1H and 13C NMR spectroscopy, ir spectroscopy, and single-crystal x-ray diffraction (-100 degree C) is reported. The unit cell contains four half-dimers in the asymmetric unit, all of which differ only in the rotational conformation about Zr-O and O-C bonds. In each dimer, the edge-shared bioctahedron has two μ-OiPr groups. On opposite sides of this Zr2(μ-OR)2 plane, each dimer forms two hydrogen bonds, one each between a coordinated alcohol and a terminal alkoxide. The NMR spectra at 25 degree C are so simple as to be structurally uninformative, a result of rapid fluxionality which includes, as one component, proton migration among all OiPr units. At -80 degree C in toluene, the NMR spectra are now too complex to be accounted for by a single edge-shared bioctahedral structure. The hafnium analogue is isomorphous with the zirconium compound. Although Ce2(OiPr)8(iPrOH)2 is not isomorphous, it exhibits an analogous hydrogen-bonded structure in which the O hor-ellipsis O distance is as short as it is in the Zr analogue, in spite of a metal-metal separation which is longer by 0.28 angstrom. The generality of hydrogen bonding between M-OR and M-O(H)R groups when they are aligned parallel in a metal cluster is reviewed. 44 refs., 2 figs., 4 tabs

  16. Preparation of zirconia coatings by hydrolysis of zirconium alkoxide with hydrogen peroxide

    International Nuclear Information System (INIS)

    Zirconia has gained a great deal of attention because of its superior properties of mechanical strength, chemical resistance, and ionic conductivity. Zirconia coatings and thin films are receiving attention as tribological and thermal barrier coatings for engines, high-reflective coatings, solid electrolytes for fuel cells, oxygen sensors, etc. The sol-gel coating method has several advantages, such as low processing temperatures, homogeneity, control of micro-structure, and good productivity compared to chemical vapor deposition and physical vapor deposition. However, there are few reports concerning the preparation of zirconia coatings and thin films by the sol-gel method. Up to the present, zirconia coatings have been prepared from zirconium propoxide (not heated), zirconium tetrabutoxide modified by acetylacetone and ethyl acetoacetate, zirconium diethoxydichloride (ZrCl2(OC2H5)2), and a hydrosol prepared from a zirconium oxychloride solution. Coatings of 8.8-mol%-yttria-doped zirconia were fabricated using a transparent and spinnable sol prepared by hydrolysis of zirconium alkoxide with hydrogen peroxide and nitric acid. The sol gave a crack-free coating film consisting of fine grains. The crystalline phase was cubic after heating of 1,000 and 1,200 C and cubic and tetragonal at 1,350 C, with the coating being highly oriented in the (111) plane, especially at 1,000 C. Activation energy of the coating films was higher than that of the bulk. Transmittance through a film thickness of about 0.3 μm on each side was 75%

  17. Synthesis, Radical Reactivity, and Thermochemistry of Monomeric Cu(II) Alkoxide Complexes Relevant to Cu/Radical Alcohol Oxidation Catalysis.

    Science.gov (United States)

    Porter, Thomas R; Capitao, Dany; Kaminsky, Werner; Qian, Zhaoshen; Mayer, James M

    2016-06-01

    Two new monomeric Cu(II) alkoxide complexes were prepared and fully characterized as models for intermediates in copper/radical mediated alcohol oxidation catalysis: Tp(tBuR)Cu(II)OCH2CF3 with Tp(tBu) = hydro-tris(3-tert-butyl-pyrazol-1-yl)borate 1 or Tp(tBuMe) = hydro-tris(3-tert-butyl-5-methyl-pyrazol-1-yl)borate 2. These complexes were made as models for potential intermediates in enzymatic and synthetic catalytic cycles for alcohol oxidation. However, the alkoxide ligands are not readily oxidized by loss of H; instead, these complexes were found to be hydrogen atom acceptors. They oxidize the hydroxylamine TEMPOH, 2,4,6-tri-t-butylphenol, and 1,4-cyclohexadiene to the nitroxyl radical, phenoxyl radical, and benzene, with formation of HOCH2CF3 (TFE) and the Cu(I) complexes Tp(tBuR)Cu(I)-MeCN in dichloromethane/1% MeCN or 1/2 [Tp(tBuR)Cu(I)]2 in toluene. On the basis of thermodynamics and kinetics arguments, these reactions likely proceed through concerted proton-electron transfer mechanisms. Thermochemical analyses give lower limits for the "effective bond dissociation free energies (BDFE)" of the O-H bonds in 1/2[Tp(tBuR)Cu(I)]2 + TFE and upper limits for the free energies associated with alkoxide oxidations via hydrogen atom transfer (effective alkoxide α-C-H BDFEs). These values are summations of the free energies of multiple chemical steps, which include the energetically favorable formation of 1/2[Tp(tBuR)Cu(I)]2. The effective alkoxide α-C-H bonds are very weak, BDFE ≤ 38 ± 4 kcal mol(-1) for 1 and ≤44 ± 5 kcal mol(-1) for 2 (gas-phase estimates), because C-H homolysis is thermodynamically coupled to one electron transfer to Cu(II) as well as the favorable formation of the 1/2[Tp(tBuR)Cu(I)]2 dimer. Treating 1 with the H atom acceptor (t)Bu3ArO(•) did not result in the expected alkoxide oxidation to an aldehyde, but rather net 2,2,2-trifluoroethoxyl radical transfer occurred to generate an unusual 2-substituted dienone-ether product. Treating 2

  18. The nature of the alkoxide group, solvent, catalyst, and concentration on the gelation and porosity of hexylene-bridged polysilsesquioxanes

    Energy Technology Data Exchange (ETDEWEB)

    Loy, D. A. (Douglas A.); Small, J. H. (James H.)

    2004-01-01

    Hexylene-bridged polysilsesquioxanes are hybrid organic-inorganic materials prepared by the sol-gel polymerization of 1,6-bis(trialkoxysilyl)hexane monomers: (1) R = Methyl; (2) R = Ethyl; and (3) R = n-Propyl. Previous studies showed that high surface area xerogels could be prepared from 2 with base catalyzed polymerizations while non-porous xerogels could be prepared with acidic catalysts. The object of this study was to ascertain the influences of monomer alkoxide group, solvent, catalyst, and monomer concentration on gelation time, and the properties of the resulting xerogels.This study has provided some insight into the chemical parameters that affect the ultimate structure in bridged polysilsesquioxanes. First, gelation times do not necessarily directly reflect the hydrolysis and condensation rates expected for different alkoxide groups. The collapse of porosity during the drying of hexylene-bridged polysilsesquioxanes occurs in nearly all acid-catalyzed samples, save those that form quickly due to concentration or from the methoxide monomer 1 in methanolic solution. This suggests that there may be a kinetic contribution to creating porosity in addition to the network compliance model. It would also appear that syneresis of gels during aging may be the symptom of changes resulting in increased porosity. Whatever these changes may be due to, they do not appear to significantly alter the structural composition. Experiments are underway to provide more information and test some of these hypotheses.

  19. 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.

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

    NARCIS (Netherlands)

    Chubar, N.

    2011-01-01

    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

  1. Syntheses, Structures and Thermal Studies of Fluorinated and Non-Fluorinated Homo and Heterometallic Alkoxides

    Science.gov (United States)

    Samuels, John Andrew

    The following studies probe the effects of ligand structure and modification on the conversion of metal species to solid-state products. 1. The synthesis, characterization, thermal decomposition, and full hydrolysis of rm Cu^{I }_2 Zr_2(O^{i}Pr) _{10} (1), Cu^ {rm I}_4Zr_4 O(O^{rm i}Pr) _{18} (2), and Cu ^{rm II}_4Zr _4O_3(O^ {rm i}Pr)_{18 } (3) are reported. The structure of 1 contains a Zr_2(O^{rm i}Pr)_9^- face -sharing bioctahedron bound to a Cu^{ rm I}_2(mu_2-OR) ^+ fragment via two mu _2 -alkoxides. The structure for 2 contains two (C_2(mu_2-OR) _2Zr_2(mu_2 -OR)_3(OR)_4] ^{1-} fragments connected via a pseudo-tetrahedral mu_4-O ^{2-} ligand. The structure of 3 contains a planar Cu_4O(O ^{rm i}Pr)_2 ^{4+} fragment capped by two Zr _2O(O^{rm i}Pr)_8^{2-} face-sharing bioctahedral units. The central oxo of the copper fragment is square-planar. TGA studies of ClCuZr_2(O^{ rm i}Pr)_9, 1, 2, and 3 show that internal redox occurs, producing copper metal, acetone, and isopropanol. The final products contain an increasing amount of zirconia with increasing number of oxo ligands in the precursor species. Full hydrolysis of 1 and 3, followed by thermolysis, produces Cu ^0, Cu_2O, and CuO with zirconia, depending on thermolysis conditions. 2. The compounds Na(HFIP) (HFIP = OCH(CF _3)_2), 1a, Na(TFTB) (TFTB = OC(CH _3)_2(CF_3 )), 1b, Na(HFTB) (HFTB = OC(CH_3 )(CF_3)_2), 1c, Na(PFTB) (PFTB = OC(CF_3)_3), 1d, Zr(HFIP)_4, 2a, Zr(TFTB) _4, 2b, Zr(HFTB)_4, 2c, Zr(PFTB)_4, 2d, Na_2 Zr(OR_{rm f})_6 (C_6H_6)_ {rm n} (3a when n = 1 and 3b when n = 2), and Tl_2Zr(OR_ {rm f})_6, 4, have been synthesized and characterized by mass spectrometry, multinuclear NMR and (for 1a, 2c, 3a, 3b and 4) X-ray diffraction structure determinations. Intramolecular bonding interactions between organofluorines and sodium or thallium are seen in all structures and are supported by Tl/F coupling in ^{205}Tl and ^{19 }F NMR spectra. Chemical vapor depositions of 1a-d, 2b-d and 3 produce metal fluoride

  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. Fabrication and performances of MWCNT/TiO2 composites derived from MWCNTs and titanium (IV) alkoxide precursors

    Indian Academy of Sciences (India)

    Mingliang Chen; Fengjun Zhang; Wonchun Oh

    2011-07-01

    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 surface area, SEM, XRD, EDX and UV-Vis absorption spectroscopy. The samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under UV irradiation. The results indicated that the sample MPB had best excellent photocatalytic activity among the three kinds of samples. Furthermore, we also used piggery waste to determine the photocatalytic activity for the MWCNT/TiO2 composites by using a chemical oxygen demand (COD) method. It seemed all of the samples have an excellent removal effect of COD. From the results of the bactericidal test, MWCNT/TiO2 composites with sunlight had a greater effect on E. coli than any other experimental conditions.

  4. Preparation of epoxy/zirconia hybrid materials via in situ polymerization using zirconium alkoxide coordinated with acid anhydride

    International Nuclear Information System (INIS)

    Highlights: → Novel epoxy/zirconia hybrid materials were synthesized via in situ polymerization using zirconium alkoxide coordinated with acid anhydride. → The half-ester compound of acid anhydride desorbed from zirconium played as curing agent of epoxy resin. → The zirconia was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale by synchronizing the epoxy curing and sol-gel reactions. → The refractive indices of the hybrid materials significantly improved with an increase in the zirconia content. - Abstract: Novel epoxy/zirconia hybrid materials were synthesized using a bisphenol A epoxy resin (diglycidyl ether of bisphenol A; DGEBA), zirconium(IV)-n-propoxide (ZTNP), and hexahydrophthalic anhydride (HHPA) via in situ polymerization. HHPA played two roles in this system: it acted as a modifier to control the hydrolysis and condensation reactions of zirconium alkoxide and also as a curing agent - the half-ester compound of HHPA desorbed from zirconium reacted with the epoxy resin to form the epoxy network. As a result, both the sol-gel reaction and epoxy curing occurred simultaneously in a homogeneous solution, and organic-inorganic hybrid materials were readily obtained. Further, the zirconia produced by the in situ polymerization was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale; thus, hybrid materials that exhibited excellent optical transparency were obtained. Furthermore, the heat resistance of the hybrid materials could be improved by hybridization with zirconia. And, the refractive indices of the hybrid materials significantly improved with an increase in the zirconia content.

  5. Preparation of epoxy/zirconia hybrid materials via in situ polymerization using zirconium alkoxide coordinated with acid anhydride

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Mitsukazu, E-mail: mochi@ipcku.kansai-u.ac.jp [Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Suita-shi, Osaka 564-8680 (Japan); Nii, Daisuke; Harada, Miyuki [Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Suita-shi, Osaka 564-8680 (Japan)

    2011-09-15

    Highlights: {yields} Novel epoxy/zirconia hybrid materials were synthesized via in situ polymerization using zirconium alkoxide coordinated with acid anhydride. {yields} The half-ester compound of acid anhydride desorbed from zirconium played as curing agent of epoxy resin. {yields} The zirconia was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale by synchronizing the epoxy curing and sol-gel reactions. {yields} The refractive indices of the hybrid materials significantly improved with an increase in the zirconia content. - Abstract: Novel epoxy/zirconia hybrid materials were synthesized using a bisphenol A epoxy resin (diglycidyl ether of bisphenol A; DGEBA), zirconium(IV)-n-propoxide (ZTNP), and hexahydrophthalic anhydride (HHPA) via in situ polymerization. HHPA played two roles in this system: it acted as a modifier to control the hydrolysis and condensation reactions of zirconium alkoxide and also as a curing agent - the half-ester compound of HHPA desorbed from zirconium reacted with the epoxy resin to form the epoxy network. As a result, both the sol-gel reaction and epoxy curing occurred simultaneously in a homogeneous solution, and organic-inorganic hybrid materials were readily obtained. Further, the zirconia produced by the in situ polymerization was uniformly dispersed in the epoxy matrix on the nanometer or sub-nanometer scale; thus, hybrid materials that exhibited excellent optical transparency were obtained. Furthermore, the heat resistance of the hybrid materials could be improved by hybridization with zirconia. And, the refractive indices of the hybrid materials significantly improved with an increase in the zirconia content.

  6. 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.

  7. Reactions of ketones with uranium tetraborohydride, mechanism and stereoselectivity, synthesis and structure of uranium (IV) tetrahydroborato alkoxide complexes

    International Nuclear Information System (INIS)

    The mono- and bisalkoxide uranium complexes U(BH4)3(OCHR1R2)(THF)2 1 and U(BH4)2(OCHR1R2)2(THF)2 2 were prepared successively in tetrahydrofuran (THF) by treatment of U(BH4)4 with the corresponding ketone R1R2C = O (acetone, benzophenone, cyclohexanone, 2-methylcyclohexanone, 4-tert-butylcyclohexanone, and norcamphor). The borane BH3.THF was liberated during the formation of 1 and 2, and reacted with the ketone to give the alkoxyborane species B(OCHR1R2)nH3-n. Formation of 1 also resulted from: a) reaction of U-BH4)4 with the alkoxyborane species; b) reaction of U(BH4)4 with 2; and c) reaction of 2 with BH3.THF. The alkoxide groups of 1 and 2 rapidly exchange with those of the alkoxyborane species. The uranium complexes 1 and alkoxyborane species resulting from the reaction of U(BH4)4 with the substituted cyclohexanones or norcamphor have been separated and their hydrolysis afforded the corresponding epimeric alcohols in different proportions. The monoalkoxide compounds 1 were alternatively prepared by reaction of the ketones R1R2C = O with UCl4 in the presence of LiBH4 or by treatment of U(BH4)4 with the alcohols R1R2CHOH. The octahedral crystal structures of U(BH4)3(OCHPh2)(THF)2 1b and U(BH4)2(OCHPh2)2(THF)2 2b show that in 1b, the two equatorial THF ligands (and the two equatorial BH4 groups) are in relative cis positions whereas they are trans in 2b

  8. Electronic Structure of a Cu(II)-Alkoxide Complex Modeling Intermediates in Copper-Catalyzed Alcohol Oxidations.

    Science.gov (United States)

    Hayes, Ellen C; Porter, Thomas R; Barrows, Charles J; Kaminsky, Werner; Mayer, James M; Stoll, Stefan

    2016-03-30

    In the copper-catalyzed oxidation of alcohols to aldehydes, a Cu(II)-alkoxide (Cu(II)-OR) intermediate is believed to modulate the αC-H bond strength of the deprotonated substrate to facilitate the oxidation. As a structural model for these intermediates, we characterized the electronic structure of the stable compound Tp(tBu)Cu(II)(OCH2CF3) (Tp(tBu) = hydro-tris(3-tert-butyl-pyrazolyl)borate) and investigated the influence of the trifluoroethoxide ligand on the electronic structure of the complex. The compound exhibits an electron paramagnetic resonance (EPR) spectrum with an unusually large gzz value of 2.44 and a small copper hyperfine coupling Azz of 40 × 10(-4) cm(-1) (120 MHz). Single-crystal electron nuclear double resonance (ENDOR) spectra show that the unpaired spin population is highly localized on the copper ion (≈68%), with no more than 15% on the ethoxide oxygen. Electronic absorption and magnetic circular dichroism (MCD) spectra show weak ligand-field transitions between 5000 and 12,000 cm(-1) and an intense ethoxide-to-copper charge transfer (LMCT) transition at 24,000 cm(-1), resulting in the red color of this complex. Resonance Raman (rR) spectroscopy reveals a Cu-O stretch mode at 592 cm(-1). Quantum chemical calculations support the interpretation and assignment of the experimental data. Compared to known Cu(II)-thiolate and Cu(II)-alkylperoxo complexes from the literature, we found an increased σ interaction in the Cu(II)-OR bond that results in the spectroscopic features. These insights lay the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations. PMID:26907976

  9. Preparation and Basic Properties of BaTiO3-BaPbO3 Multilayer Thin Films by Metal-Alkoxides Method

    Science.gov (United States)

    Azuma, Takahiro; Takahashi, Sheiji; Kuwabara, Makoto

    1993-09-01

    Preferentially oriented barium titanate (BTO)-barium metaplumbate (BPO) multilayer thin films were prepared by the metal-alkoxides method on MgO single crystals. The BPO layer is an electrode for the BTO layer. Thin films were deposited on cleaved MgO (100) substrates by spin coating. A BTO film of 0.4 μm thickness on the BPO layer shows a dielectric constant of about 400 at room temperature. No formation of reaction phases between BTO and BPO, fired at 800°C to yield a well-crystallized BTO film, was detected in X-ray diffraction analysis.

  10. To Evaluate the Application of Alkoxide Sol-Gel Method in Fabrication of 3YSZ-MWCNTs Nanocomposites, in an Attempt to Improve Its Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Ali Ahmadi

    2014-01-01

    Full Text Available In the present research work, fabrication of YSZ-CNTs composite system through alkoxide sol-gel processing was evaluated, in an attempt to improve its mechanical properties. Nanocomposites containing 0.5–2 wt% MWCNTs were then fabricated through the hydrolysis and condensation processing of the solution mixtures containing alkoxide and inorganic precursors along with the functionalized CNTs under basic condition and its final sintering by the SPS technique at 1400°C. Results showed the formation of a nanocomposite powder based on pure 3YSZ matrix, with well dispersion of CNTs and its good adhesion to the matrix particles in composite containing 0.5 wt% CNTs. The fracture toughness of sintered samples showed around 24% increase for the composite containing 0.5 wt% CNTs. The fracture toughness, hardness, and density decreased due to the agglomeration of CNTs over 0.5 wt%. Toughening mechanisms including pullout and crack bridging were observed on the polished and fractured surfaces.

  11. I. Synthesis and characterization of volatile uranium(V) and uranium(VI) alkoxides. II. Isotope selective infrared photochemistry of uranium(VI) hexamethoxide

    International Nuclear Information System (INIS)

    I. A number of uranium(V) and uranium(VI) alkoxides were prepared and characterized, with particular attention to volatility and vibrational spectroscopy. Volatility data and x-ray crystallography implied the uranium(V) complexes to be associated as dimers or higher polymers. The uranium(VI) alkoxides were determined to be monomeric through similar considerations. A detailed discussion of uranium hexamethoxide vibrational data is given, with regard to its suitability for infrared laser photolysis with a CO2-TEA laser. II. Infrared laser photolysis of uranium hexamethoxide was shown to selectively dissociate the 238U containing species, when irradiated with a CO2-TEA laser. Wavelength and fluence dependencies were measured, yielding an optimum 235U enrichment factor (for the unreacted material) of 1.0335 on the P(38)/10.6 μ laser transition at 3.2 J/cm2. A selectivity of 1.5 was calculated from dissociation yield experiments. The photolysis products were analyzed, and the initial reaction was determined to be methoxy radical elimination. Secondary reaction products, in the form of polymethoxy ethers, appear to be the result of intramolecuar reactions (on the uranium substrate) initiated by collisional processes. Several mechanisms are proposed

  12. Kinetic Studies of the Ring-Opening Bulk Polymerization of ɛ-Caprolactone Using a Novel Tin(II) Alkoxide Initiator

    Science.gov (United States)

    Kleawkla, Achara; Suksomran, Wallika; Charuchinda, Anodar; Molloy, Robert; Naksata, Wimol; Punyodom, Winita

    A novel initiator, tin(II) hexoxide, has been synthesized for use in the bulk ring-opening polymerization of ɛ-caprolactone at 140 °C and the kinetics studied using dilatometry. The effectiveness of the new initiator was compared alongside that of the corresponding conventional system, tin(II) octoate / 1-hexanol. The results showed that tin(II) hexoxide, although effective, took time to dissolve in the monomer due to its molecular aggregation, leading to a prolonged induction period. Despite this, first-order kinetics, a high conversion (>90%) and a polycaprolactone (PCL) molecular weight sufficiently high for melt processing were obtained. The small-scale melt spinning of PCL monofilament fibers and the effect of off-line drawing on their tensile properties is also briefly described. This work highlights the potential for the further development of more soluble tin(II) alkoxides for use as initiators which can offer greater reaction control in cyclic ester polymerization.

  13. Fluorinated Alkoxide-Based Magnesium-Ion Battery Electrolytes that Demonstrate Li-Ion-Battery-Like High Anodic Stability and Solution Conductivity.

    Science.gov (United States)

    Crowe, Adam J; Stringham, Kyle K; Bartlett, Bart M

    2016-09-01

    Based on DFT predictions, a series of highly soluble fluorinated alkoxide-based electrolytes were prepared, examined electrochemically, and reversibly cycled. The alcohols react with ethylmagnesium chloride to generate a fluoroalkoxy-magnesium chloride intermediate, which subsequently reacts with aluminum chloride to generate the electrolyte. Solutions starting from a 1,1,1,3,3,3-hexafluoro-2-methylpropan-2-ol precursor exhibit high anodic stability, 3.2 V vs Mg(2+/0), and a record 3.5 mS/cm solution conductivity. Excellent galvanostatic cycling and capacity retention (94%) is observed with more than 300 h of cycle time while employing the standard Chevrel phase-Mo6S8 cathode material.

  14. Synthesis and structural properties of ultra-small oxide (TiO2, ZrO2, SnO2) nanoparticles prepared by decomposition of metal alkoxides

    International Nuclear Information System (INIS)

    The decomposition of metal (Ti, Zr, Sn) alkoxides at 250 deg. C in a solution of tetradecene and dodecylamine resulted in the formation of ultra-small (1-2 nm) oxide nanoparticles. The nanoparticles showed unusual structural properties. The high-pressure orthorhombic phase was found for SnO2. The as-synthesized ZrO2 nanoparticles were only partially crystallized. It was possible to observe their in situ crystallization under the TEM beam. The TiO2 nanoparticles appeared amorphous, with only a few nanocrystals dispersed in the sample. The temperature evolution of the samples was investigated in situ by Raman spectroscopy. All SnO2 was converted to stable cassiterite at 350 deg. C. TiO2 and ZrO2 samples displayed phase stability reversal over a broad range of temperatures.

  15. Synthesis of a mononuclear, non-square-planar chromium(ii) bis(alkoxide) complex and its reactivity toward organic carbonyls and CO2.

    Science.gov (United States)

    Yousif, Maryam; Cabelof, Alyssa C; Martin, Philip D; Lord, Richard L; Groysman, Stanislav

    2016-06-14

    In this paper, we report the synthesis and reactivity of a rare mononuclear chromium(ii) bis(alkoxide) complex, Cr(OR')2(THF)2, that is supported by a new bulky alkoxide ligand (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide). The complex is prepared by protonolysis of square-planar Cr(N(SiMe3)2)2(THF)2 with HOR'. X-ray structure determination disclosed that Cr(OR')2(THF)2 features a distorted seesaw geometry, in contrast to nearly all other tetra-coordinate Cr(ii) complexes, which are square-planar. The reactivity of Cr(OR')2(THF)2 with aldehydes, ketones, and carbon dioxide was investigated. Treatment of Cr(OR')2(THF)2 with two equivalents of aromatic aldehydes ArCHO (ArCHO = benzaldehyde, 4-anisaldehyde, 4-trifluorbenzaldehyde, and 2,4,6-trimethylbenzaldehyde) leads cleanly to the formation of Cr(iv) diolate complexes Cr(OR')2(O2C2H2Ar2) that were characterized by UV-vis and IR spectroscopies and elemental analysis; the representative complex Cr(OR')2(O2C2H2Ph2) was characterized by X-ray crystallography. In contrast, no reductive coupling was observed for ketones: treatment of Cr(OR')2(THF)2 with one or two equivalents of benzophenone forms invariably a single ketone adduct Cr(OR')2(OCPh2) which does not react further. QM/MM calculations suggest the steric demands prevent ketone coupling, and demonstrate that a mononuclear Cr(iii) bis-aldehyde complex with partially reduced aldehydes is sufficient for C-C bond formation. The reaction of Cr(OR')2(THF)2 with CO2 leads to the insertion of CO2 into a Cr-OR' bond, followed by complex rearrangement to form a diamagnetic dinuclear paddlewheel complex Cr2(O2COR')4(THF)2, that was characterized by NMR, UV-vis, and IR spectroscopy, and X-ray crystallography. PMID:27073074

  16. Integration of molecular-layer-deposited aluminum alkoxide interlayers into inorganic nanolaminate barriers for encapsulation of organic electronics with improved stress resistance

    Energy Technology Data Exchange (ETDEWEB)

    Hossbach, Christoph, E-mail: christoph.hossbach@tu-dresden.de; Fischer, Dustin; Albert, Matthias; Bartha, Johann W. [Institute of Semiconductor and Microsystems Technology, Technische Universität Dresden, 01187 Dresden (Germany); Nehm, Frederik, E-mail: frederik.nehm@iapp.de; Klumbies, Hannes; Müller-Meskamp, Lars; Leo, Karl [Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden (Germany); Singh, Aarti; Richter, Claudia; Schroeder, Uwe; Mikolajick, Thomas [Nanoelectronics Materials Laboratory NaMLab gGmbH, Nöthnitzer Str. 64, 01187 Dresden (Germany)

    2015-01-15

    Diffusion barrier stacks for the encapsulation of organic electronics made from inorganic nanolaminates of Al{sub 2}O{sub 3} and TiO{sub 2} with aluminum alkoxide interlayers have been deposited by atomic layer deposition (ALD) and molecular layer deposition (MLD). As a part of the MLD process development, the deposition of aluminum alkoxide with low a density of about 1.7 g/cm{sup 3} was verified. The ALD/MLD diffusion barrier stack is meant to be deposited either on a polymer film, creating a flexible barrier substrate, or on top of a device on glass, creating a thin-film encapsulation. In order to measure the water vapor transmission rate (WVTR) through the barrier, the device is replaced by a calcium layer acting as a water sensor in an electrical calcium test. For the barrier stack applied as thin-film encapsulation on glass substrates, high resolution scanning electron microscopy investigations indicate that the inorganic nanolaminates without MLD interlayers are brittle as they crack easily upon the stress induced by the corroding calcium below. The introduction of up to three MLD interlayers of 12 nm each into the 48 nm barrier film laminate successfully mitigates stress issues and prevents the barrier from cracking. Using the three MLD interlayer configurations on glass, WVTRs of as low as 10{sup −5} g/m{sup 2}/d are measured at 38 °C and 32% relative humidity. On polymer barrier substrates, the calcium is evaporated onto the barrier stack and encapsulated with a cavity glass. In this configuration, the corroding calcium has space for expansion and gas release without affecting the underlying barrier film. In consequence, a WVTR of about 3 × 10{sup −3} g/m{sup 2}/d is measured for all samples independently of the number of MLD interlayers. In conclusion, a stabilization and preservation of the ALD barrier film against mechanical stress is achieved by the introduction of MLD interlayers into the inorganic nanolaminate.

  17. Synthesis of a mononuclear, non-square-planar chromium(ii) bis(alkoxide) complex and its reactivity toward organic carbonyls and CO2.

    Science.gov (United States)

    Yousif, Maryam; Cabelof, Alyssa C; Martin, Philip D; Lord, Richard L; Groysman, Stanislav

    2016-06-14

    In this paper, we report the synthesis and reactivity of a rare mononuclear chromium(ii) bis(alkoxide) complex, Cr(OR')2(THF)2, that is supported by a new bulky alkoxide ligand (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide). The complex is prepared by protonolysis of square-planar Cr(N(SiMe3)2)2(THF)2 with HOR'. X-ray structure determination disclosed that Cr(OR')2(THF)2 features a distorted seesaw geometry, in contrast to nearly all other tetra-coordinate Cr(ii) complexes, which are square-planar. The reactivity of Cr(OR')2(THF)2 with aldehydes, ketones, and carbon dioxide was investigated. Treatment of Cr(OR')2(THF)2 with two equivalents of aromatic aldehydes ArCHO (ArCHO = benzaldehyde, 4-anisaldehyde, 4-trifluorbenzaldehyde, and 2,4,6-trimethylbenzaldehyde) leads cleanly to the formation of Cr(iv) diolate complexes Cr(OR')2(O2C2H2Ar2) that were characterized by UV-vis and IR spectroscopies and elemental analysis; the representative complex Cr(OR')2(O2C2H2Ph2) was characterized by X-ray crystallography. In contrast, no reductive coupling was observed for ketones: treatment of Cr(OR')2(THF)2 with one or two equivalents of benzophenone forms invariably a single ketone adduct Cr(OR')2(OCPh2) which does not react further. QM/MM calculations suggest the steric demands prevent ketone coupling, and demonstrate that a mononuclear Cr(iii) bis-aldehyde complex with partially reduced aldehydes is sufficient for C-C bond formation. The reaction of Cr(OR')2(THF)2 with CO2 leads to the insertion of CO2 into a Cr-OR' bond, followed by complex rearrangement to form a diamagnetic dinuclear paddlewheel complex Cr2(O2COR')4(THF)2, that was characterized by NMR, UV-vis, and IR spectroscopy, and X-ray crystallography.

  18. Epitaxial growth of BaZrO{sub 3} films on single crystal oxide substrates using sol-gel alkoxide precursors

    Energy Technology Data Exchange (ETDEWEB)

    Paranthaman, M.; Shoup, S.S.; Beach, D.B.; Williams, R.K.; Specht, E.D. [Oak Ridge National Lab., TN (United States)

    1997-12-01

    Epitaxial BaZrO{sub 3} (barium zirconium oxide) films were grown on single crystal substrates. A BaZrO{sub 3} precursor solution was prepared by sol-gel synthesis using an all-alkoxide route. The barium precursors were prepared by reacting barium metal with 2-methoxyethanol, and zirconium precursors were prepared by exchanging ligands between zirconium n-propoxide and 2-methoxyethanol. The resulting BaZrO{sub 3} precursor solution was partially hydrolyzed and spin-coated on sapphire (100), SrTiO{sub 3} (strontium titanium oxide) (100), and LaAlO{sub 3} (lanthanum aluminum oxide) (100) substrates. The films were post-annealed in oxygen at 800 C for 2 min in a rapid thermal annealer. The coating and the annealing procedures were repeated three times to obtain the desired thickness, 300 nm. X-ray diffraction studies showed the presence of a single (100) cube texture for BaZrO{sub 3} films on SrTiO{sub 3} and LaAlO{sub 3} substrates. The BaZrO{sub 3} films grown on sapphire had a random texture. The BaZrO{sub 3} films grown on SrTiO{sub 3} substrates had a sharp texture compared to that on LaAlO{sub 3} substrates. This may be due to the relatively smaller lattice mismatch between SrTiO{sub 3} and BaZrO{sub 3}.

  19. Thermal Stability of Neodymium Aluminates High-κ Dielectric Deposited by Liquid Injection MOCVD Using Single-Source Heterometallic Alkoxide Precursors

    Directory of Open Access Journals (Sweden)

    P. Taechakumput

    2012-01-01

    Full Text Available Thin films of neodymium aluminate (NdAlOx have been deposited by liquid injection metalorganic chemical vapor deposition (MOCVD using the bimetallic alkoxide precursor [NdAl(OPri6(PriOH]2. The effects of high-temperature postdeposition annealing on NdAlOx thin films are reported. The as-deposited thin films are amorphous in nature. X-ray diffraction (XRD and medium energy ion scattering (MEIS show, respectively, no crystallization or interdiffusion of metal ions into the substrate after annealing at 950°C. The capacitance-voltage (C-V and current-voltage (I-V characteristics of the thin films exhibited good electrical integrity following annealing. The dielectric permittivity (κ of the annealed NdAlOx was 12, and a density of interface states at flatband (Dit of 4.01×1011  cm−2 eV−1 was measured. The deposited NdAlOx thin films are shown to be able to endure high-temperature stress and capable of maintaining excellent dielectric properties.

  20. 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.

  1. 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

    OpenAIRE

    Alexandre C. de Freitas; Kátia C. M. Westrup; Nunes, Giovana G.; Denis J. Gulin; Haiduke, Roberto L. A.; Jaísa F. Soares; Eduardo L. de Sá

    2010-01-01

    The thermochromic behavior exhibited by vanadium(IV) alkoxides, [V2(μ-OPr i)2(OPr i) 6] and [V2(μ-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 [V2(μ-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 (< 210 K), while spectra recorded at h...

  2. 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

    2016-04-01

    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. PMID:26960813

  3. 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

  4. MgAl2O4 Ultrafiltration Ceramic Membrane Derived from Mg-Al Double Alkoxide%铝镁双醇盐制备MgAl2O4尖晶石陶瓷超滤膜

    Institute of Scientific and Technical Information of China (English)

    张国昌; 陈运法; 吴振江; 谢裕生

    2000-01-01

    Spinel (MgAl2O4) ultrafiltration membranes were prepared on porous α-Al2O3 plates via the sol-gel route. Mg-Al double alkoxide [MgAl2(iprO)s] was first synthesized as the precursor, then hydrolyzed and peptized in aqueous solution. The gel layer was coated from the colloidal sol on the intermediate layer (α-Al2O3), which was formerly prepared to modify the porous substrate, and then thermally treated at 900℃. The processing parameters such as pH, temperature and sol composition during the sol preparation were optimized for controlling particle size. The pore size of the 2μm thick top layer is about 13 nm as estimated by both the BSA (Bovine Serum Albumin)retention test and an empirical equation.The water permeability of the obtained spinel membrane is 55~143 kg/(min.cm2.Pa).

  5. 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.

  6. 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

  7. 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

  8. Characteristics of tetrahydrofuran-based electrolytes with magnesium alkoxide additives for rechargeable magnesium batteries

    Science.gov (United States)

    Kim, In-Tae; Yamabuki, Kazuhiro; Sumimoto, Michinori; Tsutsumi, Hiromori; Morita, Masayuki; Yoshimoto, Nobuko

    2016-08-01

    The electrochemical behavior of magnesium (Mg) metal was investigated in tetrahydrofuran (THF)-based solutions containing magnesium bromide (MgBr2) and/or magnesium ethoxide (Mg(OEt)2). THF solutions containing a single solute, MgBr2 or Mg(OEt)2, show no visible faradaic current based on Mg deposition and/or dissolution. However, the electrolyte system containing both solutes, MgBr2 + Mg(OEt)2/THF, gives a reversible current response of Mg deposition and dissolution. The ionic structure of the electrolyte system containing the binary solute was examined by infrared (IR) spectroscopy and density functional theory (DFT) calculations. It was confirmed that MgBr2 and Mg(OEt)2 are coordinated (solvated) with THF molecules to form an EtOsbnd Mgsbnd Br·4THF complex. The DFT calculations also suggest the possible formation of μ-complexes for the MgBr2/Mg(OEt)2 binary system in THF. The voltammetric responses at the Pt electrode indicate low overpotential and high coulombic efficiency for Mg deposition and dissolution in THF-based solutions containing suitable molar ratios of MgBr2 and Mg(OEt)2. The constant-current charge-discharge cycling of Mg in MgBr2 + Mg(OEt)2/THF electrolyte also shows low overpotential and good cyclability over 300 cycles.

  9. Synthesis of Yttria-Stabilized Zirconia Aerogels by a Non-Alkoxide Sol-Gel Route

    Energy Technology Data Exchange (ETDEWEB)

    Chervin, C N; Clapsaddle, B J; Chiu, H W; Gash, A E; Satcher, Jr., J H; Kauzlarich, S M

    2005-02-11

    Homogeneous, nanocrystalline powders of yttria-stabilized zirconia were prepared using a nonalkoxide sol-gel method. Monolithic gels, free of precipitation, were prepared by addition of propylene oxide to aqueous solutions of Zr{sup 4+} and Y{sup 3+} chlorides at room temperature. The gels were dried with supercritical CO{sub 2}(l), resulting in amorphous aerogels that crystallized into cubic stabilized ZrO{sub 2} following calcination at 500 C. The aerogels and resulting crystalline products were characterized using in-situ temperature profile X-ray diffraction, thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. TEM and N{sub 2} adsorption/desorption analysis of an aerogel indicated a porous network structure with a high surface area (409 m{sup 2}/g). The crystallized yttria-stabilized zirconia maintained high surface area (159 m{sup 2}/g) upon formation of homogeneous, nanoparticles ({approx}10 nm). Ionic conductivity at 1000 C of sintered YSZ (1500 C, 3 hours) prepared by this method, was 0.13 {+-} 0.02 {Omega}{sup -1} cm{sup -1}. Activation energies for the conduction processes from 1000-550 C and 550-400 C, were 0.95 {+-} 0.09 and 1.12 {+-} 0.05 eV, respectively. This is the first reported synthesis and characterization of yttria-stabilized zirconia via an aerogel precursor.

  10. Hafnium oxide gate dielectrics grown from an alkoxide precursor: structure and defects

    International Nuclear Information System (INIS)

    We present an infrared spectroscopy and X-ray diffraction study of hafnium oxide gate dielectric films deposited from hafnium tetra-tert-butoxide, Hf(OC(CH3)3)4. We characterize the crystal phase as a function of thickness and detect the chemical state of impurities in this high-permittivity (high-κ) material. The HfO2 films are composed of monoclinic crystallites in an amorphous matrix. The crystalline fraction increases with increasing film thickness. Infrared spectroscopy is used to obtain information about impurities, which may help to uncover the nature of electrical defects. We detect and quantify for instance the presence of incorporated hydroxyl groups or water that may be responsible for the deviation from ideal HfO2 stoichiometry. The concentration of residual C-H bonds is low. However, carbon is incorporated in an oxidized form, possibly as carbonate

  11. Preparation of titanium diboride powders from titanium alkoxide and boron carbide powder

    Indian Academy of Sciences (India)

    Hamed Sinaei Pour Fard; Hamidreza Baharvandi

    2011-07-01

    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 of TTIP solution, 0.033/0.05/0.1, were prepared and the molar ratio of B4C to TTIP varied from 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 1200°C.

  12. Electrochemical Synthesis of Lead Alkoxide Complexes%铅醇盐配合物的电化学合成

    Institute of Scientific and Technical Information of China (English)

    朱传高; 王凤武; 朱琼霞

    2006-01-01

    在无隔膜电解槽中,电化学溶解铅金属制备铅醇盐配合物Pb(OEt)4、Pb(OBu)4、Pb(OCH2CH2-OCH3)4、Pb(OEt)2(acac)2、Pb(OBu)2(acac)2、Pb(OCH2CH2OCH3)2(acac)2[acac-为乙酰丙酮基]. 产物通过红外光谱(FT-IR)、拉曼光谱和核磁共振测试技术进行表征. 实验表明,采用有机胺溴化物为导电盐,可以防止阳极钝化,提高电合成效率;电解合成Pb(OCH2CH2OCH3)4、Pb(OEt)2(acac)2、Pb(OBu)2(acac)2、Pb(OCH2CH2OCH3)2(acac)2有较高的电流效率和产率.

  13. 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.

  14. Non-oxo vanadium(IV) alkoxide chemistry: solid state structures, aggregation equilibria and thermochromic behaviour in solution.

    Science.gov (United States)

    Westrup, Kátia C M; Gregório, Thaiane; Stinghen, Danilo; Reis, Dayane M; Hitchcock, Peter B; Ribeiro, Ronny R; Barison, Andersson; Back, Davi F; de Sá, Eduardo L; Nunes, Giovana G; Soares, Jaísa F

    2011-04-01

    The reversible thermochromic behaviour of homoleptic [{V(OR)(4)}(n)] complexes in solution [R = Pr(i) (product I), Bu(s) (B(s)), Nep (N) and Cy (C)] is accounted for the existence of an aggregation equilibrium involving dimeric and monomeric species in which vanadium(iv) is respectively five- and four-coordinate. Bulky R groups such as Bu(t) and Pe(t) (tert-pentoxide) prevent aggregation and therefore give rise to exclusively mononuclear compounds (B(t) and P(t), respectively) that are not thermochromic. The complexes and their temperature-dependent interconversion were characterised by single crystal X-ray diffractometry, magnetic susceptibility measurements and electronic, FTIR and EPR spectroscopies in a wide temperature range. Equilibrium constants and enthalpy and entropy changes for the dimerization reactions have been determined and compared with literature data. PMID:21347465

  15. Characterization of the alkoxide-based sol-gel derived La9.33Si6O26 powder and ceramic.

    Science.gov (United States)

    Vojisavljević, Katarina; Chevreux, Pierrick; Jouin, Jenny; Malič, Barbara

    2014-01-01

    In this study, we report on the acid-catalysed synthesis of La(9.33)Si(6)O(26) from lanthanum nitrate or acetate and silicon ethoxide (TEOS) in the ethanol solvent, upon the transition from liquid to amorphous and crystalline phases. The similarity of the Fourier transform infrared spectra of the lanthanum-salt solutions and lanthanum-silicon sols indicates that the lanthanum environment is not changed in the reaction of the La-salt with TEOS. In the nitric-acid catalysed synthesis, the hydrolysis reaction was almost instantaneous, as a consequence of a higher amount of water in this system, which contributed to a high level of chemical heterogeneity in the product. The acetic acid-based synthesis ensured a good mixing of the reagents at the nanometre level, which gave rise to the formation of the pure La(9.33)Si(6)O(26) powder upon heating at 900 °C, and single phase ceramics with 94 % relative density after sintering at 1400 °C for 3 h in air, which is 200 °C lower temperature then usually reported for the apatite material. PMID:25286208

  16. 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.

  17. Hydrate and alkoxide forms of molybdophosphoric heteropoly acid and specific features of their formation under conditions of isothermal absorption of water, methanol, and ethanol vapors

    International Nuclear Information System (INIS)

    By the gravimetry method it was ascertained that interaction of vapors of water, methanol and ethanol with solid molybdophosphoric acid at room temperature is accompanied by formation of volumetric hydrates and alcoholates proceeding in several stages, clearly defined during isotherm recording under sorption and desorption conditions. Formation of alcoholates gives rise to loosening of the acid lattice, which dictates largely more active absorption of alcohols at the first stages of sorption compared with water and, when the compositions H3PMo12O40 · 11.5 CH3OH and H3PMo12O40 · 14.7 C2H5OH is attained, it results in their liquefying

  18. 石膏用甲基硅醇钾改性丙烯酸酯涂料%Acrylate Coatings Modified by Potassium Methane-siliconic Alkoxide Used on Plasterboard

    Institute of Scientific and Technical Information of China (English)

    杨波; 刘东辉; 张健

    2005-01-01

    通过甲基硅醇钾和丙烯酸酯的共聚反应,制得具有良好防水性乳液型石膏用涂料,其引发剂(过硫酸钾)用量为0.95%时,石膏板2h吸水率为2.23%;甲基硅醇钾用量为9.56%时,石膏板耐沾污性良好,用量为8.27%、8.40%时,耐油污性能良好.

  19. EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol-gel generated Mg-Al-CO3 layered double hydroxide with very labile interlayer anions

    NARCIS (Netherlands)

    Chubar, N.

    2014-01-01

    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

  20. Structure-reactivity relationships in aluminium alkoxides-catalysed co-polymerisation reactions : aluminium 2,2' methylenebisphenoxide in the synthesis of poly(ether-carbonate)s from cyclohexene oxide and carbon dioxide

    OpenAIRE

    Sypien, Jakub Konrad

    2006-01-01

    Das Design und die Synthese von "Single-Site"-Katalysatoren für die Copolymerisierung von Kohlendioxids und Cyclohexenoxid (CHO), Untersuchungen zu ihrer Struktur-Reaktivitätsbeziehung sowie die Optimierung der Reaktionsparameter waren Hauptaugenmerk dieser Arbeit. Die Liganden für das Katalysator-Design beruhen auf 2,2'-Bisphenol-Derivaten, entweder Methylen- (1-6 basierte Systeme) oder Sulfid-verbrückt (7 basierte Systeme). Die meisten der verwendeten Liganden wurden bereits in der Literatu...

  1. POLYMETALLIC CHROMIUM ALKOXIDES - SYNTHESIS AND CRYSTAL-STRUCTURES OF (I-PRO)8CR2NA4(THF)4 AND (MU-3-OPH)10CR4(MU-3-O)3NA4(TMEDA)4

    NARCIS (Netherlands)

    EDEMA, JJH; GAMBAROTTA, S; SMEETS, WJJ; SPEK, AL

    1991-01-01

    The reaction of (RO)8Cr2Na4(THF)4[R = i-Pr (1a), Ph (1b)] with TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine) has been studied. While the isopropyl derivative 1a yielded the polymeric [(i-PrO)2Cr]n, in the case of 1b, the Cr(III) aggregate (PhO)10Cr4(mu-3-O)3Na4(TMEDA)4 (2) was formed via an u

  2. I. Synthesis and characterization of volatile uranium(VI) alkoxides for laser-induced uranium isotope separation. II. Synthesis and characterization of octaalkyl metallo and metal-free phthalocyanines, decaalkyl uranyl superphthalocyanines, and hemiporphyrazines

    International Nuclear Information System (INIS)

    Current efforts in laser-induced U isotope separation with emphasis on the synthesis of volatile U complexes suitable for selective multiphoton infrared excitation with a CO2 laser are discussed. Efficient one-step scalable syntheses of U hexamethoxide, U(OCH3)6, starting from the readily available UF6 and NaOCH3 or CH3Si(OCH3)3 are described. The solution phase electronic spectrum of U(OCH3)6 is interpreted in terms of both ligand- and solvent-to-metal charge transfer. The vibrational spectroscopy of U(OCH3)6 in solution and in the solid state is described, and the spectroscopic results for the complex in the 10 m region are presented and discussed in terms of the observed laser-induced photochemistry of U(OCH3)6. The vapor pressure of U(OCH3)6 was found to be 3 μ at 190C, increasing to 17 μ at 330C. The heat of sublimation, ΔH/sub '/, and entropy of sublimation, ΔS/sub '/, were meaured as 19 +- 4 kcal/mole and 58+-7 eu, respectively. A straightforward, efficient, and generalizable synthesis of symmetrically substituted 2,3,9,10,16,17,23,23-octaalkyl phthalocyanines and 2,3,9,10,16,17,23,24,30,31-decaalkyl uranyl superphthalocyanines from o-dialkyl benzenes is described. The synthesis is illustrated with methyl and n-butyl substituents, and the complexes are characterized by a variety of chemical and physiochemical methods. The preparation of other U complexes and of a macrocyclic compound that undergoes a metalation reaction with activated Ti, activated Mg, n-BuLi, and Li-di-tert-butylphenyl are described in 4 appendixes

  3. Inherent substrate-dependent growth initiation and selective-area atomic layer deposition of TiO{sub 2} using “water-free” metal-halide/metal alkoxide reactants

    Energy Technology Data Exchange (ETDEWEB)

    Atanasov, Sarah E.; Kalanyan, Berç; Parsons, Gregory N., E-mail: gnp@ncsu.edu [Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905 (United States)

    2016-01-15

    Titanium dioxide atomic layer deposition (ALD) is shown to proceed selectively on oxidized surfaces with minimal deposition on hydrogen-terminated silicon using titanium tetrachloride (TiCl{sub 4}) and titanium tetra-isopropoxide [Ti(OCH(CH{sub 3}){sub 2}){sub 4}, TTIP] precursors. Ex situ x-ray photoelectron spectroscopy shows a more rapid ALD nucleation rate on both Si–OH and Si–H surfaces when water is the oxygen source. Eliminating water delays the oxidation of the hydrogen-terminated silicon, thereby impeding TiO{sub 2} film growth. For deposition at 170 °C, the authors achieve ∼2 nm of TiO{sub 2} on SiO{sub 2} before substantial growth takes place on Si–H. On both Si–H and Si–OH, the surface reactions proceed during the first few TiCl{sub 4}/TTIP ALD exposure steps where the resulting products act to impede subsequent growth, especially on Si–H surfaces. Insight from this work helps expand understanding of “inherent” substrate selective ALD, where native differences in substrate surface reaction chemistry are used to promote desired selective-area growth.

  4. Supercritical carbon dioxide, a tool for the dispersion ROP of lactone and PCL foaming: Part A

    OpenAIRE

    Grignard, Bruno; Urbanczyk, Laetitia; Stassin, Fabrice; Calberg, Cédric; Detrembleur, Christophe; Jérôme, Christine

    2008-01-01

    Aliphatic polyesters, namely polylactide (PLA) and poly-ε-caprolactone (PCL) are biodegradable and biocompatible materials that find applications as resorbable suture (PLA) and drugs delivery vectors (PCL). Nevertheless, these polymers were mainly prepared by ring opening polymerization using aluminum alkoxide or tin alkoxide initiators in organic media. Recently, the use of supercritical carbon dioxide as polymerization medium was proposed as a potential alternative to the use toxic organic ...

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

    OpenAIRE

    García-Heras, M.; González-Mena, E.; Villegas, M. A.

    2004-01-01

    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 s...

  6. 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.

  7. 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.

  8. Single-step synthesis of well-crystallized and pure barium titanate nanoparticles in supercritical fluids

    Science.gov (United States)

    Reverón, Helen; Aymonier, Cyril; Loppinet-Serani, Anne; Elissalde, Catherine; Maglione, Mario; Cansell, François

    2005-08-01

    Single-step synthesis of ultra-fine barium titanate powder with a crystallinity as high as 90% and without barium carbonate contamination has been successfully performed under supercritical conditions using a continuous-flow reactor in the temperature range 150-380 °C at 16 MPa. To synthesize this bimetallic oxide, alkoxides, ethanol and water were used. The influence of the synthesis parameters on the BaTiO3 powder characteristics was investigated. The results show that the water to alkoxide precursor ratio, the reactor temperature and the Ba:Ti molar ratio of alkoxide precursor play a major role in the crystallization of pure and well-crystallized BaTiO3 nanoparticles. The continuous mode of operation without post-treatments for powder washing, drying or crystallization increase the industrial interest.

  9. Homochiral metal complexes for biodegradable polymer synthesis

    OpenAIRE

    Buffet, Jean-Charles

    2010-01-01

    Chapter One introduces the principle of alkoxide and phosphine oxide as ligands for lanthanides and electropositive metals, ligand self-recognition, stereoselective polymerisation of lactide, fixation of CO2 and finally copolymerisation of CO2 and epoxide. Chapter Two shows the synthesis of the proligands rac-HLR (a racemic phosphine oxide-alkoxide, A, where R = tBu, Ph or C6H3-Me-3,5) and explores the resolution into diastereomeric RRR- and SSS-M(LR)3 to afford C3–symmetric...

  10. Regioselective, Transition Metal-Free C-O Coupling Reactions Involving Aryne Intermediates.

    Science.gov (United States)

    Dong, Yuyang; Lipschutz, Michael I; Tilley, T Don

    2016-04-01

    A new transition-metal-free synthetic method for C-O coupling between various aryl halides and alkoxides is described. This type of transformation is typically accomplished using palladium catalysts containing a specialized phosphine ligand. The reactions reported here can be performed under mild, ambient conditions using certain potassium alkoxides and a range of aryl halides, with iodide and bromide derivatives giving the best results. A likely mechanistic pathway involves the in situ generation of an aryne intermediate, and directing groups on the aryl ring inductively control regioselectivity.

  11. Effect of Mixing and Other Operating Parameters in Sol-Gel Processes

    OpenAIRE

    Marchisio, Daniele L.; Omegna, Federica; Barresi, Antonello A.; Bowen, Paul

    2008-01-01

    In this work the effect of mixing on a sol-gel process is quantitatively investigated. Titanium dioxide synthesis from titanium tetra-isopropoxide is used as a test reaction. Solutions of titanium alkoxide in isopropyl alcohol and water in isopropyl alcohol are mixed in a special mixing device (i.e., vortex reactor) at different mixing rates, and the effect of mixing is quantified and compared with the effect of the other relevant operating parameters, namely the water to alkoxide, acid to a...

  12. 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...

  13. 合成钛硅分子筛TS-1的一种新方法%A NOVEL METHOD FOR SYNTHESIS OF TS-1

    Institute of Scientific and Technical Information of China (English)

    周继承; 王祥生

    1999-01-01

    @@ In both conventional method[1] and modified method[2] ,organic Si and Ti alkoxides were used as Si source and Ti source respectively, and only strong organic base was used. So this system may be called as organic synthesis one (see Fig 1 )Thangaraj et al[3] reported that in the organic synthesis system only organic strong base TPAOH can be used.

  14. Some Remarks on Asymmetric Syntheses from Recent Studies

    OpenAIRE

    Baba, Naomichi

    1990-01-01

    Some asymmetric syntheses were presented here and discussed briefly including NADH model reactions, phase transfer-catalyzed asymmetric epoxidation, enantiotopic group-selective hydrolysis of a malonic anhydride with alkoxide anion, intramolecular acid-catalyzed lactonizations, catalytic asymmetric Diels-Alder synthesis, asymmetric aldol condensation, chiral homoallyl alcohol synthesis, asymmetric addition of diethylzinc to aldehyde, kinetic resolution of racemic hydroperoxides and binaphthol...

  15. Tetragonal zirconia: Wet chemical preparation, mechanical and electrical properties

    NARCIS (Netherlands)

    Keizer, K.; Hemert, van M.; Graaf, van de M.A.C.G.; Burggraaf, A.J.

    1985-01-01

    Yttria-stabilized zirconia powders were prepared in the composition range of 3 to 13 at% yttria. The hydrolysis-gel precipitation technique was used, starting from metal alkoxides or chlorides. In the composition range between 5 and 10 at% yttria, the materials sintered at 1250°C have a fully tetrag

  16. 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...

  17. 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...

  18. Effect of grain boundaries on the conductivity of high-purity ZrO2---Y2O3 ceramics

    NARCIS (Netherlands)

    Verkerk, M.J.; Middelhuis, B.J.; Burggraaf, A.J.

    1982-01-01

    Grain boundary conductivities are determined by complex impedance measurements (1–106 Hz) on high-purity ceramics prepared by the alkoxide synthesis and on less pure ceramics obtained from a commercial powder. The grain size was varied systematically in the region 0.36–55 μm. The grain boundary cond

  19. Air/Water-Stable Tridentate NHC-PdII Complex; Catalytic C-H Activation of Hydrocarbons via H/D Exchange Process in D2O

    OpenAIRE

    Lee, Joo Ho; Yoo, Kyung Soo; Park, Chan Pil; Olsen, Janet M.; Sakaguchi, Satoshi; Surya Prakash, G. K.; Mathew, Thomas; Jung, Kyung Woon

    2009-01-01

    While developing novel catalysts for carbon-carbon or carbon-heteroatom coupling (N, O, or F), we were able to introduce tridentate NHC-amidate-alkoxide palladium(II) complexes. In aqueous solution, these NHC-Pd(II) complexes showed high ability for C-H activation of various hydrocarbons (cyclohexane, cyclopentane, dimethyl ether, THF, acetone, and toluene) under mild conditions.

  20. Alcohol dispersions of calcium hydroxide nanoparticles for stone conservation.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Suzuki, Amelia; Ruiz-Agudo, Encarnacion

    2013-09-10

    Alcohol dispersions of Ca(OH)2 nanoparticles, the so-called nanolimes, are emerging as an effective conservation material for the consolidation of stone, mortars, and plasters present in old masonry and/or mural paintings. To better understand how this treatment operates, to optimize its performance and broaden its applications, here we study the nano and microstructural characteristics, carbonation behavior, and consolidation efficacy of colloidal alcohol dispersions of Ca(OH)2 nanoparticles produced by both homogeneous (commercial nanolime) and heterogeneous phase synthesis (aged slaked lime and carbide lime putties). We observe that the alcohol not only provides a high colloidal stability to Ca(OH)2 particles, but also affects the kinetics of carbonation and CaCO3 polymorph selection. This is due to the pseudomorphic replacement of Ca(OH)2 particles by calcium alkoxides upon reaction with ethanol or 2-propanol. The extent of this replacement reaction depends on Ca(OH)2 size and time. Hydrolysis of alkoxides speeds up the carbonation process and increases the CaCO3 yield. The higher degree of transformation into calcium alkoxide of both the commercial nanolime and the carbide lime fosters metastable vaterite formation, while calcite precipitation is promoted upon carbonation of the aged slaked lime due its lower reactivity, which limits calcium alkoxide formation. A higher consolidation efficacy in terms of strength gain of treated porous stone is achieved in the latter case, despite the fact that the carbonation is much faster and reaches a higher yield in the former ones. Formation of alkoxides, which has been neglected in previous studies, needs to be considered when applying nanolime treatments. These results show that the use Ca(OH)2 nanoparticle dispersions prepared with either aged slaked lime or carbide lime putties is an economical and effective conservation alternative to commercial nanolimes produced by homogeneous phase synthesis. Ultimately, this

  1. Activation and deactivation of a robust immobilized Cp*Ir-transfer hydrogenation catalyst: a multielement in situ X-ray absorption spectroscopy study.

    Science.gov (United States)

    Sherborne, Grant J; Chapman, Michael R; Blacker, A John; Bourne, Richard A; Chamberlain, Thomas W; Crossley, Benjamin D; Lucas, Stephanie J; McGowan, Patrick C; Newton, Mark A; Screen, Thomas E O; Thompson, Paul; Willans, Charlotte E; Nguyen, Bao N

    2015-04-01

    A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray absorption spectroscopy (XAS) at Ir L3-edge, Cl K-edge, and K K-edge. These culminate in in situ XAS experiments that link structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and "hot filtration" experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active precatalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide-iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure. PMID:25768298

  2. Application of ethanolamine method for the preparation of indium oxide-based sols and films

    International Nuclear Information System (INIS)

    This paper reports that it is found that ethanolamine method, is very useful to form stable, concentrated (0.4--0.5M) indium oxide-based sols from which very uniform, transparent In2O3 and ITO films are obtained by dip-coating. Indium isopropoxide and acetate can be used as the starting materials. The optical and electrical properties of these films were examined. A transparent ITO film with the highest conductivity (3030 S/cm, after annealing at 0.5 torr--600 degrees C for 60 min) was obtained from the acetate at 600 degrees C. The films from the alkoxide had lower conductivities probably due to the impurities included in the alkoxide

  3. 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.

  4. Synthesis and Crystal Structure of a Tetranuclear Cubane-like Nickel(Ⅱ) Complex with 2-Hydroxymethyl-N-salicylideneaniline

    Institute of Scientific and Technical Information of China (English)

    LIU, Hui-Yan; WANG, Hai-Ying; SHI, Da-Qing; TIAN, Jin-Lei

    2006-01-01

    The tetranuclear cubane-like complex, [NiL(EtOH)]4·0.5EtOH (1) with tridentate Schiff base ligand (H2L=2-Hydroxymethyl-N-salicylideneaniline) has been synthesized and its crystal structure and spectroscopic properties have been studied. The complex consists of a tetranuclear (NiO)4 cubane core, of which four nickel(Ⅱ) ions are bridged by μ3-alkoxide group and each nickel(Ⅱ) ion is coordinated to three ,u3-alkoxide oxygen atoms, one imino nitrogen atom and one phenoxide oxygen atom from Schiff base ligand, and further ligated by one EtOH molecule,completing a distorted octahedral geometry.

  5. Atom economical synthesis of di- and trithiocarbonates by the lithium tert-butoxide catalyzed addition of carbon disulfide to epoxides and thiiranes.

    Science.gov (United States)

    Diebler, J; Spannenberg, A; Werner, T

    2016-08-21

    Alkali metal alkoxides were studied as catalysts for the addition of CS2 to epoxides. A screening of several commercially available alkoxides revealed lithium tert-butoxide as an active and selective catalyst for this reaction. The influence of different reaction parameters as well as the substrate scope under optimized reaction conditions has been studied. Terminal and highly substituted epoxides as well as thiiranes were converted. In total 28 products were prepared and isolated in yields up to 95%. Notably, the reactions were performed under mild conditions without additional solvents. The regio- and stereoselectivity of the reaction has been studied e.g. by converting (R)-styrene and (R)-propylene oxide. Moreover, the test reaction was monitored by (13)C NMR and a plausible mechanism for the conversion of terminal and internal epoxides is given. This proposal is in agreement with the observed regio- and stereoselectivity of the reaction. PMID:27339808

  6. Study of phase transformation and microstructure of alcohol washed titania nanoparticles for thermal stability

    Science.gov (United States)

    Kaur, Manpreet; Singh, Gaganjot; Bimbraw, Keshav; Uniyal, Poonam

    2015-08-01

    Nanostructured titania have been successfully synthesized by hydrolysis of alkoxide at calcination temperatures 500 °C, 600 °C and 700 °C. As the calcination temperature increases, alcohol washed samples show lesser rutile content as compared to water washed samples. Morphology and Particle sizes was determined by field emission scanning electron microscopy (FESEM), while thermogravimetric-differential scanning calorimetry (TG-DSC) was used to determine thermal stability. Alcohol washed samples undergo 30% weight loss whereas 16% in water washed samples was observed. The mean particle sizes were found to be increase from 37 nm to 100.9 nm and 35.3 nm to 55.2 nm for water and alcohol washed samples respectively. Hydrolysis of alkoxide was shown to be an effective means to prepare thermally stable titania by using alcohol washed samples as a precursor.

  7. Study of phase transformation and microstructure of alcohol washed titania nanoparticles for thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Manpreet, E-mail: manpreet.kaur@thapar.edu; Singh, Gaganjot; Bimbraw, Keshav; Uniyal, Poonam, E-mail: uniyalpoonam@gmail.com [School of Physics and Materials Science, Thapar University, Patiala-147 004, Punjab (India)

    2015-08-28

    Nanostructured titania have been successfully synthesized by hydrolysis of alkoxide at calcination temperatures 500 °C, 600 °C and 700 °C. As the calcination temperature increases, alcohol washed samples show lesser rutile content as compared to water washed samples. Morphology and Particle sizes was determined by field emission scanning electron microscopy (FESEM), while thermogravimetric-differential scanning calorimetry (TG-DSC) was used to determine thermal stability. Alcohol washed samples undergo 30% weight loss whereas 16% in water washed samples was observed. The mean particle sizes were found to be increase from 37 nm to 100.9 nm and 35.3 nm to 55.2 nm for water and alcohol washed samples respectively. Hydrolysis of alkoxide was shown to be an effective means to prepare thermally stable titania by using alcohol washed samples as a precursor.

  8. The reaction of yttrium-aluminium garnet with t-zirconia

    International Nuclear Information System (INIS)

    The reaction of 6 mol% Y2O3 stabilized tetragonal zirconia (t-ZrO2) with yttrium-aluminum garnet (Y3Al5O12, YAG) was studied at temperatures between 1200 degrees C and 1625 degrees C. Reaction couples were made from polished 0.2 μm grain size plates of hot-pressed Tosoh TZ-3Y t-ZrO2 with 6 mol% yttria. Some plates were not pressed under vacuum in carbon dies with YAG powder prepared from yttrium and aluminum alkoxides. Other plates were coated with a metal alkoxide derived YAG sol or coated by laser vapor deposition of YAG, and then heat-treated in air in a Netzsch thermogravimetric furnace. The reaction products and microstructures are characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy with energy dispersive spectrometry

  9. LIGAND AND ALKALI-METAL CATION CONTROL ON THE MOLECULAR COMPLEXITY OF ANIONIC CHROMIUM(II) ARYLOXIDES - PREPARATION AND CRYSTAL-STRUCTURE OF DIMERIC (PHO)10CR2LI6(THF)6 AND (2,6-ME2C6H3O)6CR2LI2(THF)4 AND TRIMERIC (GUO)14CR3NA9CL [GUO = (ORTHO-CH3O)C6H4O] WITH AN ENCAPSULATED CHLORIDE-ION

    NARCIS (Netherlands)

    EDEMA, JJH; MEETSMA, A; GAMBAROTTA, S; KHAN, SI; SMEETS, WJJ; SPEK, AL

    1991-01-01

    Two new anionic, dimeric chromium(II) alkoxides, (PhO)10Cr2Li6(THF)6 (3) and (2,6-Me2C6H3O)6Cr2Li2(THF)4 (4), have been prepared and characterized by X-ray structure determination. The two complexes possess similar Cr2(OR)2 cores with a fairly long Cr-Cr distance [Cr...Cr' = 3.149 (2) and 3.091 (1)

  10. Nanocomposite organomineral hybrid materials. Part 2

    OpenAIRE

    KUDRYAVTSEV Pavel Gennadievich; FIGOVSKY Oleg Lvovich

    2016-01-01

    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 t...

  11. Controlled synthesis of fluorescent silica nanoparticles inside microfluidic droplets

    OpenAIRE

    Wacker, Josias Basil; Lignos, Ioannis; Parashar, Virendra Kumar; Gijs, Martinus

    2012-01-01

    We study the droplet-based synthesis of fluorescent silica nanoparticles (50–350 nm size) in a microfluidic chip. Fluorescein-isothiocyanate (FITC) dye is first chemically linked to aminopropyl triethoxysilane (APTES) in ethanol and this reaction product is subsequently mixed with tetraethyl orthosilicate (TEOS) to yield a fluorescent silicon alkoxide precursor solution. The latter reacts with an aqueous ethanol–ammonia hydrolysing mixture inside droplets, forming fluorescent silica nanoparti...

  12. Darstellung lanthanoidhaltiger Oxid- und Hydroxidphasen : neue Konzepte zur Kontrolle von Morphologie und funktionellen Eigenschaften

    OpenAIRE

    Hemmer, Eva

    2008-01-01

    Aufgrund der potentiellen Anwendungen in optischen Bauteilen, als Biomarker oder Kontrastmittel wächst das Interesse an Ln-haltigen nanokristallinen Materialien stetig. Die vorliegende Dissertation beschäftigt sich mit neuen Konzepten zur morphologie- und phasenkontrollierten Synthese von Ln-Oxiden und Hydroxiden. Dazu wurden Ln-Alkoxide mit unterschiedlichen Liganden und Metallkombinationen synthetisiert und ihre Eignung als Vorstufen für die Materialsynthese mittels Solvothermal-, Sol-Gel- ...

  13. Carbon–heteroatom bond formation catalysed by organometallic complexes

    OpenAIRE

    Hartwig, John F.

    2008-01-01

    At one time the synthetic chemist’s last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been ...

  14. Evolution of microstructure in mixed niobia-hybrid silica thin films from sol-gel precursors.

    Science.gov (United States)

    Besselink, Rogier; Stawski, Tomasz M; Castricum, Hessel L; ten Elshof, Johan E

    2013-08-15

    The evolution of structure in sol-gel derived mixed bridged silsesquioxane-niobium alkoxide sols and drying thin films was monitored in situ by small-angle X-ray scattering. Since sol-gel condensation of metal alkoxides proceeds much faster than that of silicon alkoxides, the incorporation of d-block metal dopants into silica typically leads to formation of densely packed nano-sized metal oxide clusters that we refer as metal oxide building blocks in a silica-based matrix. SAXS was used to study the process of niobia building block formation while drying the sol as a thin film at 40-80°C. The SAXS curves of mixed niobia-hybrid silica sols were dominated by the electron density contrast between sol particles and surrounding solvent. As the solvent evaporated and the sol particles approached each other, a correlation peak emerged. Since TEM microscopy revealed the absence of mesopores, the correlation peak was caused by a heterogeneous system of electron-rich regions and electron poor regions. The regions were assigned to small clusters that are rich in niobium and which are dispersed in a matrix that mainly consisted of hybrid silica. The correlation peak was associated with the typical distances between the electron dense clusters and corresponded with distances in real space of 1-3 nm. A relationship between the prehydrolysis time of the silica precursor and the size of the niobia building blocks was observed. When 1,2-bis(triethoxysilyl)ethane was first hydrolyzed for 30 min before adding niobium penta-ethoxide, the niobia building blocks reached a radius of 0.4 nm. Simultaneous hydrolysis of the two precursors resulted in somewhat larger average building block radii of 0.5-0.6 nm. This study shows that acid-catalyzed sol-gel polymerization of mixed hybrid silica niobium alkoxides can be rationalized and optimized by monitoring the structural evolution using time-resolved SAXS.

  15. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

    OpenAIRE

    Banger, Kulbinder K.; Peterson, Rebecca L.; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide ...

  16. A Convenient Method for Asymmetric Reduction of Acetophenone using Lithium Hydroxide

    OpenAIRE

    NISHIKORI, Hisashi; Mizuno, Tomofumi; 錦織, 寿

    2010-01-01

    Optically active lithium-alkoxide catalyzes asymmetric reduction of ketones and imines with alkoxyhydrosilane as a Lewis base. Lithium salt is generally formed by a mixture of optically active alcohol and n-butyllithium as a metal source, which is too sensitive to moisture to handle in air. However, if n-butyllithium is replaced by another lithium source which is stable in air, a more convenient reaction system results. In this study, we examined the enantioselective reduction of acetophenone...

  17. Substrate effect on nanoporous structure of silica wires by channel-confined self-assembly of block-copolymer and sol-gel precursors

    OpenAIRE

    Michael Z. Hu; Peng Lai

    2015-01-01

    Nanoporous silica wires of various wire diameters were developed by space-confined molecular self-assembly of triblock copolymer ethylene/propylene/ethylene (P123) and silica alkoxide precursor (tetraethylorthosilicate, TEOS). Two distinctive hard-templating substrates, anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC), with channel diameters in the range between 10 nm and 200 nm were employed for space-confinement of soft molecular self-assembly driven by the block-copolymer...

  18. Nanocomposite organomineral hybrid materials. Part I

    OpenAIRE

    KUDRYAVTSEV Pavel Gennadievich; FIGOVSKY Oleg Lvovich

    2016-01-01

    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 t...

  19. 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. PMID:26332745

  20. Structure, Mechanism and Applications of Sol-Gel Clad Fiber-Optic Sensors

    OpenAIRE

    Fellows Olteanu, Marta Sarah

    2010-01-01

    Xerogels are porous glasses formed from the hydrolysis and polycondensation of metal alkoxides. Xerogels are used as insulators, catalysts, hosts in electro-optical devices, as well as solid-state matrices in chemical sensors. An important attribute of xerogels in chemical sensing applications is the porosity of the sol-gel matrix, which results from the formation of the matrix, allows analytes to diffuse into the glass and come in contact with the sensing element. Our main goal, driven in...

  1. Electrode Properties of Dye-Sensitized Solar Cell using Ruthenium Complex/Titania Nano Crystal

    OpenAIRE

    HORIKAWA, Hajime; Ogihara, Takashi; OGATA, Nobuo; ASAHARA, Masahiro; WU, Xing-Zheng

    2006-01-01

    Titania nanocrystals were prepared by hydrolysis of titanium alkoxide in ethanol solution. Thepreparation of titania / alumina thin film was performed on ITO coated glass substrate by dipcoating method using ethanol of titania nanocrystal and boemite sol. The crystal structures,microstructure and thickness of titania / alumina thin film were examined by XRD and SEM. Theadsorption of dye was influenced by the surface structure of thin film. The adsorption of dye on thefilms was improved by the...

  2. 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.

  3. Preparation and Mechanical Performance of Rare Earth-Containing Composite Elastomer

    Institute of Scientific and Technical Information of China (English)

    邱关明; 周兰香; 张明; 中北里志; 井上真一; 冈本弘

    2001-01-01

    Rare earth-containing PSBR sheet was prepared by reaction of rare earth alkoxide with quaternary ammonium salt of pyridine modified SBR (PSBR) latex, and then it was blended with natural rubber (NR) to produce rare earth-containing composite elastomer. It is found that mechanical performance can be improved remarkably. Analyzed by infrared spectrometry (IR), differential scanning calorimetry (DSC) and cross-linking densitometry, the relationship between structure and performance was discussed.

  4. 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.

  5. 1,3,5-trinitroso- and 1,3,5-trinitrohexahydro-1,3,5-triazine-2H6

    International Nuclear Information System (INIS)

    Perdeuteration of 1,3,5-trinitrosohexahydro-1,3,5-triazine was brought about by treatment with potassium alkoxide in CH3O2H(99.5%). The important high energy compound, 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX), was obtained in its perdeuterated modification (>99% 2H) by oxidation of the perdeuterated trinitrosamine with a mixture of nitric acid (100%) and hydrogen peroxide (30%). (author)

  6. Photocatalytic reaction on photofuel cell titania electrode

    OpenAIRE

    Nishikiori, Hiromasa; Kato, Yotaro

    2012-01-01

    Benzoic acid-doped titania electrodes were prepared from titanium alkoxide sols containing benzoic acid in order to examine the photocatalytic reaction of the fuel material concentrated on the titania surface of a photofuel cell electrode. This doping was developed in order to understand the physicochemical processes on the titania rather than to advance the practical use of the photofuel cells. The observed photocurrent and CO(2) and H(2)O productions indicated that the oxidation of the benz...

  7. Study of Silicon Oxycarbide(SiOC) as Anode Materials for Li-ion Batteries

    OpenAIRE

    Vallachira Warriam Sasikumar Pradeep, Pradeep

    2013-01-01

    The principal object of this thesis is the investigation of silicon oxycarbide (SiOC) ceramics as anode material for Li-ion batteries. The investigated materials are prepared by cross linking commercial polymer siloxanes via hydrosylilation reactions or hybrid alkoxide precursors via sol-gel. The cross linked polymer networks are then converted in to ceramic materials by a pyrolysis process in controlled argon atmosphere at 800-1300 °C. In details the influence of carbon content on lithium...

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

    International Nuclear Information System (INIS)

    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, 1H-NMR spectroscopy (if soluble in suitable solvents) and, in some cases, by X-ray fine structure analysis. (orig./EF)

  9. A surface derivatization strategy for combinatorial analysis of cell response to mixtures of protein domains

    OpenAIRE

    Chiang, Chunyi; Karuri, Stella W.; Kshatriya, Pradnya P.; Schwartz, Jeffrey; Schwarzbauer, Jean E.; Karuri, Nancy W.

    2011-01-01

    We report a robust strategy for conjugating mixtures of two or more protein domains to non-fouling polyurethane surfaces. In our strategy, the carbamate groups of polyurethane are reacted with zirconium alkoxide from the vapor phase to give a surface bound oxide that serves as a chemical layer that can be used to bond organics to the polymer substrate. An hydroxyalkylphosphonate monolayer was synthesized on this layer, which was then used to covalently bind primary amine groups in protein dom...

  10. Multidiagnostic Analysis to Track Zeolite Formation

    OpenAIRE

    Castro, M.; Haouas, M.; Taulelle, Francis; Lim, I; Breynaert, Eric; Brabants, Gert; Kirschhock, Christine; Schmidt, W.

    2014-01-01

    Introduction The formation of zeolites in presence of tetraalkylammonium cations from so-called clear solutions using silicon alkoxides is a highly complex process. Our research aims to identify the key mechanisms on a molecular scale with the goal of understanding the factors that drive the formation of zeolites [1]. For this purpose we have used electrospray ionization mass spectrometry (ESI-MS), 29Si and 27Al liquid-NMR spectrometry, DOSY NMR (diffusion experi...

  11. PROCESSING OF SERPENTINITE TAILINGS TO PURE AMORPHOUS SILICA

    OpenAIRE

    Alena Fedorockova; Pavel Raschman; Sucik Gabriel; Plesingerova Beatrice; Popovic Lubos; Briancin Jaroslav

    2015-01-01

    While the published research papers describe preparation of amorphous silica from water glass or using special methods (e.g. hydrolysis of alkoxides), the present study demonstrates a feasible solution for the cheaper synthesis of highly reactive silica using two-stage (acid and alkaline) leaching of serpentinite (Mg3Si2O5(OH)4). The alkaline leaching, the purification of sodium metasilicate solution and the effect of impurities on the precipitation of amorphous silica under the conditions of...

  12. Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization.

    Science.gov (United States)

    Xia, Wei; Salmeia, Khalifah A; Vagin, Sergei I; Rieger, Bernhard

    2015-03-01

    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. PMID:25656829

  13. 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.

  14. A simple sol–gel approach to synthesize nanocrystalline 8 mol% yttria stabilized zirconia from metal-chelate precursors: Microstructural evolution and conductivity studies

    Energy Technology Data Exchange (ETDEWEB)

    Bagchi, Biswajoy; Basu, Rajendra Nath, E-mail: ragenbasu54@gmail.com

    2015-10-25

    A facile non alkoxide based sol–gel technique has been used to synthesize homogeneously distributed nanocrystalline 8 mol% yttria stabilized zirconia (YSZ) powder. The two steps of such powder preparation are gelation and thermal decomposition of metal-chelate complex in aqueous solution. Such nano powder was characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FESEM), Fourier transform infra-red spectroscopy (FTIR) and BET surface area analyser. Upon calcinations at 600 °C, well crystallized nano-sized (10–15 nm) YSZ powder is obtained having spherical morphology and reasonably high surface area. The required ionic conductivity (0.107 S/cm) is achieved with 1200 °C sintered samples when measured at 1000 °C in air. - Graphical abstract: A facile non-alkoxide sol–gel route based on metal-EDTA chelate precursor is provided to synthesize dense nanocrystalline YSZ for use as SOFC electrolyte. - Highlights: • Facile one-step non-alkoxide based sol–gel approach. • Nanocrystalline YSZ synthesis from metal-chelate complex. • High ionic conductivity at low sintering temperature.

  15. Toward compositional design of reticular type porous films by mixing and coating titania-based frameworks with silica

    Directory of Open Access Journals (Sweden)

    T. Kimura

    2015-12-01

    Full Text Available A recently developed reticular type porous structure, which can be fabricated as the film through the soft colloidal block copolymer (e.g., PS-b-PEO templating, is very promising as the porous platform showing high-performance based on its high surface area as well as high diffusivity of targeted organic molecules and effective accommodation of bulky molecules, but the compositional design of oxide frameworks has not been developed so enough to date. Here, I report reliable synthetic methods of the reticular type porous structure toward simple compositional variations. Due to the reproducibility of reticular type porous titania films from titanium alkoxide (e.g., TTIP; titanium tetraisopropoxide, a titania-silica film having similar porous structure was obtained by mixing silicon alkoxide (e.g., tetraethoxysilane and TTIP followed by their pre-hydrolysis, and the mixing ratio of Ti to Si composition was easily reached to 1.0. For further compositional design, a concept of surface coating was widely applicable; the reticular type porous titania surfaces can be coated with other oxides such as silica. Here, a silica coating was successfully achieved by the simple chemical vapor deposition of silicon alkoxide (e.g., tetramethoxysilane without water (with water at the humidity level, which was also utilized for pore filling with silica by the similar process with water.

  16. Toward compositional design of reticular type porous films by mixing and coating titania-based frameworks with silica

    Science.gov (United States)

    Kimura, T.

    2015-12-01

    A recently developed reticular type porous structure, which can be fabricated as the film through the soft colloidal block copolymer (e.g., PS-b-PEO) templating, is very promising as the porous platform showing high-performance based on its high surface area as well as high diffusivity of targeted organic molecules and effective accommodation of bulky molecules, but the compositional design of oxide frameworks has not been developed so enough to date. Here, I report reliable synthetic methods of the reticular type porous structure toward simple compositional variations. Due to the reproducibility of reticular type porous titania films from titanium alkoxide (e.g., TTIP; titanium tetraisopropoxide), a titania-silica film having similar porous structure was obtained by mixing silicon alkoxide (e.g., tetraethoxysilane) and TTIP followed by their pre-hydrolysis, and the mixing ratio of Ti to Si composition was easily reached to 1.0. For further compositional design, a concept of surface coating was widely applicable; the reticular type porous titania surfaces can be coated with other oxides such as silica. Here, a silica coating was successfully achieved by the simple chemical vapor deposition of silicon alkoxide (e.g., tetramethoxysilane) without water (with water at the humidity level), which was also utilized for pore filling with silica by the similar process with water.

  17. FACTORS INFLUENCING THE PREPARATION OF TiO2 NANOPOWDERS FROM TITANIA SOL

    Directory of Open Access Journals (Sweden)

    F. MASTALI KHAN TEHRANI

    2011-03-01

    Full Text Available Titania nanoparticles with high photocatalytic activity were prepared from titanium alkoxide dissolved in alcohol and water under acidic conditions. The effects of the key parameters including (alkoxide/water ratio, (alkoxide/alcohol ratio, precursor type, solvent type, type and concentration of stabilizer, calcination temperature, presence of methylcellulose (MC and hydrothermal treatment were studied. The optimal conditions were obtained through an experimental design technique. This technique is also used to find the main factors influencing the degradation of methylene blue (MB and mass percent of anatase phase. The powders characteristics were investigated by XRD and Brunauer-Emmett-Teller (BET methods. The X-ray diffraction studies showed that the product has anatase crystal structure with average particle size below 13 nm. The photocatalytic activities of the TiO2 nanoparticles were assessed by the degradation of MB in aqueous solution. According to the obtained results, the kinetics of photocatalytic reaction followed pseudo-first-order model. The results showed that the main factors influencing the degradation of MB were the type of stabilizer, presence of MC, hydrothermal treatment, solvent type and calcination temperature. Specific surface areas of the nanoparticles were between 76-198 m2/g.

  18. Ti(IV) and Zr(IV) alkoxy complexes with O-donor ligands. Synthesis, structural characterization and applications

    International Nuclear Information System (INIS)

    Extensive studies of complexes of titanium(IV) and zirconium(IV) alkoxides with O-donor ligands observed for the last few years are a result of their wide applications in nanomaterial technologies. Various physicochemical properties of TiO2 and ZrO2 including high reference factor (n = 2.616-2.903 TiO2), low absorption in visible range, photoluminescence, high dielectric constant (αTiO2 = 120 for rutile), high stability and chemical resistance have significant influence on their use. Thin metal oxide layers are prepared by vaporization and condensation methods, hydrolysis in the flame, vacuum deposition, sol-gel techniques, and also chemical vapor deposition (CVD). The last two methods are most often used to prepare high quality ceramic materials, thin metal oxide layers, organic-inorganic hybrid polymers, doped materials (M2O/M'; M = Ti, Zr; M' = Cu, Ag, Au, Pt, Pd) as well as mesoporous materials. In both techniques a very important role is played by precursors, which influence CVD process, and the structure of deposited layers. Ti(IV) and Zr(IV) alkoxides (M(OR)4) are usually used as CVD precursors of thin TiO2 and ZrO2 layers. However, high reactivity of M(OR)4 towards nucleophilic reagents, in particularly hydrolysis and condensation of metal alkoxides, lead to precipitation of oxo-polymers. In order to stabilize the alkoxy precursor, Ti(IV) and Zr(IV) complexes containing anionic bidentate groups, such as β-diketones, carboxylates, alkylamides, sulfonates have been studied. In the presented paper, the review of synthetic methods and structural characterization of the following type of complexes [M(OR)x(L)x] (M Ti(IV), Zr(IV), OR = alkoxy ligand, L β-diketones, carboxylates) has been carried out. The volatile properties of these compounds as well as their low reactivity towards water caused that above mentioned complexes are used as TiO2 and ZrO2 precursors in CVD processes and therefore a special attention has been paid to this problem. Substitution of

  19. 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).

  20. 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

    OpenAIRE

    Antonio A. S. Alfaya; Kubota, Lauro T.

    2002-01-01

    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 prepar...

  1. Introduction of bridging and pendant organic groups into mesoporous alumina materials.

    Science.gov (United States)

    Grant, Stacy M; Woods, Stephan M; Gericke, Arne; Jaroniec, Mietek

    2011-11-01

    Incorporation of organic functionalities into soft-templated mesoporous alumina was performed via organosilane-assisted evaporation induced self-assembly using aluminum alkoxide precursors and block copolymer templates. This strategy permits one to obtain mesoporous alumina-based materials with tailorable adsorption, surface and structural properties. Isocyanurate, ethane, mercaptopropyl, and ureidopropyl-functionalized mesoporous alumina materials were synthesized with relatively high surface area and large pore volume with uniform and wormhole-like mesopores. The presence of organosilyl groups within these hybrid materials was confirmed by IR or Raman spectroscopy and their concentration was determined by elemental analysis. PMID:21988174

  2. Preparation and characterization of VOx/TiO2 catalytic coatings on stainless steel plates for structured catalytic reactors.

    OpenAIRE

    Giornelli, Thierry; Löfberg, Axel; Bordes-Richard, Elisabeth

    2006-01-01

    1 The parameters to be controlled to coat metallic walls by VOx/TiO2 catalysts which are used in the mild oxidation of hydrocarbons and NOx abatement are studied. Stainless steel (316 L) was chosen because of its large application in industrial catalytic reactors. TiO2 films on stainless steel were obtained by dip-coating in two steps. Superficially oxidized plates were first dipped in Ti-alkoxide sol-gel to be coated by a very thin layer of TiO2. On this anchoring layer was then deposited a ...

  3. 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.

  4. Preparation of self-sustained film by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    曹冰; 朱从善

    1999-01-01

    Large size self-sustained film with considerable thickness ranging from 30 to 500 μm was prepared with sol-gel method by using dimethyldiethoxysilane/tetraethoxysilane composite alkoxide as precursor. The film exhibits good plasticity as well. Various factors that may influence the film properties were investigated. IR and AFM techniques were adopted to study the film structure and surface morphology. Gas chromatogram/mass spectrum technique was also adopted to characterize the network structure of the material through identification of different polymers formed during hydrolysis and condensation course.

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

    OpenAIRE

    C.O. Avellaneda; Aegerter, M.A.; A. Pawlicka

    1998-01-01

    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 variati...

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

    International Nuclear Information System (INIS)

    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.

  7. Preparation of 4-amino-2,4-dioxobutanoic acid

    Energy Technology Data Exchange (ETDEWEB)

    Unkefer, Pat J.; Martinez, Rodolfo A.; Glass, David R.

    2016-03-22

    A process for synthesizing 4-amino-2,4-dioxobutanoic acid involves reacting diethyl oxalate with an alkoxide in ethanol to form a reaction mixture, and afterward adding ethyl cyanoacetate to the reaction mixture and allowing a reaction to proceed under conditions suitable to form a first reaction product of the formula diethyl 2-cyano-3-hydroxy-butenedioate, and then isolating the diethyl 2-cyano-3-hydroxy-butenedioate, and afterward reacting the diethyl-2-cyano-3-hydroxy-butenedioate with an aqueous hydroxide under conditions suitable to form 4-amino-2,4-dioxobutanoic acid.

  8. Bonding mechanism and performance of ceramic coatings by sol-gel process

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Thin alumina coatings were prepared on carbide tools to enhance their wear-resistant ability by dip coating from an aluminum alkoxide solution. The coating eventually obtained was perfectly integrated, without any macroscopic defect, and showed good performance in turning medium carbon steel, which presented a novel and promising coating method for cutting tools. The coating morphology before and after heat treatment was examined with the aid of a scanning electron microscope (SEM). The composition of coating and interface layer as well as the crystal structure of coating was characterized by X-ray diffraction (XRD). The elemental distribution near the interlayer was analyzed by electron probe microanalysis (EPMA).

  9. Preparation of hydrophobic coatings

    Science.gov (United States)

    Branson, Eric D.; Shah, Pratik B.; Singh, Seema; Brinker, C. Jeffrey

    2009-02-03

    A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150.degree.. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.

  10. 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.

  11. Ni-based heterogeneous catalyst from a designed molecular precursor for the efficient electrochemical water oxidation.

    Science.gov (United States)

    Kuznetsov, Denis A; Konev, Dmitry V; Komarova, Natal'ya S; Ionov, Andrey M; Mozhchil, Rais N; Fedyanin, Ivan V

    2016-07-28

    Bimetallic Ni-Mo alkoxide was synthesized and exploited as the single-source precursor for the solution-processed deposition of the mixed-oxide layers on different conducting surfaces. Upon potential cycling in 1 M NaOH, these composites convert, in situ, into highly porous NiOx/NiOOH catalysts characterized by the high electrocatalytic activity for water oxidation under both basic (pH 13.6) and near neutral (pH 9.2) conditions. PMID:27354324

  12. Thermal Oxidation Resistance of Rare Earth-Containing Composite Elastomer

    Institute of Scientific and Technical Information of China (English)

    邱关明; 张明; 周兰香; 中北里志; 井上真一; 冈本弘

    2001-01-01

    The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.

  13. 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. PMID:25826714

  14. 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...

  15. Photocatalytic degradation of PCP-Na with TiO2 photocatalysis loaded with platinum

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Titanium dioxide(TiO2 ) samples of different crystal forms were prepared by hydrolysis tetrabutyl titanate in various water to alkoxide ratios and sintering the hydrolysis product at different temperatures.The photocatalysts coated on hollow glass beads and loaded with platinum varying from 0.2% to 2.4% by weight.The photecatalytic degradation rate of sodium pentachlorophenolate (PCP- Na) depends on the preparing conditions such as.:sintering temperatures,water to alkoxide ratios(R),platinum content and the size.The proper conditions of preparation photoeatalysts are as follows:the ratio of TiO2:sodium silicate :hollow glass beads :platinum is 10:5:20:0.15(w/w),R is 100,sintering temperature is 650℃,and the size of hollow glass is 0.5 - 1 mm.Under these conditions,the ratio between aeatase and rutile of the photocatalyst is 2:1,and the photocatalytie activity is high.

  16. Characterization of fine grain Ba0.995Y0.005TiO3 ceramics obtained from gel-precursor nanopowder.

    Science.gov (United States)

    Cernea, Marin; Monnereau, Odile; Llewellyn, Philip; Vasile, Eugeniu

    2007-03-01

    Using an acetate-alkoxide sol-gel route in which the precursors are barium acetate, yttrium isopropoxide and titanium diisopropoxide bis-acetylacetonate, we prepared a ferroelectric material with the formula: Ba1-xYxTiO3, x = 0.005. SEM analysis showed a polymeric microstructure of the gel due to the chelated titanium alkoxide precursor used as starting materials. The evolution of the structure and microstructure of the precursor gel heated at temperatures up to 1000 degrees C was studied by various techniques. The powder obtained by heating the gel at 1100 degrees C presented a homogeneous structure consisting of submicronic particles (approximately 200 nm). XRD and SAED analyses revealed that Ba0.995Y0.005TiO3 nanocrystals of about 5-10 nm appeared at 600 degrees C, together with BaCO3. The presence of barium carbonate was identified also by IR spectroscopy and thermal analyses. The ceramics obtained from the as-prepared powder presented good dielectric properties (capacitance = 840 pF/dielectric constant = 3860 and dielectric loss (tandelta) = 0.078 at Curie temperatures of 120-121 degrees C). PMID:17450868

  17. Effect of Change in Ba Concentration on Crystallintiy and Dielectric Constant of the Sol-Gel Deposited Barium Strontium Titante (BST Films on n-Type Si Wafer

    Directory of Open Access Journals (Sweden)

    C.C. Tripathi

    2011-01-01

    Full Text Available Thin (Bax, Sr1 – xTiO3 (BST films of different chemical compositions (x = 0.3 0.5 & 0.7 were prepared by the sol-gel process using barium acetate, strontium acetate and titanium isopropoxide as metal alkoxides. The titanium isopropoxide was dissolved in acetyl acetone (chelating agent and mixing the resultant solution with barium and strontium acetate dissolved in acetic acid solution. The alkoxide group in titanium isopropoxide was replaced by acetate ligand and after hydrolysis and condensation process a complex solution was obtained. This solution was deposited on n-type (111 Si wafers by spin coating and after drying at 350 ºC the samples were annealed at 700 ºC in oxygen ambient. The precise control of composition of different species is important for producing good quality films having high crystallinity and dielectric constant. The crystallinity of the film was found to increase with the increase of Ba concentration as found from X-ray diffraction. The calculated value of dielectric constant from CV measurements revealed that the film of (Ba0.7, Sr0.3 TiO3 had the maximum dielectric constant as 463 and the surface was examined by SEM.

  18. Crystallinity and stoichiometry of nano-structured sol-gel-derived BaTiO{sub 3} monolithic gels

    Energy Technology Data Exchange (ETDEWEB)

    Shimooka, Hirokazu [Kyushu Inst. of Tech., Kitakyushu, Fukuoka (Japan). Dept. of Applied Chemistry; Kuwabara, Makoto [Univ. of Tokyo (Japan). Dept. of Materials Science

    1996-11-01

    The crystallization behavior and stoichiometric changes of barium titanium alkoxide-derived monolithic gels prepared by the sol-gel process using a high-concentration Ba,Ti precursor solution (0.8 mol/L) were investigated during aging at room temperature. Crystallization of the gels (which were amorphous, per X-ray diffraction analysis immediately after gelation) into the BaTiO{sub 3} perovskite phase increased during aging and was associated with significant shrinkage of the gels. Crystallization reached a value of {approximately}82% by the final stage of shrinkage, assuming the degree of crystallization of a gel treated at 600 C to be 100%. The stoichiometry of the gels (Ba/Ti molar ratio) also changed considerably during aging, as estimated by the concentrations of Ba and Ti that remained in the expelled liquid resulting from syneresis at any time during the aging process. Deviation in the Ba/Ti ratio of the precursor solution ranged from 0.015 at the initial stage of shrinkage to 0.003 at the final stage, a value determined by inductively coupled plasma atomic emission spectroscopy. The present study demonstrates the great advantage of using high-concentration precursor solutions of barium titanium alkoxides, rather than low-concentration solutions, to obtain BaTiO{sub 3} gel monoliths with high density and crystallinity and little stoichiometric deviation, by sol-gel processing at room temperature.

  19. Rational design, synthesis and 2D-QSAR study of novel vasorelaxant active benzofuran-pyridine hybrids.

    Science.gov (United States)

    Srour, Aladdin M; Abd El-Karim, Somaia S; Saleh, Dalia O; El-Eraky, Wafaa I; Nofal, Zeinab M

    2016-05-15

    Reaction of 3-aryl-1-(benzofuran-2-yl)-2-propen-1-ones 3a-c with malononitrile in the presence of sufficient amount of sodium alkoxide in the corresponding alcohol proceeds in a regioselective manner to afford 2-alkoxy-4-aryl-6-(benzofuran-2-yl)-3-pyridinecarbonitriles 4-37, which also obtained by treating ylidenemalononitriles 6a-q with 2-acetylbenzofuran 1 in the presence of sufficient amount of sodium alkoxide in the corresponding alcohol. The new chemical entities showed significant vasodilation properties using isolated thoracic aortic rings of rats pre-contracted with norepinephrine hydrochloride standard technique. Compounds 11, 16, 21, 24 and 30 exhibited remarkable activity compared with amiodarone hydrochloride the reference standard used in the present study. CODESSA-Pro software was employing to obtain a statistically significant QSAR model describing the bioactivity of the newly synthesized analogs (N=31, n=5, R(2)=0.846, R(2)cvOO=0.765, R(2)cvMO=0.778, F=27.540. s(2)=0.002). PMID:27048942

  20. Liquid-Phase Synthesis of Ba2V2O7 Phosphor Powders and Films Using Immiscible Biphasic Organic-Aqueous Systems.

    Science.gov (United States)

    Takahashi, Mami; Hagiwara, Manabu; Fujihara, Shinobu

    2016-08-15

    A liquid-phase synthesis of inorganic phosphor materials at a moderate temperature was proposed by using immiscible liquid-liquid biphasic systems. A self-activated Ba2V2O7 phosphor was actually synthesized from vanadium alkoxide dissolved in an organic solution and barium acetate in an aqueous solution. A mild hydrolysis reaction of the alkoxide started at the organic-inorganic interface, and an intermediate compound, Ba(VO3)2·H2O, was initially formed. Ba2V2O7 powders were then obtained by the conversion from Ba(VO3)2·H2O promoted in the aqueous solution. Ba2V2O7 films were obtained on surface-modified silica glass substrates through the similar chemical reactions. Factors such as the surface state of substrates, the kind of organic solvents, and the volume of aqueous solutions were examined to improve the film deposition behavior. The resultant Ba2V2O7 materials showed broad-band visible photoluminescence upon irradiation with ultraviolet light based on the charge transfer transition in the VO4(3-) units existing as dimers. PMID:27472450

  1. Titanium-based polymeric electrospun nanofiber mats as a novel organic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Barakat, Nasser A.M., E-mail: nasser@jbnu.ac.kr [Organic Materials and Fiber Engineering Department, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Chemical Engineering Department, Faculty of Engineering, El-Minia University, El-Minia (Egypt); Hamza, A.M. [Department of Physics, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Al-Deyab, Salem S. [Petrochemical Research Chair, Department of Chemistry, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia); Qurashi, Ahsanulhaq [Center of Excellence in Nanotechnology and Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Kim, Hak Yong, E-mail: khy@jbnu.ac.kr [Organic Materials and Fiber Engineering Department, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2012-01-25

    Highlights: Black-Right-Pointing-Pointer Ti-based electrospun nanofibers are introduced as a novel organic semiconductor. Black-Right-Pointing-Pointer Layer from the proposed nanofibers supported on silicon substrate behaves as diode. Black-Right-Pointing-Pointer The study opens an avenue to utilize alkoxides/polymer nanofibers as semiconductor. - Abstract: Organic semiconductors have been extensively used in the electronic devices as activate components. However, most of the introduced organic materials are structurally complicated which leads to high commercial production cost. In this study, thin layer from titanium isopropoxide/poly(vinyl acetate) electrospun nanofibers is introduced as a new class of semiconducting materials. Electrospinning as a simple, effective, high yield and low cost process was used to prepare the introduced nanofiber films. The obtained results indicated that the titanium isopropoxide content has a distinct influence on the electrical conductivity as increasing the content shifts the conduction mechanism toward the semiconducting behavior. At 40 and 50 wt% titanium isopropoxide, the nanofiber mats behave as a semiconductor. Within the ohmic region in the IV chart, the saturation current and the corresponding applied voltage are directly proportional to the titanium isopropoxide content. Leakage current study indicated that Schottky emission is the dominant mechanism through both of the negative and positive bias regions. The introduced titanium isopropoxide/poly (vinyl acetate) nanofiber mats might open a new avenue to utilize the metal alkoxide/polymer nanofibers as novel and effective type of semiconducting materials.

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

    Energy Technology Data Exchange (ETDEWEB)

    Umalas, Madis [Institute of Physics, University of Tartu, Riia 142, 51014, Tartu (Estonia); Estonian Nanotechnology Competence Centre, Riia 142, 51014, Tartu (Estonia); Hussainova, Irina, E-mail: irina.hussainova@ttu.ee [Department of Materials Engineering, Tallinn University of Technology, Ehitajate 5, 19086, Tallinn (Estonia); ITMO University, Kronverksky 49, St. Petersburg, 197101 (Russian Federation); Reedo, Valter [Institute of Physics, University of Tartu, Riia 142, 51014, Tartu (Estonia); Young, Der-Liang [Department of Materials Engineering, Tallinn University of Technology, Ehitajate 5, 19086, Tallinn (Estonia); Cura, Erkin; Hannula, Simo-Pekka [Department of Materials Science and Engineering, Aalto University, School of Chemical Technology, POB 16200, Aalto, 00076 (Finland); Lõhmus, Rünno [Institute of Physics, University of Tartu, Riia 142, 51014, Tartu (Estonia); Estonian Nanotechnology Competence Centre, Riia 142, 51014, Tartu (Estonia); Lõhmus, Ants [Institute of Physics, University of Tartu, Riia 142, 51014, Tartu (Estonia)

    2015-03-01

    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{sub 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{sub 2} solid solution by spark plasma sintering. • Sintered ZrTiC{sub 2} have good mechanical properties.

  3. 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.

  4. 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.

  5. Water vapor-controlled thermal plasma chemical vapor deposition of double-layered TiN/PSZ coatings on Si and WC-Co substrates

    International Nuclear Information System (INIS)

    Double-layer TiN/PSZ film coatings were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by thermal plasma chemical vapor deposition (CVD) containing water vapor. The partially stabilized zirconia (PSZ) layer was coated on a TiN film by oxidation of Zr- and Y-alkoxides with H2O supplied by both constant and step-wise methods. Double-layer TiN/PSZ coatings deposited on Si wafers and WC-Co by the two H2O supply methods were approximately 2 μm thick. TEM observation showed that the interface between the TiN and PSZ in the double-layer TiN/PSZ formed by the step-wise H2O supply is more adhesive than under constant H2O supply. Double-layer TiN/PSZ films coated on WC-Co substrates by the step-wise supply exhibited good crater wear resistance, comparable to a commercial double-layer TiN/Al2O3 coating by thermal CVD.

  6. Water vapor-controlled thermal plasma chemical vapor deposition of double-layered TiN/PSZ coatings on Si and WC-Co substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Takanori [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Shimada, Shiro, E-mail: shimashi@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Kiyono, Hajime [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Tsujino, Jiro [Research and Development Department, Hokkaido Electric Power Co. Ltd., 2-1, Tsuishikari, Ebetsu City 067-0033 (Japan); Yamazaki, Isao [Hokkaido Sumiden Precision Industries Ltd., 776 Naie, Sorachi-gun, Hokkaido 079-0304 (Japan)

    2010-08-25

    Double-layer TiN/PSZ film coatings were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by thermal plasma chemical vapor deposition (CVD) containing water vapor. The partially stabilized zirconia (PSZ) layer was coated on a TiN film by oxidation of Zr- and Y-alkoxides with H{sub 2}O supplied by both constant and step-wise methods. Double-layer TiN/PSZ coatings deposited on Si wafers and WC-Co by the two H{sub 2}O supply methods were approximately 2 {mu}m thick. TEM observation showed that the interface between the TiN and PSZ in the double-layer TiN/PSZ formed by the step-wise H{sub 2}O supply is more adhesive than under constant H{sub 2}O supply. Double-layer TiN/PSZ films coated on WC-Co substrates by the step-wise supply exhibited good crater wear resistance, comparable to a commercial double-layer TiN/Al{sub 2}O{sub 3} coating by thermal CVD.

  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

    Drop on demand deposition (DoD) of titanium oxide thin films (<500 nm) is performed via a novel titanium-alkoxide-based solution that is tailored as a reactive ink for inkjet printing. The ink is developed as water-based solution by a combined use of titanium isopropoxide and n-methyldiethanolami......Drop on demand deposition (DoD) of titanium oxide thin films (reactive ink for inkjet printing. The ink is developed as water-based solution by a combined use of titanium isopropoxide and n......-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...... of MDEA is here elucidated in terms of long term stability. The ink printability parameter (Z) is optimized, resulting in a reactive solution with printability, Z, >1, and chemical stability up to 600 h. Thin titanium oxide films (

  8. 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)

    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)

  9. Liquid-Phase Synthesis of Ba2V2O7 Phosphor Powders and Films Using Immiscible Biphasic Organic-Aqueous Systems.

    Science.gov (United States)

    Takahashi, Mami; Hagiwara, Manabu; Fujihara, Shinobu

    2016-08-15

    A liquid-phase synthesis of inorganic phosphor materials at a moderate temperature was proposed by using immiscible liquid-liquid biphasic systems. A self-activated Ba2V2O7 phosphor was actually synthesized from vanadium alkoxide dissolved in an organic solution and barium acetate in an aqueous solution. A mild hydrolysis reaction of the alkoxide started at the organic-inorganic interface, and an intermediate compound, Ba(VO3)2·H2O, was initially formed. Ba2V2O7 powders were then obtained by the conversion from Ba(VO3)2·H2O promoted in the aqueous solution. Ba2V2O7 films were obtained on surface-modified silica glass substrates through the similar chemical reactions. Factors such as the surface state of substrates, the kind of organic solvents, and the volume of aqueous solutions were examined to improve the film deposition behavior. The resultant Ba2V2O7 materials showed broad-band visible photoluminescence upon irradiation with ultraviolet light based on the charge transfer transition in the VO4(3-) units existing as dimers.

  10. Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films

    Science.gov (United States)

    Glynn, Colm; Creedon, Donal; Geaney, Hugh; Armstrong, Eileen; Collins, Timothy; Morris, Michael A.; Dwyer, Colm O’

    2015-01-01

    Solution processed metal oxide thin films are important for modern optoelectronic devices ranging from thin film transistors to photovoltaics and for functional optical coatings. Solution processed techniques such as dip-coating, allow thin films to be rapidly deposited over a large range of surfaces including curved, flexible or plastic substrates without extensive processing of comparative vapour or physical deposition methods. To increase the effectiveness and versatility of dip-coated thin films, alterations to commonly used precursors can be made that facilitate controlled thin film deposition. The effects of polymer assisted deposition and changes in solvent-alkoxide dilution on the morphology, structure, optoelectronic properties and crystallinity of vanadium pentoxide thin films was studied using a dip-coating method using a substrate withdrawal speed within the fast-rate draining regime. The formation of sub-100 nm thin films could be achieved rapidly from dilute alkoxide based precursor solutions with high optical transmission in the visible, linked to the phase and film structure. The effects of the polymer addition was shown to change the crystallized vanadium pentoxide thin films from a granular surface structure to a polycrystalline structure composed of a high density of smaller in-plane grains, resulting in a uniform surface morphology with lower thickness and roughness. PMID:26123117

  11. 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. PMID:26726529

  12. Identification of Ti clusters during nucleation and growth of sol-gel-derived TiO2 nanoparticles.

    Science.gov (United States)

    Simonsen, Morten Enggrob; Søgaard, Erik Gydesen

    2013-01-01

    In the present work, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the titanium clusters present during nucleation and growth of sol-gel derived TiO2 nanoparticles. Depending on the alkoxide precursor used, Ti clusters of different sizes were identified [titanium isopropoxide (TTIP)-11-12 Ti atoms, titanium butoxide (TTB)-10-11 Ti atoms and titanium tetraethoxide (TTE)-5-7 Ti atoms]. The Ti-O-Ti backbone/core of the titanium clusters were found to be quite stable after formation and do not easily break up into smaller clusters. The results of this investigation suggest that these clusters are used as building blocks in the growth during the induction period. The h-ratio (n H2O/n alcoxide) and the pH were not found to influence the identity of the Ti clusters present during nucleation of the growth of sol-gel derived TiO2 nano-particles, although the induction period was greatly influenced. The reactivity of the alkoxy group are OEt > OPri > OBu. The difference in reactivity of the alkoxides is generally believed to be due to the increasing size of the alkoxy group which causes sterical hindrance during the nucleophilic substitution reaction. PMID:24575625

  13. 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.

  14. Rational design, synthesis and 2D-QSAR study of novel vasorelaxant active benzofuran-pyridine hybrids.

    Science.gov (United States)

    Srour, Aladdin M; Abd El-Karim, Somaia S; Saleh, Dalia O; El-Eraky, Wafaa I; Nofal, Zeinab M

    2016-05-15

    Reaction of 3-aryl-1-(benzofuran-2-yl)-2-propen-1-ones 3a-c with malononitrile in the presence of sufficient amount of sodium alkoxide in the corresponding alcohol proceeds in a regioselective manner to afford 2-alkoxy-4-aryl-6-(benzofuran-2-yl)-3-pyridinecarbonitriles 4-37, which also obtained by treating ylidenemalononitriles 6a-q with 2-acetylbenzofuran 1 in the presence of sufficient amount of sodium alkoxide in the corresponding alcohol. The new chemical entities showed significant vasodilation properties using isolated thoracic aortic rings of rats pre-contracted with norepinephrine hydrochloride standard technique. Compounds 11, 16, 21, 24 and 30 exhibited remarkable activity compared with amiodarone hydrochloride the reference standard used in the present study. CODESSA-Pro software was employing to obtain a statistically significant QSAR model describing the bioactivity of the newly synthesized analogs (N=31, n=5, R(2)=0.846, R(2)cvOO=0.765, R(2)cvMO=0.778, F=27.540. s(2)=0.002).

  15. Electrostatic spray deposition of nanoporous CoO/Co composite thin films as anode materials for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Sun Yi; Du Chun; Feng Xuyong; Yu Yan [CAS Key Laboratory of Materials for Energy Conversions, Department of Materials Science and Engineering, University of Science and Technology of China, Anhui, Hefei 230026 (China); Lieberwirth, Ingo [Max Planck Institute for Polymer Research, Mainz 55128 (Germany); Chen Chunhua, E-mail: cchchen@ustc.edu.cn [CAS Key Laboratory of Materials for Energy Conversions, Department of Materials Science and Engineering, University of Science and Technology of China, Anhui, Hefei 230026 (China)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer The films are made of in situ produced hollow spheres consisting of conductive Co and electrochemically active CoO. Black-Right-Pointing-Pointer The homogeneous distribution of Co revealed by EELS in the film is important for the good rate capability. Black-Right-Pointing-Pointer The CoO/Co composite films exhibit excellent rate performance with 69.5% of capacity retention at 10C. - Abstract: Cobalt alkoxide suspension is obtained by heating a mixed polyalcohol solution of cobalt acetate in an oil bath at 170 Degree-Sign C. Thermogravimetric analysis is adopted to determine the chemical formula of the alkoxide powder in the suspension. With the suspension precursors, CoO/Co composite thin films are fabricated by electrostatic spray deposition and subsequent heat treatment in nitrogen. They are characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Electron energy loss spectroscopy mapping is applied to determine the lateral two-dimensional chemical distribution of metallic Co in the nanocomposites. The thin film can deliver a high reversible capacity of 1182.1 mAh g{sup -1} at 70th cycle and retain 69.5% of the initial capacity at 10C. The in situ production of metallic cobalt and the unique hollow structure of the particles can account for the good electrochemical performance.

  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. Novel routes to metalloorganics containing aluminum from minerals

    Science.gov (United States)

    Narayanan, Ramasubramanian

    Novel pathways for synthesizing Al metalloorganics directly from widely available oxides and oxo-hydroxides of aluminum are developed. The Al metalloorganics are then used to produce low-cost precursors for ceramics and polymers containing Al. Alumatrane, an unique, air-stable, aluminum alkoxide is prepared in one step from aluminum hydroxide in quantitative yields. Subsequently, alumatrane was used to prepare and characterize all group II dialuminate ceramics (MAlsb2Osb4, M = Mg, Ca, Sr, Ba). Similarly, an air-stable alkoxide of silicon was synthesized directly from SiOsb2, and is used in conjunction with alumatrane to produce precursors for aluminosilicate ceramics (MAlSiOsb4, M = K, Li, Na). Aluminum formate is synthesized, in differing efficiencies, from different crystalline minerals of Al, by direct dissolution in formic acid. A few other aluminum carboxylates are also synthesized, either directly from minerals or from aluminum formates, thus expanding the scope of the acid dissolution of aluminum hydroxides. Aluminum allyloxypropanoate (AAP) (Al(Osb2CCHsb2CHsb2OCH{=}CHsb2)sb2(OH)), an aluminum carboxylate with a polymerizable group has been synthesized from aluminum formate. This, has been incorporated into methyl methacrylate (MMA) polymers to impart fire retardancy. The increase in char yields as a result of AAP incorporation, indicate improved fire retardancy. Fire retardant characteristics of alumatrane has also been investigated, in MMA polymers and in a polyurethane polymer, taking char yields as a measure of fire retardance efficiency.

  18. 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.

  19. Synthesis and functionalization of magnetite nanoparticles with different amino-functional alkoxysilanes

    Energy Technology Data Exchange (ETDEWEB)

    Bini, Rafael A., E-mail: r_bini11@yahoo.com.br [Institute of Chemistry, Laboratory of Magnetic Materials and Colloids, Sao Paulo State University-UNESP, Caixa Postal 355, Araraquara 14800-900 (Brazil); Marques, Rodrigo Fernando C. [Institute of Science and Technology, Alfenas Federal University, Pocos de Caldas 37701-100 (Brazil); Santos, Francisco J. [Institute of Chemistry, Laboratory of Magnetic Materials and Colloids, Sao Paulo State University-UNESP, Caixa Postal 355, Araraquara 14800-900 (Brazil); Chaker, Juliano A. [FCE, Brasilia University, Caixa Postal 7380, Brasilia 72220-140 (Brazil); Jafelicci, Miguel [Institute of Chemistry, Laboratory of Magnetic Materials and Colloids, Sao Paulo State University-UNESP, Caixa Postal 355, Araraquara 14800-900 (Brazil)

    2012-02-15

    Superparamagnetic iron oxide (SPIO) nanoparticles show great promise for many biotechnological applications. This paper addresses the synthesis and characterization of SPIO nanoparticles grafted with three different alkoxysilanes: 3-aminopropyl-triethoxysilane (APTES), 3-aminopropyl-ethyl-diethoxysilane (APDES) and 3-aminopropyl-diethy-ethoxysilane (APES). SPIO nanoparticles with an average particle diameter of 10 nm were prepared by chemical sonoprecipitation. As confirmed by Fourier transform infrared (FTIR) spectroscopy, silylation of these nanoparticles occurs through a two-step process. Decreasing the number of alkoxide groups reduced the concentration of free amino groups on the SPIO surface ([SPIO-NH{sub 2}]-APTES>APDES>APES). This phenomenon results from steric contributions and the formation of H-bonded amines provided by the ethyl groups present in the APDES and APES molecules. A simulation of SPIO nanoparticles in a saline physiologic solution shows that the ethyl groups impart larger steric stability onto the ferrofluids, which reduces aggregation. The magnetization (M) versus magnetic field (H) curves show that the synthesized iron oxide nanoparticles display superparamagnetic behavior. The zero-field cooling (ZFC) and field cooling (FC) curves show that the changes in the blocking temperature depend on the alkoxysilane-functionalized particle surface. - Highlights: > Superparamagnetic iron oxide nanoparticles were grafted with different alkoxysilanes. > The decrease of alkoxide group number reduced the concentration of free amino group. > We correlate the influence of the amino and ethyl groups with their colloidal property. > Inter-particles aggregation analyzed by magnetic measurement.

  20. Carbocation Stability in H-ZSM5 at High Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, Glen A. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Cheng, Lei [Argonne National Lab. (ANL), Argonne, IL (United States); Bu, Lintao [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kim, Seonah [National Renewable Energy Lab. (NREL), Golden, CO (United States); Robichaud, David J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Nimlos, Mark R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Curtiss, Larry A. [Argonne National Lab. (ANL), Argonne, IL (United States); Beckham, Gregg T. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-26

    Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e., an alkoxide). To determine if carbocations can exist at high temperatures in zeolites, where these catalysts are finding new applications for biomass vapor-phase upgrading (~500 °C), the stability of carbocations and the corresponding alkoxides were calculated with two ONIOM embedding methods (M06-2X/6-311G(d,p):M06-2X/3-21G) and (PBE-D3/6-311G(d,p):PBE-D3/3-21G) and plane-wave density functional theory (DFT) using the PBE functional corrected with entropic and Tkatchenko–Scheffler van der Waals corrections. Additionally, the embedding methods tested are unreliable at finding minima for primary carbocations, and only secondary or higher carbocations can be described with embedding methods consistent with the periodic DFT results. The relative energy between the carbocations and alkoxides differs significantly between the embedding and the periodic DFT methods. The difference is between ~0.23 and 14.30 kcal/mol depending on the molecule, the model, and the functional chosen for the embedding method. At high temperatures, the pw-DFT calculations predict that the allyl, isopropyl, and sec-butyl cations exhibit negligible populations while acetyl and tert-butyl cations exhibit significant populations (>10%). Furthermore, the periodic DFT results indicate that mechanisms including secondary and tertiary carbocations intermediates or carbocations stabilized by adjacent oxygen or double bonds are

  1. Optical and morphological properties of sol gel derived titanium dioxide films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, A. B. [Department of Physics, Nabira Mahavidyalaya, Katol-441302 (India); Sharma, S. K. [Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore-560012 (India); M, Vishwas [Department of Physics, Govt. Science College, Bangalore-560067 (India); Rao, K. Narasimha [Department of Instrumentation, Indian Institute of Science, Bangalore-560012 (India)

    2015-08-28

    Titanium oxide (Titania) thin films were synthesized on different substrates via the sol-gel dip-coating method using alkoxide solution. Some selected samples were also prepared with different percentage of Lead (Pb). The influence of Pb addition in precursor sol on the optical properties of titanium dioxide thin films was studied. The optical transmittance in the visible region has increased with increase in weight percentage of lead. The refractive index was slightly decreased with Pb addition. Crystallization of these coatings was achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by Scanning Electron Microscopy. Increase in average grain size from 250 nm to 350 nm with increase in Pb concentration is observed. Films were appeared to more coarse with increase in Pb addition. An increase in Pb addition resulted increase in average roughness from 12 nm to 25 nm.

  2. Catalytic Radical Reduction in Aqueous Solution by a Ruthenium Hydride Intermediate.

    Science.gov (United States)

    Htet, Yamin; Tennyson, Andrew G

    2016-07-18

    Some manganese complexes can catalyze both antioxidant and pro-oxidant reactions, whereby the disparate reactivity modes are determined by the catalyst environment and afford distinct therapeutic effects. We recently reported the reduction of radicals in buffered aqueous solution catalyzed by a ruthenium complex with biologically relevant non-tertiary alcohols as terminal reductants. Mechanistic evidence is presented, indicating that this catalytic radical reduction is achieved by a Ru-hydride intermediate formed by β-hydride elimination from a Ru-alkoxide species. A similar mechanism and Ru-hydride intermediate was previously reported to kill cancer cells with catalytic pro-oxidant effects. Therefore, our demonstration of catalytic antioxidant effects by the same type of intermediate reveals new potential therapeutic strategies and applications for catalytic systems that form Ru-hydride intermediates. PMID:27254303

  3. Green and scalable production of colloidal perovskite nanocrystals and transparent sols by a controlled self-collection process

    Science.gov (United States)

    Liu, Shuangyi; Huang, Limin; Li, Wanlu; Liu, Xiaohua; Jing, Shui; Li, Jackie; O'Brien, Stephen

    2015-07-01

    Colloidal perovskite oxide nanocrystals have attracted a great deal of interest owing to the ability to tune physical properties by virtue of the nanoscale, and generate thin film structures under mild chemical conditions, relying on self-assembly or heterogeneous mixing. This is particularly true for ferroelectric/dielectric perovskite oxide materials, for which device applications cover piezoelectrics, MEMs, memory, gate dielectrics and energy storage. The synthesis of complex oxide nanocrystals, however, continues to present issues pertaining to quality, yield, % crystallinity, purity and may also suffer from tedious separation and purification processes, which are disadvantageous to scaling production. We report a simple, green and scalable ``self-collection'' growth method that produces uniform and aggregate-free colloidal perovskite oxide nanocrystals including BaTiO3 (BT), BaxSr1-xTiO3 (BST) and quaternary oxide BaSrTiHfO3 (BSTH) in high crystallinity and high purity. The synthesis approach is solution processed, based on the sol-gel transformation of metal alkoxides in alcohol solvents with controlled or stoichiometric amounts of water and in the stark absence of surfactants and stabilizers, providing pure colloidal nanocrystals in a remarkably low temperature range (15 °C-55 °C). Under a static condition, the nanoscale hydrolysis of the metal alkoxides accomplishes a complete transformation to fully crystallized single domain perovskite nanocrystals with a passivated surface layer of hydroxyl/alkyl groups, such that the as-synthesized nanocrystals can exist in the form of super-stable and transparent sol, or self-accumulate to form a highly crystalline solid gel monolith of nearly 100% yield for easy separation/purification. The process produces high purity ligand-free nanocrystals excellent dispersibility in polar solvents, with no impurity remaining in the mother solution other than trace alcohol byproducts (such as isopropanol). The afforded stable

  4. Luminescence in colorless, transparent, thermally stable thin films of Eu3+ and Tb3+ beta-diketonates in hybrid inorganic-organic zinc-based sol-gel matrix.

    Science.gov (United States)

    Martins, Renata Figueredo; Silva, Rodrigo Ferreira; Gonçalves, Rogéria Rocha; Serra, Osvaldo Antonio

    2010-05-01

    Luminescent zinc-based hybrid inorganic-organic films with rare-earth (RE) complexes have been prepared using a non-alkoxide sol-gel process. The films were fabricated by the dip-coating method starting from zinc acetate dihydrate, rare earth chloride, lactic acid as hydrolytic catalyst, and anhydrous ethanol. The beta-diketones thenoylltrifluoroacetone (Httfa) and dibenzoylmethane (Hdbm) were used as ligands to Eu(3+) and Tb(3+), respectively. After deposition of the first layer, the films were fired at temperatures between 50 and 300 degrees C, in air. Photophysical properties such as excitation, emission and emission, lifetimes were determined for the films obtained in different conditions. Eu(3+)/ttfa and Tb(3+)/dbm films fired at 300 and 250 degrees C, respectively, are still transparent and gave rise to intense emission when excited through the ligand (antenna effect). PMID:20179997

  5. High voltage breakdown capabilities of high temperature insulation coatings for HTS and LTS conductors

    International Nuclear Information System (INIS)

    High temperature ZrO2 based coatings were deposited on Ag and Ag/AgMg sheathed Bi-2212 tapes from solutions derived from alkoxide-based precursors using a reel-to-reel, continuous sol-gel technique. The insulation coatings were annealed at 850 deg. C for 20 hours under O2 flow. The surface morphology and structure of coatings were characterized by SEM and XRD. High voltage breakdown of insulation on tapes was measured by a standard high voltage breakdown power supply. It has been found that high voltage breakdown values of these insulations strongly depend on number of dipping, thickness, coating type, annealing conditions, and dopant content in ZrO2. 20% Y2O3-ZrO2 coatings showed the best high voltage breakdown value, 2.05 kV at 1.5 mA

  6. Processing dependence of texture development in La2Zr2O7 buffer layer by sol-gel technique for YBCO coated conductors

    International Nuclear Information System (INIS)

    Perovskite textured La2Zr2O7 (LZO) films were deposited on Ni tapes using sol-gel process for fabrication of second generation high-Tc superconductors. LZO solutions were derived from acetate and alkoxide precursors. The effects of precursors, solvents, chelating agents, and annealing conditions (temperature and time), on epitaxial growth of LZO were investigated by XRD, SEM, EDS, and X-ray pole figure analysis. It was found that texture of LZO depended on, solution preparation, and annealing conditions. Textured, homogenous, dense, crack free and pinhole free, LZO films were produced on textured Ni tapes by postannealing at 1150 deg. C for 10 min under 4%H2-Ar gas flow when lanthanum (III) 2-methoxyethoxide precursor and 2-methoxyethanol solvent were used. When lanthanum acetate precursor and trifluoroacetic acid were used, texture was obtained at 1160 deg. C for 40 min annealing conditions

  7. Improvement in capacitive deionization function of activated carbon cloth by titania modification.

    Science.gov (United States)

    Ryoo, Min-Woong; Seo, Gon

    2003-04-01

    Activated carbon cloth (ACC) was modified by the reaction between polar groups on its surface and metal alkoxides of titanium, silicon, aluminum and zirconium to enhance its capacitive deionization (CDI) performance. Incorporated state of metals and surface property of modified ACC were deduced from surface analysis results obtained using FE-SEM, XRD, XPS and zeta-potential meter. Titania was highly dispersed on the ACC surface with tetrahedral coordination, and the incorporated titania was effective to decrease physical adsorption of NaCl and to increase electric field adsorption, resulting in a significant enhancement of CDI performance. The negligible contribution of silica, alumina and zirconia modifications suggested that the small oxidation-reduction potential of titania was responsible for the enhancement of the electric field adsorption. Reversibility of adsorption and desorption operation on titania-modified ACC were also discussed relating to its CDI function. PMID:12600380

  8. Fenilsilicato dopado com Eu III obtido pelo método sol-gel Phenylsilicate doped with Eu III obtained by sol-gel methodology

    Directory of Open Access Journals (Sweden)

    Eduardo J. Nassar

    2007-01-01

    Full Text Available In this work, we report the synthesis and the photoluminescence features of a Eu(III-doped modified silica matrix obtained by the sol-gel method. The matrix was prepared by reaction between tetraethylorthosilicate and phenyltriethoxysilane alkoxide. The hydrolysis occurred using basic catalysis. The solids were treated at 100, 200 and 300 ºC during 4 h and the structure was determined by thermogravimetric analysis (TG/DTG, nuclear magnetic resonance (NMR 29Si and 13C, infrared spectroscopy (IR and photoluminescence (PL. The PL spectra display the Eu(III lines characteristic of the ion, 5D0 -> 7F J (J=0, 1, 2, 3, 4, the blue emission as ascribed in the silica matrix. The NMR and TG showed the stability of hybrid silica.

  9. Stress engineering for the design of morphotropic phase boundary in piezoelectric material

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, Tomoya, E-mail: ohno@mail.kitami-it.ac.jp [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Yanagida, Hiroshi; Maekawa, Kentaroh [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Arai, Takashi; Sakamoto, Naonori; Wakiya, Naoki; Suzuki, Hisao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561 (Japan); Satoh, Shigeo [Graduate School of Science and Engineering, Ibaragi University, 4-12-1 Nakanarusawa-cho, Hitachi, Ibaragi 316-0033 (Japan); Matsuda, Takeshi [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan)

    2015-06-30

    Alkoxide-derived lead zirconate titanate thin films having Zr/Ti = 50/50 to 60/40 compositions with different residual stress conditions were deposited on a Si wafer to clarify the effects of the residual stress on the morphotropic phase boundary shift. The residual stress condition was controlled to − 0.1 to − 0.9 GPa by the design of the buffer layer structure on the Si wafer. Results show that the maximum effective piezoelectric constant d{sub 33} was obtained at 58/42 composition under − 0.9 GPa compressive residual stress condition. Moreover, the MPB composition shifted linearly to Zr-rich phase with increasing compressive residual stress. - Highlights: • The residual stress in lead zirconate titanate film on silicon was controlled. • The maximum residual stress in lead zirconate titanate film was − 0.9 GPa. • The morphotropic phase boundary shifted to zirconium rich phase by the strain.

  10. Continuous tubular flow reactor for XAFS studies of organometallic reactions: Possibilities and limitations for studies of the Soai reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nchari, Luanga N; Hembury, Guy A; Beesley, Angela M; Tsapatsaris, Nikolaos; Hudson, Matthew; Schroeder, Sven L M [School of Chemical Engineering and Analytical Science, University of Manchester, PO Box 88, Manchester, M60 1QD (United Kingdom); Meehan, David J; Thomason, Matthew, E-mail: s.schroeder@manchester.ac.u [School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2009-11-15

    A computer-controlled continuous tubular flow reactor system has been commissioned that permits time-resolved in situ XAFS measurements of organometallic reactions. The system was commissioned by Zn K-edge measurements of products formed during the Soai reaction. XANES data are shown that illustrate the quality of the data that can be achieved. The XANES spectra are compatible with the presence of dimer, trimer or other oligomeric alkoxide species in the Soai process. It is shown how heterogeneity in the Soai reaction system leads to considerable complications with the measurements due to the formation of floating particles of the aldehyde/iPr{sub 2}Zn adduct formed in the reaction; additionally, decomposition of iPr{sub 2}Zn with residual air and moisture leads to deposits on cell walls.

  11. PREPARATION OF POLYIMIDE-BaTiO3 HYBRID FILMS BY A DISPERSION PROCESS AND THEIR MICROSTRUCTURE

    Institute of Scientific and Technical Information of China (English)

    Yue-sheng Li; Yue-jin Tong; Kai Jing; Meng-xian Ding

    2001-01-01

    Barium titanate (BaTiO3) powders with particle sizes of 30~50 nm were prepared from barium stearate, titanium alkoxides and stearic acid by stearic acid-gel method. Dispersing the agglomerate of BaTiO3 nanoparticles into poly(amic acid) solution followed by curing led to the formation of polyimide hybrid films. The hybrid films were transparent and well distributed with BaTiO3 nanoparticles when the BaTiO3 content was less than 1 wt%. Highly loaded hybrid film containing 30 wt % BaTiO3 was tough, had a smooth surface and possessed much higher dielectric and piezoelectric constants than the parent polyimide.

  12. Continuous supercritical synthesis and dielectric behaviour of the whole BST solid solution

    International Nuclear Information System (INIS)

    In this study we show that pure and well crystallized nanoparticles of BaxSr1-xTiO3 (BST) can be synthesized over the entire range of composition through the hydrolysis and further crystallization of alkoxide precursors under supercritical conditions. To our knowledge, this is the first time that the whole ferroelectric solid solution has been produced in a continuous way, using the same experimental conditions. The composition of the powder can be easily controlled by adjusting the feed solution composition. The powders consist of soft-aggregated monocrystalline nanoparticles with an average particle size ranging from ∼20 to 40 nm. Ferroelectric ceramics with accurately adjustable Curie temperature (100-390 K) can thus be obtained by sintering

  13. Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Beletskiy, Evgeny V.; Hou, Xianliang; Shen, Zhongliang; Gallagher, James R.; Miller, Jeffrey T.; Wu, Yuyang; Li, Tiehu; Kung, Mayfair C.; Kung, Harold H.

    2016-03-17

    Mild calcination in ozone of a (POSS)-Sn- (POSS) complex grafted on silica generated a heterogenized catalyst that mostly retained the tetrahedral coordination of its homogeneous precursor, as evidenced by spectroscopic characterizations using EXAFS, NMR, UV-vis, and DRIFT. The Sn centers are accessible and uniform and can be quantified by stoichiometric pyridine poisoning. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. However, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn-O-Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions.

  14. Surface morphology engineering of metal-oxide films by chemical spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, J.; Solis, J.L.; Estrada, W. [Instituto Peruano de Energia Nuclear, Av. Canada 1470, San Borja, Lima (Peru); Facultad de Ciencias, Universidad Nacional de Ingenieria, P.O. Box 31-139, Lima (Peru); Gomez, M. [Facultad de Ciencias, Universidad Nacional de Ingenieria, P.O. Box 31-139, Lima (Peru)

    2007-07-01

    The Chemical Spray Pyrolysis technique and a combination of sol-gel and spray pyrolysis techniques have been used in order to monitor the morphology of metal-oxide-based thin films to be used as functional materials. We can obtain surfaces from specular to rough-porous according to the physico-chemical conditions of the precursor/spraying solution. We have produced coatings of ZnO-based and NiO{sub x}-based coatings from alcoholic and aqueous solutions. A single glass, ITO-precoated glass or alumina was used as the substrate. Porous materials of WO{sub 3}, WO{sub 3}-SnO{sub 2} and SnO{sub 2} have been produced by spraying either inorganic or metal alkoxide gels over a hot substrate. The morphologies of coatings were evaluated by either SEM or optical measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Enhanced electrical properties of ferroelectric thin films with electric field induced domain control

    International Nuclear Information System (INIS)

    (0 0 1) oriented Pb(Zr0.5Ti0.5)O3 (PZT) thin films with high piezoelectric constant were deposited by the electric field-assisted annealing (EFA-A) of alkoxide-derived precursor thin films. So far, selective orientation control of (0 0 1) domain and (1 0 0) domain is very difficult, especially for the chemical solution deposition (CSD). We tried an electric field induced domain control to improve the electrical properties with CSD. An electric field of 10 kV/cm has been applied during an annealing. The high (0 0 1) domain ratio of 75.6% was obtained from the deconvolution of (0 0 2) and (2 0 0) X-ray diffraction peaks. The PZT thin films showed very high piezoelectric constant of 352 pm/V. This shows electric field induced domain control is very effective to enhance the electrical properties of CSD-derived PZT thin films.

  16. Organometallic Gold(Ⅲ)Derivatives with Anionic Oxygen Ligands-mononuclear Hydroxo,Alkoxo,and Acetato Complexes:Synthesis and Spectral Study

    Institute of Scientific and Technical Information of China (English)

    Prithwiraj Byabartta

    2008-01-01

    A variety of gold(Ⅲ) adducts having a-ligated oxygen-donor ligands have been prepared from [Au(ppy)Cl2](ppy·phenylpyridine)(1) either by partial or total replacement of the chloride ions.The new species comprise hydroxo-[Au(ppy)(OH)Cl](2),and[Au(ppy)(OH)2](3),oxo-[Au2(ppy)2(μ-O)2](4),acetate-[Au(ppy)(O2CMe2)] (5),and alkoxo complexes-[Au(ppy)(OR)Cl](6,7)and[Au(ppy)(OR)2](8-10)(R=Me,6 and 8;Et,7 and 9;Pri,10).The dihydroxo and the OXO complexes Can be interconverted by refluxing the former in anhydrous THF and the latter in water.The hydroxides 2 and 3 and the acetato complex 5 undergo σ-ligand metathesis in ROH solution(R=Me,Et or Pri) to give the corresponding alkoxides.

  17. Thin film encapsulation for organic light-emitting diodes using inorganic/organic hybrid layers by atomic layer deposition.

    Science.gov (United States)

    Zhang, Hao; Ding, He; Wei, Mengjie; Li, Chunya; Wei, Bin; Zhang, Jianhua

    2015-01-01

    A hybrid nanolaminates consisting of Al2O3/ZrO2/alucone (aluminum alkoxides with carbon-containing backbones) grown by atomic layer deposition (ALD) were reported for an encapsulation of organic light-emitting diodes (OLEDs). The electrical Ca test in this study was designed to measure the water vapor transmission rate (WVTR) of nanolaminates. We found that moisture barrier performance was improved with the increasing of the number of dyads (Al2O3/ZrO2/alucone) and the WVTR reached 8.5 × 10(-5) g/m(2)/day at 25°C, relative humidity (RH) 85%. The half lifetime of a green OLED with the initial luminance of 1,500 cd/m(2) reached 350 h using three pairs of the Al2O3 (15 nm)/ZrO2 (15 nm)/alucone (80 nm) as encapsulation layers.

  18. Effect of chelating agent acetylacetone on corrosion protection properties of silane-zirconium sol-gel coatings

    Science.gov (United States)

    Yu, Mei; Liang, Min; Liu, Jianhua; Li, Songmei; Xue, Bing; Zhao, Hao

    2016-02-01

    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.

  19. Critical ageing and chemistry of nanocrystalline hydroxyapatite sol-gel solutions

    International Nuclear Information System (INIS)

    In previous work we have demonstrated that using alkoxide precursors, it is possible to produce crystalline hydroxyapatite coatings with potential uses in orthopaedic and dental applications. However, to produce monophasic hydroxyapatite coatings, sols must be aged for a minimum of 24 hours prior to deposition. 31P NMR has been used to analyse chemical changes occurring in the sol during the ageing process and have revealed that P-O-C bonds present in the precursor material are gradually replaced by P-O-Ca bonds with an accompanying change in oxidation state from P(III) to P(V). Thermal analysis was used to examine hydrolysed gels and showed that sols aged less than 24 hours contain unreacted calcium diethoxide which produces CaO upon heating. These findings have been confirmed by x-ray diffraction. Copyright (1998) Australasian Ceramic Society

  20. Influences of dehydrating process on properties of ATO nano-powders

    Institute of Scientific and Technical Information of China (English)

    吴湘伟; 陈振华; 黄培云

    2004-01-01

    Sb-doped SnO2 (ATO) nanometer powders were synthesized by hydrolysis of alkoxides, using SnCl4 ·5H2O and SbCl3 as raw materials. Some dehydrating processes, such as n-butanol/xylene mixed solvent heterogeneous azeotropic distillation, organic dehydrating agent and other dehydrating processes, were used to treat the wet colloids for preparing nonagglomerated ATO nanoparticles. The influences of dehydrating processes on the particle size, agglomeration and resistance were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmet-Teller (BET). It is indicated that the dehydrating methods have great influences on the products properties, and that n-butanol/xylene mixed solvent heterogeneous azeotropic distillation processing and organic dehydrating agent can effectively remove the residual H2O molecules in wet colloids, and be used to prepare powders with high surface areas, about 85.32 m2/g, low agglomeration and good conductivity.

  1. Study of refractive index and thickness of TiO2/ormosil planar waveguide

    Institute of Scientific and Technical Information of China (English)

    Wang Bao-Ling; Hu Li-Li

    2004-01-01

    Hybrid titania/ormosil waveguide films have been prepared by sol-gel method at low thermal treatment temperature of 150℃. The influence of processing parameters including the molar ratios of Ti(OBu)4/ glycidoxypropyltrimethoxysilane (GLYMO) and H2O/Ti(OBu)4 (expressed as R), especially aging of sol, on the refractive index and thickness of film was investigated. The optical properties of films were measured with Scanning Electron Microscope and m-line spectroscopy. The results indicate that the film thickness increases with the aging time of sol, but the variation of refractive index as a function of aging time of sol depends on the relative ratio of GLYMO to Ti-alkoxide.The relation between film thickness and corresponding sol viscosity is linear as the volume of GLYMO is 80% within the range of measured data.

  2. 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.

  3. Role of binder in the synthesis of titania membrane

    Indian Academy of Sciences (India)

    K S Seshadri; M Selvaraj; R Kesava Moorthy; K Varatharajan; M P Srinivasan; K B Lal

    2003-02-01

    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 an important role in that it not only helps in adjustment of sol viscosity but also helps in binding the sol particle with porous support. Here a comparative study on the role of different binders, viz. polyvinyl alcohol, polyethyleneimine, polyacrylamide, effect of their viscosity and surface tension effect on the morphology of the titania membrane is presented. The results show that among the three binders studied polyvinyl alcohol gave rise to membranes of desired characteristics when the sol viscosity was 0.08 pa.s.

  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...... treatment of Ti-MCM-41 in a ball mill or press did not influence the local environment around the titanium centers, whereas the MCM-41 structure was damaged causing a decrease of the conversion of cyclohexene....

  5. Synthesis and characterization of Al- and Ti-MCM-41 materials: application to oxidation of anthracene

    Directory of Open Access Journals (Sweden)

    R. S. Araújo

    2007-03-01

    Full Text Available The synthesis and characterization of new molecular sieves of the MCM-41 type are presented in this study. Samples were obtained from the alkoxides of Si, Ti and Al and different long-chain amine and alkylammonium salts surfactants, by the sol-gel method, through moderate agitation at room temperature. The reactions were conducted in two steps, acid hydrolysis (pH=2 and alkaline condensation (pH=10, both taking about 90min. The synthesized crystals were characterized using infrared spectroscopy, thermogravimetry and X-Ray diffraction. Pore diameters and surface areas were measured by N2 adsorption at 77K. Catalytic tests were conducted for anthracene oxidation using different oxidants (H2O2, alkylhydroperoxide and organic solvents (benzene, tetrahydrofuran.

  6. Photoinduced superhydrophilicity of amorphous TiOx-like thin films by a simple room temperature sol-gel deposition and atmospheric plasma jet treatment

    International Nuclear Information System (INIS)

    A room temperature sol gel process of TTIP / iPrOH / H2O /HNO3 sol was applied for the deposition of functional Ti alkoxide thin films on glass and polymeric substrates (PEEK). The unheated – amorphous films become superhydrophilic after 7 minutes of UV exposure which deteriorates after one day of storage in dark, exhibiting stable amphiphilic behavior. Superhydrophilicity is also obtained after 5 min of atmospheric pressure Ar – O2 plasma jet treatment. As the plasma power and the oxygen content of the mixture of the treatment increase (70W, 3.2 -5% O2) the films high hydrophilicity is maintained for many days even in dark atmospheric conditions providing long term hydrophilic coatings

  7. Atmospheric pressure chemical vapor deposition of ZnO: Process modeling and experiments

    International Nuclear Information System (INIS)

    The deposition of zinc oxide has been performed by atmospheric pressure chemical vapor deposition and trends in growth rates are compared with the literature. Diethylzinc and tertiary butanol were used as the primary reactants and deposition rates above 800 nm/min were obtained. The reaction kinetics were studied and detailed process modeling based on a reaction mechanism that includes the formation of an alkylzinc alkoxide intermediate product is discussed. This mechanism can explain the temperature dependent variety in deposition profiles observed in the static deposition experiments. The capability of modeling to gain insight in the local process conditions inside a reactor is demonstrated. - Highlights: • ZnO deposition at high rates of 800 nm/min • Modeling based on two step mechanism gives good fit. • Modeling gives insight in the inside of the reactor. • Modeling can even predict static deposition profiles

  8. 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.

  9. 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.

  10. 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.

  11. The Influence of Yttrium Isopropoxide on the Mechanical Properties of SiCW-reinforced AlN Ceramics

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using self-made metal-alkoxide yttrium isopropoxide as a sintering additive and disperser of whisker,the SiC whisker reinforced AlN ceramics was prepared.Its apparent density is 99.5 percent of the theoretical density;its flexural strength and fracture toughness are 681 MPa and 5.21 MPa*m1/2 respectively.Comparing the result with that by applying Y2O3 powder as a sintering additive,the flexural strength is increased by 25% and the fracture toughness is increased by 33%.The dispersity of whisker by increased yttrium isopropoxide is significantly better than that by Triton X-100.

  12. Nickel-aluminium complex: a simple and effective precursor for nickel aluminate (NiAl2O4 spinel

    Directory of Open Access Journals (Sweden)

    Apirat Laobuthee

    2008-01-01

    Full Text Available A reaction of aluminium hydroxide, nickel nitrate and triethanolamine in ethylene glycol provided, in one step, a simple and effective nickel-aluminium complex precursor for NiAl2O4 spinel. On the basis of 1H-, 13C-NMR spectroscopy, and mass spectrometry, the possible structure of the complex was proposed as a trimetallic double alkoxide consisting of two four-coordinate TEA-Al (alumatrane moieties linked via a bridging TEA group enfolding the Ni2+ cation. Transformation of the nickel-aluminium complex to pure spinel occurred when the complex precursor was pyrolysed at 1000C for 5 h. The BET surface area of the pyrolysed product was found to be 31 m2/g. In addition, the morphology of the powder product was examined by SEM.

  13. 4,5-Dihydro-1,2,3-oxadiazole: A Very Elusive Key Intermediate in Various Important Chemical Transformations.

    Science.gov (United States)

    Banert, Klaus; Singh, Neeraj; Fiedler, Benjamin; Friedrich, Joachim; Korb, Marcus; Lang, Heinrich

    2015-10-19

    4,5-Dihydro-1,2,3-oxadiazoles are postulated to be key intermediates in the industrial synthesis of ketones from alkenes, in the alkylation of DNA in vivo, and in the decomposition of N-nitrosoureas; they are also a subject of great interest for theoretical chemists. In the presented report, the formation of 4,5-dihydro-1,2,3-oxadiazole and the subsequent decay into secondary products have been studied by NMR monitoring analysis. The elusive properties evading characterization have now been confirmed by (1) H, (13) C, and (15) N NMR spectroscopy, and relevant 2D experiments at very low temperatures. Our experiments with suitably substituted N-nitrosoureas using thallium(I) alkoxides as bases under apolar conditions answer important questions on the existence and the secondary products of 4,5-dihydro-1,2,3-oxadiazole.

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

    Science.gov (United States)

    Joshi, Ashok V.; Balagopal, Shekar; Pendelton, Justin

    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.

  15. Method of making highly porous, stable aluminum oxides doped with silicon

    Energy Technology Data Exchange (ETDEWEB)

    Khosravi-Mardkhe, Maryam; Woodfield, Brian F.; Bartholomew, Calvin H.; Huang, Baiyu

    2016-03-22

    The present invention relates to a method for making high surface area and large pore volume thermally stable silica-doped alumina (aluminum oxide) catalyst support and ceramic materials. The ability of the silica-alumina to withstand high temperatures in presence or absence of water and prevent sintering allows it to maintain good activity over a long period of time in catalytic reactions. The method of preparing such materials includes adding organic silicon reagents to an organic aluminum salt such as an alkoxide in a controlled quantity as a doping agent in a solid state, solvent deficient reaction followed by calcination. Alternatively, the organic silicon compound may be added after calcination of the alumina, followed by another calcination step. This method is inexpensive and simple. The alumina catalyst support material prepared by the subject method maintains high pore volumes, pore diameters and surface areas at very high temperatures and in the presence of steam.

  16. Photoinduced superhydrophilicity of amorphous TiOx-like thin films by a simple room temperature sol-gel deposition and atmospheric plasma jet treatment

    Science.gov (United States)

    Vrakatseli, V. E.; Pagonis, E.; Amanatides, E.; Mataras, D.

    2014-11-01

    A room temperature sol gel process of TTIP / iPrOH / H2O /HNO3 sol was applied for the deposition of functional Ti alkoxide thin films on glass and polymeric substrates (PEEK). The unheated - amorphous films become superhydrophilic after 7 minutes of UV exposure which deteriorates after one day of storage in dark, exhibiting stable amphiphilic behavior. Superhydrophilicity is also obtained after 5 min of atmospheric pressure Ar - O2 plasma jet treatment. As the plasma power and the oxygen content of the mixture of the treatment increase (70W, 3.2 -5% O2) the films high hydrophilicity is maintained for many days even in dark atmospheric conditions providing long term hydrophilic coatings.

  17. E ective Doping of Rare-earth Ionsin Silica Gel:A Novel Approach to Design Active Electronic Devices

    Institute of Scientific and Technical Information of China (English)

    D. Haranath∗; Savvi Mishra; Amish G. Joshi; Sonal Sahai; Virendra Shanker

    2011-01-01

    Eu3+luminescence spectroscopy has been used to investigate the effective doping of alkoxide-based silica (SiO2) gels using a novel pressure-assisted sol-gel method. Our results pertaining to intense photolumi-nescence (PL) from gel nanospheres can be directly attributed to the high specific surface area and remarkable decrease in unsaturated dangling bonds of the gel nanospheres under pressure. An increased dehydroxylation in an autoclave resulted in enhanced red (∼611 nm) PL emission from europium and is almost ten times brighter than the SiO2 gel made at atmospheric pressure and∼50℃ using conventional St¨ober-Fink-Bohn process. The presented results are entirely different from those reported earlier for SiO2:Eu3+ gel nanospheres and the origin of the enhanced PL have been discussed thoroughly.

  18. Semiconducting of nanocrystalline tin oxide and its influence factors

    Institute of Scientific and Technical Information of China (English)

    LI Li-li; DUAN Xue-chen

    2005-01-01

    A series of nanocrystalline SnO2 powders, doped with different Sb contents, were synthesized by route of alkoxides hydrolysis using SnCl4·5H2O and SbCl3 as starting materials and calcined at different temperatures. The microstructure and morphology of samples are investigated by XRD and TEM, the valence state changes of Sb in SnO2 crystal lattice is detected by M(O)ssbauer spectroscopy and XPS.The resistivity of powders is examined with a mould of inside diameter d=10mm at a constant pressure. The results show that lightly-doping Sb is effective means of semiconducting of nanocrystalline SnO2. The ratio of Sb5+ to Sb3+ decreases with increasing Sb content in SnO2 crystal lattices and calcination temperature. The XPS diffraction confirms the same result as Mssbauer spectroscopy.

  19. 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.

  20. The formation of titanium dioxide crystallite nanoparticles during activation of PAN nanofibers containing titanium isopropoxide

    Energy Technology Data Exchange (ETDEWEB)

    Mehrpouya, Fahimeh; Tavanai, Hossein, E-mail: tavanai@cc.iut.ac.ir; Morshed, Mohammad [Isfahan University of Technology, Department of Textile Engineering, Center of Excellence in Applied Nanotechnology (Iran, Islamic Republic of); Ghiaci, Mehran [Isfahan University of Technology, Department of Chemistry (Iran, Islamic Republic of)

    2012-08-15

    Activated carbon (AC) can act as an important carrier for TiO{sub 2} nanoparticles. TiO{sub 2} nanoparticle can be fabricated by the hydrolysis and condensation of titanium alkoxides like titanium isopropoxide. This study showed that the formation of titanium dioxide crystallite nanoparticle during activation of PAN nanofibers containing titanium isopropoxide leads to the formation of mainly anatase crystal TiO{sub 2} nanoparticle in AC nanofibers, with a good dispersion in both the longitude and cross section of nanofibers. The TiO{sub 2} crystallite size lies in the range of 7.3-11.3 nm. The dispersion of TiO{sub 2} nanoparticles in the matrix of AC nanofibers is far superior to the direct mixing of TiO{sub 2} nanoparticles in the original electrospinning solution.

  1. Activity of B(OEt)3-MCM-41 catalyst in the MPV reduction of crotonaldehyde

    Indian Academy of Sciences (India)

    Burcu Uysal

    2013-11-01

    Mesoporous silica materialMCM-41 was functionalized with boron tri-ethoxide (B(OEt)3) groups by the grafting method and denoted as `B(OEt)3-MCM-41’. With the use of TEM, X-ray diffraction, highresolution thermogravimetry (TGA) and N2 adsorption-desorption isotherms, it was shown that the initial hexagonal structure, the high specific surface area, and porosity are retained in the functionalized material. 29Si NMR- and 11B NMR- spectroscopies revealed that the surface of MCM-41 consists of boron alkoxide species. The Meerwein-Ponndorf-Verley (MPV) reduction of crotonaldehyde to but-2-en-1-ol was conducted in the presence of B(OEt)3-MCM-41 catalyst. MPV reduction of crotonaldehyde also showed that functionalization leads to the creation of Lewis acidic sites. A combination of mesoporous structure with Lewis acidic properties makes the MCM-41 functionalized with boron tri-ethoxide groups, useful as solid Lewis acid catalysts.

  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. 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.

  4. Dinucleating Ligand Platforms Supporting Indium and Zinc Catalysts for Cyclic Ester Polymerization.

    Science.gov (United States)

    Kremer, Alexandre B; Osten, Kimberly M; Yu, Insun; Ebrahimi, Tannaz; Aluthge, Dinesh C; Mehrkhodavandi, Parisa

    2016-06-01

    The synthesis of the first alkoxide-bridged indium complex supported by a chiral dinucleating ligand platform (1), along with its zinc analogue (2), is reported. Both complexes are synthesized in a one-pot reaction starting from a chiral dinucleating bis(diamino)phenolate ligand platform, sodium ethoxide, and respective metal salts. The dinucleating indium analogue (7) based on an achiral ligand backbone is also reported. Indium complexes bearing either the chiral or achiral ligand catalyze the ring-opening polymerization of racemic lactide (rac-LA) to afford highly heterotactic poly(lactic acid) (PLA; Pr > 0.85). The indium complex bearing an achiral ligand affords essentially atactic PLA from meso-LA. The role of the dinucleating ligand structure in catalyst synthesis and polymerization activity is discussed. PMID:27187767

  5. Chiral Cobalt(III) Complexes as Bifunctional Brønsted Acid-Lewis Base Catalysts for the Preparation of Cyclic Organic Carbonates.

    Science.gov (United States)

    Rulev, Yuri A; Larionov, Vladimir A; Lokutova, Anastasia V; Moskalenko, Margarita A; Lependina, Ol'ga L; Maleev, Victor I; North, Michael; Belokon, Yuri N

    2016-01-01

    Stereochemically inert cationic cobalt(III) complexes were shown to be one-component catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa carbon dioxide pressure. The optimal catalyst possessed an iodide counter anion and could be recycled. A catalytic cycle is proposed in which the ligand of the cobalt complexes acts as a hydrogen-bond donor, activating the epoxide towards ring opening by the halide anion and activating the carbon dioxide for subsequent reaction with the halo-alkoxide. No kinetic resolution was observed when terminal epoxides were used as substrates, but chalcone oxide underwent kinetic resolution. PMID:26663897

  6. Synthesis and characterization of in situ prepared poly (methyl methacrylate) nanocomposites

    Indian Academy of Sciences (India)

    Shahzada Ahmad; Sharif Ahmad; S A Agnihotry

    2007-02-01

    Hybrid materials, which consist of organic–inorganic materials, are of profound interest owing to their unexpected synergistically derived properties. These hybrid materials replaced the pristine polymers due to their higher strength and stiffness in the recent years. In the present work, studies concerning the preparation of poly (methyl methacrylate) (PMMA), PMMA/SiO2, and PMMA/TiO2 nanocomposites are reported. These nanocomposite polymers were synthesized by means of free radical polymerization of methyl methacrylate using benzoyl peroxide as an initiator in a water medium. Further `sol–gel’ transformation based hydrolysis and condensation of Ti and Si alkoxides were used to prepare the inorganic phase during the polymerization process of MMA.

  7. Superficial modification of aluminium-base alloys (anodising and non-anodising) by silica coatings

    International Nuclear Information System (INIS)

    Transparent and colourless silica coatings were deposited on anadosing and non-anodising substrates of aluminium-base alloys (series 6063). Coatings were prepared by sol-gel (dipping method) from a silica alkoxide and a mixture of both silica alkolide and silica alkylalkoxide. Preparations were optimised from viscosity, density, surface tension, and contact angle measurements. Densification was carried out at 60 and 120 degree centigree. 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. (Author) 7 refs

  8. Synthetic Applications of Chiral Furanboronate

    Institute of Scientific and Technical Information of China (English)

    CHAN; KinFai

    2001-01-01

    We recently uncovered that consecutive reactions of chiral furfural-boronate 1 with a lithium alkoxide and a nucleophile led to the formation of alcohols 2 with good diastereoselection in favor of S-configuration at the newly generated chiral carbon. In addition, it was also found that 2a and 2b were chromatographically separable on a silica gel column. This reaction is believed to involve a tetrahedral borate intermediate, as can be substantiated by 11BNMR spectroscopic studies. Chiral furanmethanolboronates 2a(or 2b) underwent a palladium-catalyzed Suzuki coupling to form enantiomerically pure furans 3, which can be further converted to the synthetically useful hydroxypyranones 4.1,2,3 In addition, Mukaiyama reaction of 1 also led to chromatographically separable diastereomeric aldol-products. The scope and limitation of these conversions will be discussed.  ……

  9. Studies of methods to restrict the grain growth of nanocrystalline metal oxides

    CERN Document Server

    Al-Angari, Y

    2002-01-01

    There is considerable interest in nanocrystalline materials. This thesis is concerned with nanocrystalline oxides and the development of methods to prevent their grain growth on heating. This growth, which is evident at temperatures as low as 400 deg C, presents a serious problem in the study and applications of nanocrystalline oxides. The systems that were studied were nanocrystalline magnesium oxide, zirconium oxide, cerium oxide and tin oxide. The methods of preventing grain growth included the encapsulation of the oxide in the pores of porous silica, mixing with nanocrystals of alumina and treating the surface with a silanising agent, hexamethyldisilazane. All the methods employed showed some effect on reducing the grain growth. Encapsulation in the pores of silica was effective, however it proved difficult to get large amounts of the oxides into the pores. A more efficient method of preparing large samples was the incorporation of alumina, which was achieved by a sol-gel process. An alkoxide of the targe...

  10. 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.

  11. Preparation of 4-amino-2,4-dioxobutanoic acid

    Energy Technology Data Exchange (ETDEWEB)

    Unkefer, Pat J.; Martinez, Rodolfo A.; Glass, David R.

    2016-03-22

    A process for synthesizing 4-amino-2,4-dioxobutanoate involves reacting a dialkyl oxalate with an alkoxide in ethanol to form a reaction mixture, and afterward adding an alkyl cyano acetate to the reaction mixture and allowing a reaction to proceed under conditions suitable to form a first reaction product of the formula diethyl 2-cyano-3-hydroxy-butenedioate, and then isolating the diethyl 2-cyano-3-hydroxy-butenedioate, and afterward reacting the diethyl-2-cyano-3-hydroxy-butenedioate with an aqueous hydroxide under conditions suitable to form 4-amino-2,4-dioxobutanoate. The 4-amino-2,4-dioxobutanoate may be acidified into 4-amino-2,4-dioxobutanoic acid.

  12. Synthesis and Crystal Structures of Three Ladder Distannoxane Dimers [(PhCH2)2(Cl)SnOSn(X)(CH2Ph)2]2(X=Cl,OMe,OEt)

    Institute of Scientific and Technical Information of China (English)

    马春林; 李凤

    2003-01-01

    Three distannoxane dimers[(PhCH2)2(Cl)SnOSn(X)(CH2Ph)2]2(X=Cl,OMe,OEt)were prepared by the hydrolytic reaction of (PhCH2)2SnCl2 with sodium alkoxides.The compounds are assigned tetranuclear distannoxane structures in solid state.which contain the so-called ladder arrangement with a central planar Sn2O2 four-membered ring.The endo-and exo-cyclic Sn atoms are both five-coordinate,and have distorted trigonal bipyramidal geometries.A variety of hydrolyses of(PhCH2)2SnCl2 were performed and these dimers were characterized by IR,1H NMR spectroscopy and X-ray diffraction analysis.

  13. A new method for the chemoselective reduction of aldehydes and ketones using boron tri-isopropoxide, B(OPr)3: Comparison with boron tri-ethoxide, B(OEt)3

    Indian Academy of Sciences (India)

    Burcu Uysal; Birsen S Oksal

    2011-09-01

    A chemoselective Meerwein-Ponndorf-Verley reduction process of various aliphatic and allylic ,-unsaturated aldehydes and ketones is described. This chemoselective reduction is catalysed by boron triisopropoxide B(OPr)3. Kinetics of reduction of aldehydes and ketones to corresponding alcohols were also examined and rate constant of each carbonyl compounds were measured. Rate constant and reduction yield of each carbonyl compounds in the presence of B(OPr)3 were compared with those in the presence of B(OEt)3. The alcohols that are the reduction product were analysed by GC-MS. The rate constants and alcohol yields were found to be higher with B(OEt)3 than with B(OPr)3. The mechanism proposed involves a six-membered transition state in which both the alcohol and the carbonyl are coordinated to the same boron centre of a boron alkoxide catalyst.

  14. Maleimide Functionalized Siloxane Resins

    Energy Technology Data Exchange (ETDEWEB)

    Shaltout, R.M.; Loy, D.A.; Wheeler, D.R.

    1999-04-21

    In-situ filling through hydrolysis and condensation of silicon alkoxides has been utilized to generate nanocomposites in which the filler phase can be intimately associated with the polymer on relatively small length scales. One problem of the method has been achieving useful fill volumes without bulk phase separation of the reacting silicon monomer from the polymer. In this paper, we describe the preparation of a new class of nanocomposite materials in which the inorganic filler phase is pre-assembled before copolymerization with an organic species. Maleimide monomers, prepared from alkoxysilylpropyl amines and maleic anhydride, were protected against side reactions by forming the oxonorbornene Diels-Alder adduct with furan. The monomers were then reacted under sol-gel conditions to form oligomers or polymers-the filler phase. The material was activated by thermal deprotection of the maleimide and reacted with organic monomers or polymers to form the filled nanocomposite.

  15. Synthesis of TiO{sub 2} nanoparticles by hydrolysis and peptization of titanium isopropoxide solution

    Energy Technology Data Exchange (ETDEWEB)

    Mahata, S.; Mahato, S. S.; Nandi, M. M.; Mondal, B. [National Institute of Science and Technology, Palur Hills, Berhampur, Orissa (India); Centre for Advanced Material Processing, Central Mechanical Engineering Research Institute (CSIR-CMERI), Mahatma Gandhi Avenue, Durgapur- 713 209 (India); Dept. of Chemistry, National Institute of Technology, Durgapur (India)

    2012-07-23

    Here we report the synthesis and characterization of a stable suspension of modified titania nanoparticles. Phase-pure TiO{sub 2} nanocrystallites with narrow particle-size distributions were selectively prepared by hydrolysis-peptization of modified alkoxide followed by hydrothermal treatment. Autoclaving modified TiO{sub 2} in the presence of HNO3 as cooperative catalysts led to the formation of crystalline TiO{sub 2} with narrow-sized distribution. Following the hydrothermal treatment at 150 Degree-Sign C, X-ray diffraction shows the particles to be exclusively anatase. Synthesized powder is characterized by FT-IR, scanning electron microscopy (FESEM) and transmission electron microscopy (HRTEM). The photocatalytic activity in the degradation of orange-II is quite comparable to good anatase and rutile nanocrystallites.

  16. The derivation of a novel mitomycin skeleton: 3 alpha-alkoxymitomycin.

    Science.gov (United States)

    Kasai, M; Kono, M; Shirahata, K

    1991-03-01

    The first example of C-3 alkoxylation in mitomycins has been achieved. 3 alpha-iso-Propoxy-10-O-decarbamoylmitomycin D (4) and 3 alpha-iso-propoxymitomycin D (5) were derived from mitomycin D (3) under decarbamoylation conditions with iso-propoxide. Under similar conditions 3 alpha-iso-propoxy-10-O-decarbamoylporfiromycin (8) and 3 alpha-methoxy-10-O-decarbamoylmitomycin B (11) were also derived from porfiromycin (6) and mitomycin B (9), respectively. The mechanism of generation of these novel analogs was based on the premise that the key intermediate of hydroquinone iminium salt (14) was led through the iminium salt (13), followed by alkoxide addition and oxidation. PMID:2026556

  17. 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%.

  18. Effect of annealing temperature on titania nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, K., E-mail: sanjaymani367@gmail.com; Arumugam, S., E-mail: sanjaymani367@gmail.com [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli-620024 (India); Chandrasekaran, G. [Department of Physics, Pondicherry University, Pondicherry-605014 (India)

    2014-04-24

    Titania polycrystalline samples are prepared by using sol-gel route hydrolyzing a alkoxide titanium precursor under acidic conditions. The as prepared samples are treated with different calcination temperatures. The anatase phase of titania forms when treated below 600°C, above that temperature the anatase phase tends to transform into the rutile phase of titania. The experimental determination of average grain size, phase formation, lattice parameters and the crystal structures of titania samples at different calcinations is done using X-ray diffraction (XRD). Fourier Transform Infra-red Spectroscopy (FTIR), UV-vis-NIR spectroscopy and Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis X-ray are used to characterize the samples to bring impact on the respective properties.

  19. Method for synthesizing thin film electrodes

    Science.gov (United States)

    Boyle, Timothy J.

    2007-03-13

    A method for making a thin-film electrode, either an anode or a cathode, by preparing a precursor solution using an alkoxide reactant, depositing multiple thin film layers with each layer approximately 500 1000 .ANG. in thickness, and heating the layers to above 600.degree. C. to achieve a material with electrochemical properties suitable for use in a thin film battery. The preparation of the anode precursor solution uses Sn(OCH.sub.2C(CH.sub.3).sub.3).sub.2 dissolved in a solvent in the presence of HO.sub.2CCH.sub.3 and the cathode precursor solution is formed by dissolving a mixture of (Li(OCH.sub.2C(CH.sub.3).sub.3)).sub.8 and Co(O.sub.2CCH.sub.3).H.sub.2O in at least one polar solvent.

  20. Microstructure control in Si3N4 by particle coating

    International Nuclear Information System (INIS)

    Dense silicon nitride has been produced by hot-pressing silicon nitride powder with additions of Al2O3 and TiO2. The sintering aid was added by two methods: conventional oxide powder milling, and silicon nitride particle coating through the controlled hydrolysis of isopropanol solutions of aluminium and titanium alkoxides. The Al2O3-TiO2 system provides an active liquid, and yields dense material consisting of a low z-value β'-sialon containing nano-dispersion TiN, and larger grain silicon oxynitride. Better microstructural homogeneity is obtained by the use of coated powder than by conventional powder blending, as shown by the homogeneity dimensions of the Al and Ti distributions, microstructural observations, 4-point bend strength and Weibull modulus. (orig.)

  1. Surface morphology engineering of metal-oxide films by chemical spray pyrolysis

    International Nuclear Information System (INIS)

    Chemical spray pyrolysis technique and a combination of sol-gel and spray pyrolysis techniques have been used in order to monitor the morphology of metal-oxide-based thin films to be used as functional materials. We can get from specular to rough-porous surfaces according to the physical-chemical conditions of the precursor / spraying solution. We have produced coatings of ZnO-based and NiOx-based coatings from alcoholic and water solution. A single glass, ITO-precoated glass or alumina was used as the substrate. Porous materials of WO3, CuWO4-x and SnO2 have been produced spraying either inorganic or metal alkoxide gels over a hot substrate. Morphology of coatings were evaluated by either SEM or optical measurements. (author)

  2. Nanocasting of Periodic Mesoporous Materials as an Effective Strategy to Prepare Mixed Phases of Titania

    Directory of Open Access Journals (Sweden)

    Luther Mahoney

    2015-12-01

    Full Text Available Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO2(B. The mesoporous TiO2 materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO2(B exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy.

  3. Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide

    Indian Academy of Sciences (India)

    Akshai Kumar; Ashoka G Samuelson

    2012-11-01

    A theoretical study has been carried out at the B3LYP/LANL2DZ level to compare the reactivity of phenyl isocyanate and phenyl isothiocyanate towards titanium(IV) alkoxides. Isocyanates are shown to favour both mono insertion and double insertion reactions. Double insertion in a head-to-tail fashion is shown to be more exothermic than double insertion in a head-to-head fashion. The head-to-head double insertion leads to the metathesis product, a carbodiimide, after the extrusion of carbon dioxide. In the case of phenyl isothiocyanate, calculations favour the formation of only mono insertion products. Formation of a double insertion product is highly unfavourable. Further, these studies indicate that the reverse reaction involving the metathesis of N,N'-diphenyl carbodiimide with carbon dioxide is likely to proceed more efficiently than the metathesis reaction with carbon disulphide. This is in excellent agreement with experimental results as metathesis with carbon disulphide fails to occur. In a second study, multilayer MM/QM calculations are carried out on intermediates generated from reduction of titanium(IV) alkoxides to investigate the effect of alkoxy bridging on the reactivity of multinuclear Ti species. Bimolecular coupling of imines initiated by Ti(III) species leads to a mixture of diastereomers and not diastereoselective coupling of the imine. However if the reaction is carried out by a trimeric biradical species, diastereoselective coupling of the imine is predicted. The presence of alkoxy bridges greatly favours the formation of the d,l (±) isomer, whereas the intermediate without alkoxy bridges favours the more stable meso isomer. As a bridged trimeric species, stabilized by bridging alkoxy groups, correctly explains the diastereoselective reaction, it is the most likely intermediate in the reaction.

  4. 五烷氧基钽化合物的电化学合成及其应用性能研究%Research on the electrochemical synthesis and applied properties of tantalum pentaalkoxides

    Institute of Scientific and Technical Information of China (English)

    李淑娟; 鞠鹤; 蔡天晓; 孙晓红; 刘源发

    2011-01-01

    Aim To research for a novel method of synthesizing tantalum metallorganic compounds. Methods Three tantalum alkoxide compounds were synthesized by the electrochemical method using the metal tantalum as an anode. The high purity compounds had been got by distillation in the vacuum. Results Three compounds had been got. The structures of the compounds were confirmed by IR. The tests of impurity elements were analyzed by ICPAES. The purities of the compounds were more than 99.995%. Conclusion The reported method had many advantages of mild reaction conditions, easy operations and available purification. The application was studied in the coating of non-dissolved anode. The results of titanium anodes proved that the tantalum alkoxides can improve the electrochemical and enduring feature of the coating so as to enhance non-dissolved anode properties.%目的 研究合成金属钽有机化合物的新方法.方法 以金属钽为阳极,采用牺牲阳极的电化学法合成不同烷氧基的钽化合物,经过减压精馏得到高纯化合物.结果 合成了3种不同烷氧基的钽化合物,利用红外光谱对产物进行了结构表征,发射光谱进行了杂质元素分析测试,产品纯度达99.995%.结论 该方法具有反应条件温和、操作简便、易于纯化的优点,合成的高纯烷氧基钽可以有效改善不溶性阳极涂层的电化学性能和耐久性能,大大提高阳极的应用能力.

  5. Aluminum Complexes Stabilized by Piperazidine-Bridged Bis(phenolate) Ligands: Syntheses, Structures, and Applica- tion in the Ring-Opening Polymerization of ε-Caprolactone

    Institute of Scientific and Technical Information of China (English)

    李文艺; 姚英明; 张勇; 沈琪

    2012-01-01

    The synthesis and characterization of aluminum alkoxide and alkyl complexes stabilized by piperazidine- bridged bis(phenolate) ligands are described. Treatment of ligand precursors Hz[ONNO]^1 {Hz[ONNO]^1= 1,4-bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)piperazidine} and Hz[ONNO]2 {H2[ONNO]2=1,4-bis(2-hydroxy3,5-di-tert-butylbenzyl)piperazidine} with A1Et2(OCH2Ph) and A1Etz(OPr-i), which were generated in situ by the reactions of AIEt3 with equivalent of the corresponding alcohols, in a 1: 1 molar ratio in THF gave the corresponding aluminum alkoxide complexes [ONNO]IAI(OCH2Ph) (1) and [ONNO]2Al(OPr-i) (2), respectively. The reaction of H2[ONNO]^1 with A1Etz(OCHzPh) in a 1 : 2 molar ratio in THF afforded a mixture of monometallic aluminum ethyl complex [ONNO] 1A1Et (3) and complex 1, which can be isolated by stepwise crystallization. Similarly, Hz[ONNO]2 reacted with A1Etz(OPr-0 in a 1: 2 molar ratio in THF to give a mixture of aluminum ethyl complex [ONNO]2AlEt (4) and complex 2. Complexes 1 and 2 were also available via treatment of complexes 3 and 4 with 1 equiv, of benzyl alcohol and isopropyl alcohol, respectively. All of these complexes were fully characterized including X-ray structural determination. It was found that complexes 1 to 4 can initiate the ring-opening polymerization of e-caprolactone, and complexes 1 and 2 showed higher catalytic activity in comparison with com- plexes 3 and 4.

  6. Sol-gel synthesis and characterization of tetra-alkoxysilane and bridged-polysilsesquioxane materials in non-polar solvents

    Energy Technology Data Exchange (ETDEWEB)

    Yamanaka, S.A.; Martino, A.; Kawola, J.S.; Loy, D.A. [Sandia National Laboratories, Albuquerque, NM (United States)

    1996-10-01

    Although the sol-gel method has widely been used for the encapsulation of molecules in porous glass materials, the variety of dopants has been limited by the solvents used in processing. Polar solvents, such as ethanol, methanol or tetrahydrofuran, are typically added as cosolvents to prevent phase separation between the organic metal alkoxide and water. Non-polar solvents are generally not suitable for sol-gel processing since they are immicible with the aqueous phase. Our study increases the availability of solvents that may be used in sol-gel processing and therefore expands the range of molecules suitable for encapsulation. Here, we report a novel method for preparing both silica sol-gel materials and bridged-polysilsesquioxane materials in a non-polar, hydrocarbon solvent. The method involves the formation of an inverse micelle upon addition of the surfactant, didodecyldimethylammonium bromide, to toluene. The dynamic nature of the micelle allows sol-gel reactions to occur between water (soluble in the polar core of the micelle) and the metal alkoxide precursor (soluble in the solvent phase). Materials prepared by this technique have been characterized by nitrogen sorption porosimetry, SEM, solid state {sup 29}Si NMR, TGA and XRD. Photochemical conversion of technetium fluorides and oxyfluorides is largely uninvestigated. Because technetium was introduced into U.S. uranium enrichment plants, decommissioning and decontamination of these plants will involve technetium fluorides and oxyfluorides. Photochemical conversion of such compounds may facilitate waste minimization and cost avoidance goals during plant clean-up. Photochemical fluorination using ultraviolet photolysis of a mixture of fluorine and oxygen gases is an effective means of converting solid, nonvolatile fluorides of fight actinides, such as U, Np, and Pu, into volatile hexafluorides thereby removing surface radioactive contamination.

  7. Synthesis, structure and luminescent properties of lanthanide fluoroalkoxides.

    Science.gov (United States)

    Kuzyaev, D M; Balashova, T V; Burin, M E; Fukin, G K; Rumyantcev, R V; Pushkarev, A P; Ilichev, V A; Grishin, I D; Vorozhtsov, D L; Bochkarev, M N

    2016-02-28

    Alkoxides [Ln(OR)3(DME)]2 (R = CH(CF3)2, Ln = Sm (1), Yb (2)), [Ce(OR)3(Phen)]2 (3) (Phen = 1,10-phenanthroline), [Ce(OR′)3(DME)2]2 (R′ = C(CF3)3) (4), {Gd(OR′)3(DME)2} (5), {Ln2[O(CF3)2C–C(CF3)2O]3} (Ln = Ce (6), Gd (7)), {Ce2[O(CF3)2C–C(CF3)2O]3(Phen)2} (8), and {Ce[O(CF3)2C–C(CF3)2O][O(CF3)2–C(CF3)2OH](Phen)2} (9) were synthesized by the reactions of silylamides Ln[N(SiMe3)2]3 with respective fluorinated alcohols. The heterovalent trinuclear complex {Sm2(μ2-OR)3(μ3-OR)2Sm(OR)2(THF)2.5(Et2O)0.5} (10) was obtained by treatment of SmI2(THF)2 with ROK. The reaction of europium(II) and yttrium(III) silylamides with ROH afforded the heterobimetallic alkoxide {Eu2(μ2-OR)3(μ3-OR)2Y(OR)2(DME)2} (11) containing divalent europium. The molecular structures of 1, 2, 3, 9, 10 and 11 were determined by X-ray analysis. All the prepared cerium derivatives as well as the europium–yttrium isopropoxide upon UV excitation exhibited photoluminescence in the regions of 370–425 (for Ce3+) and 485 nm (for Eu2+) which was assigned to 4d→5f transitions. PMID:26795570

  8. 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.

  9. Surface characterization of the interfaces from plasma-polymerized acetylene films deposited onto cold-rolled steel for rubber-to-metal bonding

    Science.gov (United States)

    Rosales Lombardi, Pablo I.

    The molecular structure of the interface between plasma-polymerized acetylene films and steel was determined using in-situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates in microwave (MW) and radio frequency (RF)-powered reactors. The films deposited in RF-powered reactors were characterized in-situ using XPS and FTIR spectrometers that were interfaced directly to the reactors. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of monosubstituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. The rearrangement of the monomer molecules during plasma was also determined by optical emission spectroscopy (OES), where CH and C2 species predominated in the optical emission spectra. Bands were observed near 1020 and 885 cm-1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C-C-O-Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm-1 and attributed to carboxylate groups in the interface between films and the oxidized surface of the substrate. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interface during plasma polymerization of acetylene. Results from XPS showed that the surface of steel substrates consisted mostly of a mixture of Fe2O3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma-polymerization of acetylene, there was a tendency for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Natural rubber reacted with plasma-polymerized acetylene primers through unsaturated functional groups present in the film. The RAIR and XPS

  10. Hierarchical porous TiO{sub 2} thin films by soft and dual templating

    Energy Technology Data Exchange (ETDEWEB)

    Henrist, Catherine, E-mail: catherine.henrist@ulg.ac.be [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); University of Liege, Center for Applied Technology in Microscopy (CATmu), B6 Sart Tilman, Liege 4000 (Belgium); Dewalque, Jennifer [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); Cloots, Rudi [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium); University of Liege, Center for Applied Technology in Microscopy (CATmu), B6 Sart Tilman, Liege 4000 (Belgium); Vertruyen, Bénédicte; Jonlet, Jonathan; Colson, Pierre [University of Liege, Department of Chemistry, GREENMAT-LCIS, B6 Sart Tilman, Liege 4000 (Belgium)

    2013-07-31

    Hierarchical porous structures, with different pore sizes, including pores larger than 10 nm, constitute an important field of research for many applications such as selective molecule detection, catalysis, dye-sensitized solar cells, nanobiotechnology and nanomedecine. However, increasing the pore size logically results in the decrease of specific surface. There is a need to quantify and predict the resulting porosity and specific surface. We have prepared hierarchical porous TiO{sub 2} thin films either by surfactant templating (soft) or dual surfactant/nanospheres templating (soft/hard). They all show narrow, bimodal distribution of pores. Soft templating route uses a modified sol–gel procedure by adding a swelling agent (polypropylene glycol) to a precursor solution containing Ti alkoxide and block-copolymer surfactant. This scheme leads to very thin films showing high specific surface and bimodal porosity with diameters of 10 nm and 54 nm. Dual templating route combines a precursor solution made of Ti alkoxide and block-copolymer surfactant with polystyrene (PS) nanospheres (diam. 250 nm) in a one-pot simple process. This gives thicker films with a bimodal distribution of pores (8 nm and 165-200 nm). The introduction of PS nanospheres in the surfactant–Ti system does not interfere with the soft templating process and results in a macroporosity with a pore diameter 20–30% smaller than the original beads diameter. The dye loading of hierarchical films is compared to pure surfactant-templated TiO{sub 2} films and shows a relative decrease of 29% for soft templating and 43% for dual templating. The microstructure of bimodal porous films is characterized by several techniques such as transmission and scanning electron microscopy, X-ray diffraction, profilometry and ellipsometry. Finally, a geometrical model is proposed and validated for each system, based on the agreement between calculated specific surfaces and experimental dye loading with N719 dye

  11. The reactivity of metallic lithium toward solvents of relevance to energy storage: A surface science approach

    Science.gov (United States)

    Rendek, Louis Joseph, Jr.

    The reactivity of symmetric and asymmetric alkyl linear carbonates of the type ROCO2R', where R and R' represent methyl or ethyl groups, propylene carbonate (PC), gamma-butyrolactone (gamma-BL), dioxolane (DIOX) and tetrahydrofuran (THF) toward metallic Li was studied by infrared reflection absorption (IRAS), X-ray photoelectron (XPS) and Auger electron (AES) spectroscopies in ultrahigh vacuum (UHV). An identification of the products of these reactions may provide much needed insight into the physicochemical properties of passive films formed on Li electrodes, which are believed to be primarily responsible for controlling the performance of rechargeable Li batteries. Comparison of the IRAS and C(1s) and O(1s) XPS spectra of clean Li surfaces exposed to dimethyl (DMC), diethyl (DEC) and ethylmethyl carbonates (EMC) with those obtained in very similar experiments involving judiciously selected alcohols provided unambiguous evidence that the products of such reactions are primarily Li alkoxides (ROLi and RgammaOLi). Spectral evidence was also found for the presence of Li ethyl carbonate for experiments involving DEC and EMC, as well as Li oxide as judged by the occurrence of an O(1s) XPS peak at 530 eV. In the case of PC the IRAS and XPS spectra of PC/Li was found to be identical to that obtained by exposing Li to 1,2-propanediol vapors under otherwise identical conditions, and may thus be attributed to the corresponding alkoxide derivative. Unlike all other alkyl carbonates examined, the presence of a small amount of Li carbonate as a Li surface impurity led to the formation of detectable amounts of the Li alkyl carbonate derivative following exposure to PC. Similar experiments involving gamma-BL yielded IRAS and XPS features consistent with Li butyrate and a derivative of a cyclic beta-keto ester anion of Li as the main reaction products. The conclusions emerging from this study support by and large the mechanism proposed by Aurbach et al. for reactions between Li

  12. Sol-gel processing of metal sulfides

    Science.gov (United States)

    Stanic, Vesha

    Metal sulfides were synthesised via a sol-gel process using various metal alkoxides and hydrogen sulfide in toluene. Colloidal gels were prepared from germanium ethoxide, germanium isopropoxide, zinc tert-butoxide and tungsten (VI) ethoxide, whereas colloidal powder was produced from tungsten (V) dichloride ethoxide. Special precautions were necessary to protect the reaction mixture from water contamination which produced metal oxides. Results indicated that the main source of water is the hydrogen sulfide gas. In addition, synthesis of metal sulfides from a mixture of metal oxide and sulfide was demonstrated by the example of monoclinic germanium disulfide. It was produced by reaction of the sol-gel product with sulfur. Heat treatment of the sol-gel product and sulfur yielded single phase GeSsb2. The sol-gel prepared materials and their heat treated products were characterized by various methods. A chemical kinetics study of the functional groups -OR, -SH and Ssp{2-} was carried out for the sol-gel processing of GeSsb2 from of hydrogen sulfide and two different alkoxides, germanium ethoxide and germanium isopropoxide. The study was performed for different concentrations of precursors at different molar ratios and temperatures. The results indicate that the proposed reaction mechanism was simplified under appropriate reaction conditions. Experimentally determined rate constants of thiolysis and condensations demonstrate that thiolysis is slow and that condensations are fast steps, regardless of the studied reaction conditions. A study of the temperature effect on the reaction rate constant shows that it increases with temperature in accord with both Arrhenius law and transition-state theory. Activation energies, Esba, and activation parameters DeltaSsp{ddagger}, DeltaHsp{ddagger} and DeltaGsp{ddagger}, were determined for thiolysis and condensation reactions. The potentiometric tiration method was used for quantitative determination of germanium sulfide and

  13. Phosphonate Based High Nuclearity Magnetic Cages.

    Science.gov (United States)

    Sheikh, Javeed Ahmad; Jena, Himanshu Sekhar; Clearfield, Abraham; Konar, Sanjit

    2016-06-21

    Transition metal based high nuclearity molecular magnetic cages are a very important class of compounds owing to their potential applications in fabricating new generation molecular magnets such as single molecular magnets, magnetic refrigerants, etc. Most of the reported polynuclear cages contain carboxylates or alkoxides as ligands. However, the binding ability of phosphonates with transition metal ions is stronger than the carboxylates or alkoxides. The presence of three oxygen donor sites enables phosphonates to bridge up to nine metal centers simultaneously. But very few phosphonate based transition metal cages were reported in the literature until recently, mainly because of synthetic difficulties, propensity to result in layered compounds, and also their poor crystalline properties. Accordingly, various synthetic strategies have been followed by several groups in order to overcome such synthetic difficulties. These strategies mainly include use of small preformed metal precursors, proper choice of coligands along with the phosphonate ligands, and use of sterically hindered bulky phosphonate ligands. Currently, the phosphonate system offers a library of high nuclearity transition metal and mixed metal (3d-4f) cages with aesthetically pleasing structures and interesting magnetic properties. This Account is in the form of a research landscape on our efforts to synthesize and characterize new types of phosphonate based high nuclearity paramagnetic transition metal cages. We quite often experienced synthetic difficulties with such versatile systems in assembling high nuclearity metal cages. Few methods have been emphasized for the self-assembly of phosphonate systems with suitable transition metal ions in achieving high nuclearity. We highlighted our journey from 2005 until today for phosphonate based high nuclearity transition metal cages with V(IV/V), Mn(II/III), Fe(III), Co(II), Ni(II), and Cu(II) metal ions and their magnetic properties. We observed that

  14. Plutonium Immobilization Form Development Interim and Final Data Report Summaries

    Energy Technology Data Exchange (ETDEWEB)

    VanKonynenburg, R.; Ebbinghaus, B.

    2000-06-01

    Contained within this report are summaries of the available interim and final data summary reports provided by ANSTO, ANL, LLNL, and WSRC in support of work in the Form Development activity in the Plutonium Immobilization Development and Testing Program. Milestone reports and technical papers prepared for journals or conference proceedings are not included in this list. This document covers work from about 1997 to the present. All of the following reports are available from the Plutonium Immobilization Program Document Control Center (DCC) at LLNL. In most cases, the documents can also be obtained from the libraries the originating site or from the document's authors. All samples of the various formulations discussed in the following summaries were prepared by one of four processes: Wet-milling, dry-milling, an alkoxide-nitrate process, or attritor milling. The fabrication processes differ primarily in the mixing steps. The wet milling process is the one most commonly used. It is a simple ball milling process where water is added that provides intimate mixing of the materials. The dry milling process is a worst case dry mixing process. The alkoxide-nitrate process provides for very intimate mixing and is used when equilibrium samples are desired. The attritor milling process simulates the process being developed for the Plutonium Immobilization Plant. After mixing, the subsequent calcination and consolidation steps are generally the same. Most samples were consolidated by cold pressing and sintering although some of the earlier samples or Some of the single-phase samples were prepared by hot pressing. The sample identification numbers (ID's) that are referenced in the summaries (e.g. A-0, B3-13, etc.) are described in the Sample Test Matrix (PIP-99-012 and PIP-00-016). Samples which contain both plutonium and uranium are given the designation Hf-Pu-U samples. When Ce was used as a surrogate for Pu, the designation is Hf-Ce-U. When Th was used as a

  15. Synthesis, magnetic behaviour, and X-ray structures of dinuclear copper complexes with multiple bridges. Efficient and selective catalysts for polymerization of 2,6-dimethylphenol.

    Science.gov (United States)

    Murugavel, Ramaswamy; Pothiraja, Ramasamy; Gogoi, Nayanmoni; Clérac, Rodolphe; Lecren, Lollita; Butcher, Ray J; Nethaji, Munirathinam

    2007-06-21

    The use of a potentially tridentate mono-anionic bridging ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (bdmpp-H), in assembling new dimeric copper complexes with interesting magnetic properties has been investigated. The reaction of copper hydroxide or copper acetate with phenyl phosphinic acid or diphenyl phosphinic acid in the presence of bdmpp-H produces the dinuclear complexes [Cu(bdmpp)(ppi)]2 (1) and [Cu(bdmpp)(dppi-H)]2(dppi)2 (2) (ppi-H = phenylphosphinic acid: dppi-H = diphenylphosphinic acid), respectively. The products have been characterized with the help of analytical, thermal, and spectroscopic (IR, UV-vis, and EPR) techniques. Single crystal X-ray diffraction studies of 1 and 2 reveal that the two bdmpp ligands hold together the dimeric copper unit in each complex through mu-O alkoxide and the pyrazolyl nitrogen ligating centers. Two phenyl phosphinate ligands additionally bridge the dicopper core in 1 to result in octahedral coordination geometry around each metal ion. The diphenyl phosphinic acid acts as a terminal ligand in 2, and thus completes a square pyramidal geometry around each copper ion. Both complexes show a very short Cu...Cu separation (3.001 and 3.065 angstroms for 1 and 2, respectively). The investigation of the magnetic properties reveals the efficiency of the double alkoxide bridge between the two paramagnetic copper ions to mediate strong antiferromagnetic interactions [J/k(B) = -620(5) K (-431(4) cm(-1)) and -685(5) K (-476(4) cm(-1)) for 1 and 2, respectively]. Compounds 1 and 2, along with a few other copper phosphate complexes, were tested as catalysts for the oxidative polymerization of 2,6-dimethylphenol; 1 and 2 were found to be efficient catalysts with an increased selectivity for the formation of the polyphenylene ether. However a related mononuclear octahedral copper complex [Cu(imz)4(dtbp)2] (dtbp-H = di-tert-butylphosphate) was found to be more efficient. PMID:17844662

  16. 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

    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...

  17. 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.

  18. Single-component routes to perovskite phase mixed metal oxides

    International Nuclear Information System (INIS)

    This paper reports that crystalline perovskite phase mixed metal oxides have been prepared at low temperatures from single-component mixed metal-organic precursors specifically designed for this purpose. Pyridine solutions of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CMe2OH)2 where A = Pb, Ca, Sr, Ba: Me = methyl, react with metal alkoxide compounds such as B(OR')4, where B = Ti, Zr, Sn with the elimination of two equivalents of alcohol to form species with a fixed A:B stoichiometry of 1:1 according to the equation below. A(O2C(CMe2OH)2 + B(OR')4 > A(O2CCMe2O)2B(OR')2 + 2HOR'. Hydrolysis of these solutions with an excess of water results in homogeneous clear solutions from which white or pale yellow solids can be isolated, by evaporation of the volatile components in vacuo. Thermolysis at 350 degrees C in O2 resulted in formation of crystalline perovskite phase products for the representative examples PbTiO3, PbZrO3, BaTiO3 CaTiO3 and BaSnO3

  19. High dose thermoluminescence dosimetry performance of Sol-gel synthesized TiO2 phosphors

    International Nuclear Information System (INIS)

    Full text: TiO2 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 TiO2 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 TiO2 phosphors for dosimetric applications. The thermoluminescent characterization of samples was carried out after being exposed to beta particle irradiation. TiO2 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 TiO2 is a promising material to develop high dose Tl dosimeters. (Author)

  20. Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route.

    Science.gov (United States)

    Armelao, Lidia; Barreca, Davide; Bottaro, Gregorio; Maragno, Cinzia; Tondello, Eugenio; Caneschi, Andrea; Sangregorio, Claudio; Gialanella, Stefano

    2006-04-01

    Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxidic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size <30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.

  1. Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

    Science.gov (United States)

    Zu, Guoqing; Shen, Jun; Wang, Wenqin; Zou, Liping; Lian, Ya; Zhang, Zhihua

    2015-03-11

    Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (aerogels promising candidates as photocatalysts.

  2. From Fragile to Resilient Insulation: Synthesis and Characterization of Aramid-Honeycomb Reinforced Silica Aerogel Composite Materials

    Directory of Open Access Journals (Sweden)

    Marina Schwan

    2015-12-01

    Full Text Available The production of a new composite material embedding aramid honeycomb materials into nano-porous silica aerogels is studied. Our aim is to improve the poor mechanical strength of silica aerogels by aramid honeycombs without losing the amazing properties of the aerogels like little density and low thermal conductivity. The composite materials were prepared using two formulations of silica aerogels in combination with aramid honeycomb materials of different cell sizes. The silica aerogels are prepared using silicon alkoxides methyltrimethoxysilane and tetraethylorthosilicate as precursors in a two-step acid–base sol–gel process. Shortly in advance of the gelation point, the aramid honeycombs were fluted by the sol, gelation occurred and, after the aging process, the gel bodies were supercritically dried. The properties of the received composite materials are satisfying. Even the thermal conductivities and the densities are a bit higher than for pure aerogels. Most importantly, the mechanical strength is improved by a factor of 2.3 compared to aramid honeycomb materials and by a factor of 10 compared to the two silica aerogels themselves. The composite materials have a good prospective to be used as an impressive insulation material.

  3. 氧化铝气凝胶的研究进展%Research Progress in the Stugy of Alumina Aerogels

    Institute of Scientific and Technical Information of China (English)

    胡子君; 周洁洁; 陈晓红; 孙陈诚

    2009-01-01

    Al_2O_3气凝胶以其独特性质受到人们的广泛关注.本文就Al_2O_3气凝胶的结构、性质和制备方法进行了综述,制备方法包括铝醇盐的一步法、两步法和无机铝盐的滴加环氧丙烷法,其中滴加环氧丙烷法是制备高性能Al_2O_3气凝胶非常有发展潜力的方法之一.同时还介绍了纤维增强气凝胶、多组分及掺杂改性气凝胶.%Alumina aerogel had been paid great attention for its unique properties. The structure and various preparation methods of alumina aerogels had been summarized in this paper. The preparation methods included alumina alkoxide one step,two steps method and addition of propylene oxide method. The addition of propylene oxide method is one of the most potential route for the synthesis of high performance alumina aerogels. Fiber-reinforced, multiple cornponent and doped aerogels were also introduced.

  4. Atomic resolution structure of a lysine-specific endoproteinase from Lysobacter enzymogenes suggests a hydroxyl group bound to the oxyanion hole.

    Science.gov (United States)

    Asztalos, Peter; Müller, Astrid; Hölke, Werner; Sobek, Harald; Rudolph, Markus G

    2014-07-01

    Lysobacter enzymogenes lysyl endoproteinase (LysC) is a trypsin-type serine protease with a high pH optimum that hydrolyses all Lys-Xaa peptide bonds. The high specificity of LysC renders it useful for biotechnological purposes. The K30R variant of a related lysyl endoproteinase from Achromobacter lyticus has favourable enzymatic properties that might be transferrable to LysC. To visualize structural differences in the substrate-binding sites, the crystal structures of wild-type and the K30R variant of LysC were determined. The mutation is located at a distance of 12 Å from the catalytic triad and subtly changes the surface properties of the substrate-binding site. The high pH optimum of LysC can be attributed to electrostatic effects of an aromatic Tyr/His stack on the catalytic aspartate and is a general feature of this enzyme subfamily. LysC crystals in complex with the covalent inhibitor N(α)-p-tosyl-lysyl chloromethylketone yielded data to 1.1 and 0.9 Å resolution, resulting in unprecedented precision of the active and substrate-binding sites for this enzyme subfamily. Error estimates on bond lengths and difference electron density indicate that instead of the expected oxyanion a hydroxyl group binds to the partially solvent-exposed oxyanion hole. Protonation of the alkoxide catalytic intermediate might be a recurring feature during serine protease catalysis.

  5. 含铝PSBR复合橡胶的制备及其力学性能%PREPARATION AND MECHANICAL PERFORMANCE OF ALUMINIUM-CONTAINING PSBR COMPOSITE ELASTOMER

    Institute of Scientific and Technical Information of China (English)

    张明; 严长浩; 李幼荣; 中北里志; 井上真一; 本弘

    2001-01-01

    The pyridinium salt was prepared from viny lpyridine-SBR(PSBR) latex and propyl bromide in chloroform solution, which was reacted with aluminium alkoxide [Al(OR)3] and then the new aluminium-contai ning hybrid elastomer (Al-O-PSBR) had been obtained. After it is blend to natu ral rubber (NR), the new vulcanizates can be obtained which shows the better mec hanical properties, especially its shock resistance is remarkable. The correlati ve structure had been analyzed by use of FT-IR(ATR), NMR and other methods.%利用铝的醇盐与PSBR季铵盐乳液反应,制成含铝有机-无机杂化弹性体胶片,再与天然橡胶进行并用,制得含铝PSBR复合硫化胶。这种 复合硫化胶具有优良的力学性能和独特的抗震作用。用IR和NMR以及其它方法分析了其相关结构。

  6. 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.

  7. 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)

  8. Effective Sol-Gel Nanocoatings on ZnO Electrodes for Suppressing Recombination in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Shintaro Ueno

    2012-01-01

    Full Text Available Attempts have been made to improve the performance of dye-sensitized solar cells by forming metal-oxide nanocoating layers on ZnO electrodes by a sol-gel transformation. SiO2, Nb2O5, TiO2, or ZrO2 nanocoating layers could be formed by dipping ZnO films into metal alkoxide solutions of low concentrations and subsequent heat treatments. The performance of DSSCs using the coated ZnO electrodes depends strongly on the structure of coating layers such as the thickness and the surface coverage, which are significantly influenced by the coating conditions. In particular, SiO2 and Nb2O5 coating layers are effective to suppress the recombination by constructing the energy barrier at the ZnO/electrolyte interface and enhance energy conversion efficiency. It is found that the coating layers also hinder the grain growth of ZnO, contributing to the enhanced cell performance as well.

  9. Influence of catalyst on structural and morphological properties of TiO2 nanostructured films prepared by sol-gel on glass

    Institute of Scientific and Technical Information of China (English)

    Mehdi Alzamani; Ali Shokuhfar; Ebrahim Eghdam; Sadegh Mastali

    2013-01-01

    Transparent TiO2 thin films have been prepared by the sol-gel method using titanium alkoxides as precursors. Thin films were deposited on glass supports by the dip-coating technique. The TiO2 layer acts as a self-cleaning coating generated from its photocatalysis and photoinduced superhydrophilicity. The crystalline structure of TiO2 films was dominantly identified as the anatase phase, consisted of uniform spherical particles of about 14-50 nm in size, which strongly depends upon catalyst-type and heat treatment temperature. Increasing heat treating temperature can lead to an increase in crystalline size. The results indicated that the sample S.S (sample derived from sol containing sulfuric acid as catalyst) exhibits superhydrophilic nature and better photocatalytic activity, which can be attributed to its higher anatase content and lower crystalline size. Morphological studies, carried out using Atomic Force Microscopy (AFM), confirm the presence of crystalline phase with such a grain size and low surface roughness. Thus, the applied films exhibiting high photocatalytic activity, superhydrophilic behavior, and low surface roughness can be used as an efficient self-cleaning coating on glass and other optical applications.

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

    International Nuclear Information System (INIS)

    In this work the results of studying the thermoluminescent properties (Tl) of the zirconium oxide in its amorphous state (ZrO2-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-H3 and Zr-O2. 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 ZrO2-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 ZrO2-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)

  11. 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.

  12. Sol-gel derived titania hybrid thin films with high refractive index

    International Nuclear Information System (INIS)

    Incorporation of metal alkoxides into polymers through sol-gel process is of significant interest for tuning the refractive index of optical materials. In this paper, the organic-inorganic hybrid material with high refractive index (RI) and transparency was studied. Tetrabutoxytitanate (TBOT) and alkoxysilanes including diphenyldimethoxysilane (DPS) and γ-glycidoxypropyl trimethoxysilane (GPTS) were employed as sources of the titania sol and the silica sol, respectively. Two series of titania-based inorganic-organic hybrid materials with and without acetylacetone (AcAc) were prepared using the sol-gel method. Subsequently, crack-free films were fabricated by spin coating. The hybrid films with different Ti content were characterized by various techniques including IR, UV-vis, TG/DSC, SEM and auto-laser ellipsometer. The results indicated that the hybrid films displayed homogeneous morphology and titania was crosslinked with alkoxysilanes. Films without AcAc showed higher optical transparency in the visible region than those containing AcAc. The RI of films without AcAc increased from 1.54 to 1.64 at 633 nm with Ti molar fraction varying from 10 to 70%. Whereas, in the films with AcAc, the refractive indices were higher and unorderly. The study has demonstrated great potential to obtain titania hybrid films with high RI and transparency.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kueper, T.W.

    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.

  14. 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.

  15. Influence of sol-gel parameters on the properties of chemical optodes. Application to on-line analysis of high acidities

    International Nuclear Information System (INIS)

    An optical chemical sensor (optode) has been optimized to control high acidity levels (ranging from 1 to 10 N) of solutions from nuclear fuel reprocessing. The sol-gel process has been used successfully to prepare a porous silica layer doped with an indicator called Chromoxane Cyanine R (CCR). The sensor response represents changes in the absorption properties of the dye according to the acidity. In a first step, the leaching of the dye has been studied according to the sol-gel parameters. An experimental Hadamard matrix has been used to find the most influent parameters. The influent parameters resulting from the first step have been studied using a parametrical optimization based on a Doelhert experimental design. This optimization highlights a quantitative correlation between sensor response and the chemical parameters. Results indicate that the most suitable microporous xerogel films are those prepared using tetramethoxysilane at a pH set below the isoelectric point (lEP) of silica. The two other influent parameters are: water / alkoxide ratio (R) and aging temperature (Ta). The optimized values are R = 4 and Ta= 55 C. The lifetime of the sensor tested in a permanent circulation has been increased from several days to over 6 months in a 8 N nitric acid solution. Furthermore, this sensor can be used with hydrochloric and perchloric acids. (author)

  16. Mesoporous zirconium titanium oxides. Part 2: Synthesis, porosity, and adsorption properties of beads.

    Science.gov (United States)

    Sizgek, G Devlet; Sizgek, Erden; Griffith, Christopher S; Luca, Vittorio

    2008-11-01

    Mesoporous zirconium titanium mixed-oxide beads having disordered wormhole textures and mole fractions of Zr (x) ranging from x=0.25 to 0.67 have been prepared. The bead preparation method combined the forced hydrolysis of mixtures of zirconium-titanium alkoxides in the presence of long-chain carboxylates with external gelation. Uniformly sized beads could be produced in the size range 0.5-1.1 mm by varying the droplet size and viscosity of the mixed-oxide sol, thus making them suitable for large-scale column chromatographic applications. The beads exhibited narrow pore size distributions with similar mean pore diameters of around 3.7 nm. The specific surface areas of the beads were linked to the Zr mole fraction in the precursor solution and were generally greater than 350 m2/g for x=0.5. A combination of scanning transmission electron microscopy and X-ray absorption fine structure analysis indicated that the pore walls of the beads were composed of atomically dispersed Zr and Ti to form a continuous network of Zr-O-Ti bonds. Mass transport in the beads was evaluated by monitoring the kinetics of vanadate and vanadyl adsorption at pH 10.5 and 0.87, respectively. PMID:18828618

  17. Dielectric properties of lead zirconate titanate thin films seeded with barium strontium titanate nanoparticles

    International Nuclear Information System (INIS)

    A low temperature synthetic method recently proposed by the authors was applied to the fabrication of lead zirconate titanate (PZT) thin films containing crystalline seeds of barium strontium titanate (BST) nanoparticles. PZT precursor and the BST particles were prepared with complex alkoxide methods. Precursor solution suspending the BST particles was spin-coated on Pt/Ti/SiO2/Si substrate to film thickness of 500-800 nm at particle concentrations of 0-25.1 mol%, and annealed at various temperatures. Seeding of BST particles prevented the formation of pyrochlore phases, which appeared at temperatures above 400 deg. C in unseeded PZT films, and induced crystallization of PZT into perovskite structures at 420 deg. C, which was more than 100 deg. C below the crystallization temperature of the unseeded PZT films. Measurement of dielectric properties at 1 kHz showed that the 25.1 mol% BST-seeded PZT films annealed at 450 deg. C had a dielectric constant as high as 300 with a dissipation factor of 0.05. Leakage current density of the film was less than 1x10-6 A/cm2 at applied electric field from 0 to 64 kV/cm

  18. 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)

  19. Facile O-H bond activation in alcohols by [Cp*RuCl((I)Pr2PSX)] (X = pyridyl, quinolyl): a route to ruthenium(IV) hydrido(alkoxo) derivatives.

    Science.gov (United States)

    Jiménez-Tenorio, Manuel; Puerta, M Carmen; Valerga, Pedro

    2011-12-19

    The complexes [Cp*RuCl((i)Pr(2)PSX)] (X = pyridyl, quinolyl) react directly with alcohols ROH (R = Me, Et, (i)Pr, (n)Pr) and NaBPh(4), affording the novel cationic hydrido(alkoxo) derivatives [Cp*RuH(OR)((i)Pr(2)PSX)][BPh(4)]. These ruthenium(IV) compounds result from the formal oxidative addition of the alcohol to the 16-electron fragment {[Cp*Ru((i)Pr(2)PSX)](+)}, generated in situ upon chloride dissociation. The hydrido(alkoxo) complexes are reversibly deprotonated by a strong base such as KOBu(t), yielding the neutral alkoxides [Cp*Ru(OR)((i)Pr(2)PSX)], which are remarkably stable toward β elimination and do not generate the corresponding hydrides. The hydrido(alkoxo) complexes undergo a slow electron-transfer process, releasing H(2) and generating the dinuclear ruthenium(III) complex [{Cp*Ru(κ(2)-N,S-μ S-SC(5)H(4)N)}(2)][BPh(4)](2). In this species, the Ru-Ru separation is very short and consistent with what is expected for a Ru≡Ru triple bond. PMID:22087635

  20. 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.

  1. Thermochemical water decomposition cyle for hydrogen production%热化学循环分解水制氢

    Institute of Scientific and Technical Information of China (English)

    杨运嘉

    2001-01-01

    the thermochemical water decomposition cycle which consists of four gas-solid reaction of ca and Fe compounds for hydrogen production is discussed. The reactivity was improved by the introduction as a preparation method of the alkoxide and addition of graphite and lauric acid. Fine reactant Fe2O3 particles were homogeneously dispersed in the porous matrix of inert FeaTiOs with the sufficient strength of pellet.%文章所讨论的热化学循环分解水制氢是由Ca和Fe化合物的四步气-固反应所组成。在制备方法上,通过引入醇盐法并添加石墨和月桂酸将反应物Fe2O3颗粒均匀地分散在作为粘合剂的多孔惰性Fe2TeO5基质中,做成具有足够强度的丸,而使反应性得到改进。

  2. Study on the effects of complex ligands in the synthesis of TiO{sub 2} nanorod arrays using the sol-gel template method

    Energy Technology Data Exchange (ETDEWEB)

    Attar, A Sadeghzadeh; Mirdamadi, Sh [Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Ghamsari, M Sasani; Hajiesmaeilbaigi, F [Solid State Lasers Research Group, Laser and Optics Research School, Tehran 11365-8486 (Iran, Islamic Republic of); Katagiri, K; Koumoto, K [Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)], E-mail: mirdamadi@iust.ac.ir

    2008-08-07

    This work reports the effects of complex ligands on the synthesis of TiO{sub 2} nanorod arrays prepared by the improved sol-gel template method. In this method, the obtained TiO{sub 2} sols from the sol-gel process were injected by a syringe into the templates and then the samples were immediately immersed into boiling TiO{sub 2}-sol solutions. Densely and directionally aligned anatase nanorods of about 80-130 nm diameter and a length of several micrometres were successfully fabricated using an optimal molar ratio of the TiO{sub 2} sol. The results show that the molar ratio of the TiO{sub 2} sol plays an important role in the morphology and structure of TiO{sub 2} nanorods. The reaction between titanium alkoxide and acetylacetone leads to the formation of complex compounds, which can prevent the precipitation of undesired phases from the highly reactive precursors. These complex ligands can be removed after annealing at various temperatures, which depend on the molar ratio of the TiO{sub 2} sol.

  3. Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

    Directory of Open Access Journals (Sweden)

    Muhammad Raz

    2016-03-01

    Full Text Available Ca2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21 symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr and the coercive field (Ec were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF and activation energy (1.39 eV of the grain boundary was greater than the capacitance (5.7 pF and activation energy (1.13 eV of the grain.

  4. A silica sol-gel design strategy for nanostructured metallic materials.

    Science.gov (United States)

    Warren, Scott C; Perkins, Matthew R; Adams, Ashley M; Kamperman, Marleen; Burns, Andrew A; Arora, Hitesh; Herz, Erik; Suteewong, Teeraporn; Sai, Hiroaki; Li, Zihui; Werner, Jörg; Song, Juho; Werner-Zwanziger, Ulrike; Zwanziger, Josef W; Grätzel, Michael; DiSalvo, Francis J; Wiesner, Ulrich

    2012-03-18

    Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals--including noble metals--to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm(-1). This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

  5. Preparation and tribological properties of inclusion complex of β-cyclodextrin/dialkyl pentasulfide as additive in PEG-600 aqueous solution

    International Nuclear Information System (INIS)

    The inclusion complex of β-cyclodextrin (β-CD) and dialkyl pentasulfide (DPS), in which DPS was incorporated into β-CD cavities, was prepared by a co-precipitation method. The tribological properties of the complex used as lubricant additive in PEG 600 aqueous solution were investigated by a four-ball tester. The complex exhibited better tribological properties than β-CD under different loads, and also showed better anti-friction performance than DPS in the latter half of the test duration. The tribological action mechanism of the complex on a steel surface was studied according to the X-ray photoelectron spectroscopy (XPS) analyses. The β-CD molecules of the complexes were decomposed into various molecular fragments and the DPS molecules were released under the friction condition. It revealed that thiolate and ferrous sulfide (FeS) films formed by DPS played a major role, and iron alkoxide and carbon deposition films formed by the friction fragments of β-CD mainly exhibited anti-friction property on FeS-to-FeS interface. The interactions among different films led to the formation of a mixed boundary lubrication film.

  6. Preparation of Water-Repellent Glass by Sol-Gel Process Using Perfluoroalkylsilane and Tetraethoxysilane.

    Science.gov (United States)

    Jeong, Hye-Jeong; Kim, Dong-Kwon; Lee, Soo-Bok; Kwon, Soo-Han; Kadono, Kohei

    2001-03-01

    Coating films on glass substrate were prepared by sol-gel process using alkoxide solutions containing perfluoroalkylsilane (PFAS) and tetraethoxysilane (TEOS). The physical properties of the coating films were characterized by SEM, FT-IR, and XRD. And their surface properties were investigated by measuring contact angles and atomic compositions. Transparent coating films with smooth surface and uniform thickness could be obtained. The contact angles of the coating films for water and methylene iodide are extremely high, at 118 degrees and 97 degrees, respectively, and their surface free energies are about 9.7 dyn/cm. It was found that the water-repellent glass prepared is very hydrophobic and exhibits excellent water-repellency. Hydrophobic perfluoroalkyl groups are preferentially enriched to the outermost layer at the coating film-air interface, and two layers probably exist in the coating film. The upper layer oriented toward the air is composed of mainly perfluoroalkyl groups originating from PFAS, and the lower layer is composed of mainly -OSiO- groups originating from TEOS. The heat treatment after drying step cannot influence the surface enrichment of the perfluoroalkyl group. The hydrolysis reaction should be more completely done before the dip coating step to obtain lower surface free energy. The burning temperature should be less than 300 degrees C because the perfluoroalkyl group begins to decompose from this temperature. Copyright 2001 Academic Press.

  7. Thermally activated conversion of a silicate gel to an oxyfluoride glass ceramic: Optical study using Eu3+ probe ion

    International Nuclear Information System (INIS)

    Sol–gel route using metal alkoxides precursor and trifluoroacetic acid as in situ fluorination reagent has been used to prepare Eu3+-doped silicate xerogel, followed by thermal annealing to obtain oxyfluoride glass ceramic containing Eu3+-doped BaF2 nanocrystals. We have used Eu3+ as probe ion and we analyzed its characteristic features (photoluminescence, optical absorption and magnetic circular dichroism) to get information about the local environment around the ion during thermally activated evolution of the sol to xerogel and then glass ceramic. As the drying and annealing proceeds silica network is formed accompanied by precipitation of the nanofluoride crystalline phase; Eu3+ coordination changes gradually from a random and assymetric CF3COO- one (in the sol) to a symmetric one (in the BaF2 nanocrystals) given by the fluorine ions. Glass ceramization is based on a homogenous crystallization mechanism with BaF2 nucleation centres resulted from thermal decomposition of Ba-trifluoacetate at around 300 °C followed by subsequent growth into BaF2 nanocrystals above 600 °C; Eu3+-ions are incorporated during the nanocrystals growth. -- Highlights: • Glass ceramization is the result of a homogenous crystallization with BaF2 nucleation centres. • Eu3+-ions are incorporated during nanocrystals growth, above 600 °C. • Eu3+-ions are embedded dominantly in the BaF2 nanocrystals in high symmetry sites

  8. Water concentration controlled hydrolysis and crystallization in n-octanol to TiO2 nanocrystals with size below 10 nm

    International Nuclear Information System (INIS)

    Highlights: → Controlled hydrolysis of alkoxide was realized by adjusting water concentration. → Carrying out hydrolysis under different water concentration gave hydrolyzed intermediate with different composition. → A precise size control below 10 nm for anatase TiO2 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 TiO2 nanocrystals (NCS) were prepared with precise size control below 10 nm. The hydrolysis rate at different water concentration (Cwater) 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 Cwater. Powder X-ray diffraction (XRD) technique was used to track the crystallization process of TiO2 NCS. Transmission electron microscopy (TEM), XRD, FT-IR and TG/DTA techniques were used to characterize the particular properties of NCS. The Cwater 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.

  9. Structure and Reactivity of Alucone-Coated Films on Si and Li(x)Si(y) Surfaces.

    Science.gov (United States)

    Ma, Yuguang; Martinez de la Hoz, Julibeth M; Angarita, Ivette; Berrio-Sanchez, Jose M; Benitez, Laura; Seminario, Jorge M; Son, Seoung-Bum; Lee, Se-Hee; George, Steven M; Ban, Chunmei; Balbuena, Perla B

    2015-06-10

    Coating silicon particles with a suitable thin film has appeared as a possible solution to accommodate the swelling of silicon upon lithiation and its posterior cracking and pulverization during cycling of Li-ion batteries. In particular, aluminum alkoxide (alucone) films have been recently deposited over Si anodes, and the lithiation and electrochemical behavior of the system have been characterized. However, some questions remain regarding the lithium molecular migration mechanisms through the film and the electronic properties of the alucone film. Here we use density functional theory, ab initio molecular dynamics simulations, and Green's function theory to examine the film formation, lithiation, and reactivity in contact with an electrolyte solution. It is found that the film is composed of Al-O complexes with 3-O or 4-O coordination. During lithiation, Li atoms bind very strongly to the O atoms in the most energetically favorable sites. After the film is irreversibly saturated with Li atoms, it becomes electronically conductive. The ethylene carbonate molecules in liquid phase are found to be reduced at the surface of the Li-saturated alucone film following similar electron transfer mechanisms as found previously for lithiated silicon anodes. The theoretical results are in agreement with those from morphology and electrochemical analyses. PMID:25985821

  10. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    L M Manocha; E Yasuda; Y Tanabe; S Manocha; D Vashistha

    2000-02-01

    Carbon incorporation into the silicate network results in the formation of rigid carbidic glasses with improved physical, mechanical and thermal properties. This generated great interest in the development of these heteroatom structured materials through different processing routes. In the present studies, sol–gel processing has been used to prepare silicon based glasses, especially oxycarbides through organic–inorganic hybrid gels by hydrolysis–condensation reactions in silicon alkoxides, 1,4-butanediol and furfuryl alcohol with an aim to introduce Si–C linkages in the precursors at sol level. The incorporation of these linkages has been studied using IR and NMR spectroscopy. These bonds, so introduced, are maintained throughout the processing, especially during pyrolysis to high temperatures. In FFA–TEOS system, copolymerization with optimized mol ratio of the two results in resinous mass. This precursor on pyrolysis to 1000°C results in Si–O–C type amorphous solid black mass. XRD studies on the materials heated to 1400°C exhibit presence of crystalline Si–C and cristobalites in amorphous Si–O–C mass. In organic–inorganic gel system, the pyrolysed mass exhibits phase stability up to much higher temperatures. The carbidic materials so produced have been found to exhibit good resistance against oxidation at 1000°C.

  11. Development Of HUD Combiner For Automotive Windshield Application

    Science.gov (United States)

    Hattori, Akimasa; Makita, Kensuke; Okabayashi, Shigeru

    1989-12-01

    The head-up display system (HUM) has been developed for the windshield of Nissan Motor's passenger car, '88 model of Silvia (240SX) and '89 model of Maxima. HUD consists of a projector with high brightness VFT and a combiner which is a light-selective reflective film applied on the surface of ' e windshield. The system provides nice display legibility of speed in a three-digit reap at the position more than one meter far from driver's eye even under the bright sunlight. In this report, we present the optical properties and manufacturing process of the advanced combiner. The combiner has to have high transmittance as well as high reflectance so that a driver can see both foreground object and display reading at the same time. The optical design for the combiner is based on the concepts: (a) Visible light transmittance has to be 70% or more in accordance with a legal requirement, and (b) taking both peak wavelengths of Vim' and sensitivity characteristics of human eyes into consideration, 530nm of wave length is chosen as a reflective light. The combiner consists of a dielectric thin layer of Ti02-Si02 system. Its basic structure is decided by simulation with matrix method of the resultant waves. The coating film is applied on the restricted area of the forth surface of laminated windshield by newly developed solgel printing process using a metal alkoxide solution with a relatively long storage life.

  12. Preparation of Water-Repellent Glass by Sol-Gel Process Using Perfluoroalkylsilane and Tetraethoxysilane.

    Science.gov (United States)

    Jeong, Hye-Jeong; Kim, Dong-Kwon; Lee, Soo-Bok; Kwon, Soo-Han; Kadono, Kohei

    2001-03-01

    Coating films on glass substrate were prepared by sol-gel process using alkoxide solutions containing perfluoroalkylsilane (PFAS) and tetraethoxysilane (TEOS). The physical properties of the coating films were characterized by SEM, FT-IR, and XRD. And their surface properties were investigated by measuring contact angles and atomic compositions. Transparent coating films with smooth surface and uniform thickness could be obtained. The contact angles of the coating films for water and methylene iodide are extremely high, at 118 degrees and 97 degrees, respectively, and their surface free energies are about 9.7 dyn/cm. It was found that the water-repellent glass prepared is very hydrophobic and exhibits excellent water-repellency. Hydrophobic perfluoroalkyl groups are preferentially enriched to the outermost layer at the coating film-air interface, and two layers probably exist in the coating film. The upper layer oriented toward the air is composed of mainly perfluoroalkyl groups originating from PFAS, and the lower layer is composed of mainly -OSiO- groups originating from TEOS. The heat treatment after drying step cannot influence the surface enrichment of the perfluoroalkyl group. The hydrolysis reaction should be more completely done before the dip coating step to obtain lower surface free energy. The burning temperature should be less than 300 degrees C because the perfluoroalkyl group begins to decompose from this temperature. Copyright 2001 Academic Press. PMID:11237451

  13. 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.

  14. A silica sol-gel design strategy for nanostructured metallic materials

    Science.gov (United States)

    Warren, Scott C.; Perkins, Matthew R.; Adams, Ashley M.; Kamperman, Marleen; Burns, Andrew A.; Arora, Hitesh; Herz, Erik; Suteewong, Teeraporn; Sai, Hiroaki; Li, Zihui; Werner, Jörg; Song, Juho; Werner-Zwanziger, Ulrike; Zwanziger, Josef W.; Grätzel, Michael; Disalvo, Francis J.; Wiesner, Ulrich

    2012-05-01

    Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals—including noble metals—to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm-1. This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

  15. Substrate effect on nanoporous structure of silica wires by channel-confined self-assembly of block-copolymer and sol-gel precursors

    Directory of Open Access Journals (Sweden)

    Michael Z. Hu

    2015-09-01

    Full Text Available Nanoporous silica wires of various wire diameters were developed by space-confined molecular self-assembly of triblock copolymer ethylene/propylene/ethylene (P123 and silica alkoxide precursor (tetraethylorthosilicate, TEOS. Two distinctive hard-templating substrates, anodized aluminum oxide (AAO and track-etched polycarbonate (EPC, with channel diameters in the range between 10 nm and 200 nm were employed for space-confinement of soft molecular self-assembly driven by the block-copolymer microphase separation. It was observed in the scanning and transmission electron microscope (STEM studies that the substrate geometry and material characteristics had pronounced effects on the structure and morphology of the silica nanowires. A “substrate wall effect” was proposed to explain the ordering and orientation of the intra-wire mesostructure. Circular and spiral nanostructures were found only in wires formed in AAO substrate, not in EPC. Pore-size differences and distinctive wall morphologies of the nanowires relating to the substrates were discussed. It was shown that the material and channel wall characteristics of different substrates play key roles in the ordering and morphology of the intra-wire nanostructures.

  16. Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y2O3 passivation

    International Nuclear Information System (INIS)

    We demonstrate back channel improvement of back-channel-etch amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors by using solution-processed yttrium oxide (Y2O3) passivation. Two different solvents, which are acetonitrile (35%) + ethylene glycol (65%), solvent A and deionized water, solvent B are investigated for the spin-on process of the Y2O3 passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO3-based wet-etch process. Both solvents yield devices with good performance but those passivated by using solvent B exhibit better light and bias stability. Presence of yttrium at the a-IGZO back interface, where it occupies metal vacancy sites, is confirmed by X-ray photoelectron spectroscopy. The passivation effect of yttrium is more significant when solvent A is used because of the existence of more metal vacancies, given that the alcohol (65% ethylene glycol) in solvent A may dissolve the metal oxide (a-IGZO) through the formation of alkoxides and water

  17. 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.

  18. Elaboration of tin oxide nano-islands through post-deposition thermal treatment

    International Nuclear Information System (INIS)

    Tin dioxide (SnO2) films have been grown onto (006) sapphire substrates by sol–gel dip-coating using tin alkoxide solutions. It is shown, using transmission electron microscopy and atomic force microscopy, that the thickness of the layers is easily controlled with tin concentration. It can vary after the deposition process between few nanometers and few tens of nanometers according to the concentration of the precursor in the sol. A post-deposition thermal treatment forces the continuous precursor film to split into isolated islands. A decrease of the tin concentration in the precursor sol to 100 μM allows the formation of islands of a few nanometers (3 nm) in height and several tens of nanometers in diameter (30 nm). Such height value is very close to the Bohr radius of SnO2. - Highlights: • SnO2 films have been grown onto sapphire by sol–gel dip-coating. • The thickness of the layers is easily controlled with tin concentration. • The continuous precursor film splits into isolated islands after a thermal treatment. • SnO2 nano-islands of 3 nm have been synthesized by decreasing the tin concentration. • SnO2 nano-islands with such characteristics could be used for optical applications

  19. 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.

  20. Cathodoluminescence of Ce-doped Gd2SiO5 and Gd9.33(SiO4)6O2 phosphor under continuous electron irradiation

    International Nuclear Information System (INIS)

    Research highlights: → GSO:Ce is stable under continuous electron irradiation. → GSO:Ce has high luminescence efficiency. → GSO:Ce has rigid crystal structure. - Abstract: Cathodoluminescence was studied on well crystallized Ce-doped Gd2SiO5 (GSO:Ce) and Gd9.33(SiO4)6O2 (GSAP:Ce) prepared by calcining the hydrolyzed alkoxides at 1573 K because GSO:Ce is easily contaminated with GSAP:Ce impurity in solid state reaction. The luminescence efficiency of GSO:Ce was much higher than that of GSAP:Ce, and Stokes shift of the former was smaller than that of the latter, due to the crystal structural difference between the compounds in Gd2O3 and SiO2 binary chemical composition. The luminescence of GSO:Ce degraded much less than that of GSAP:Ce under the continuous electron irradiation (CL degradation). The CL degradation was related to the formation of the carbon overlayer on the phosphor particles from the vacuum ambient during the irradiation in the present manuscript. The amount of the deposited carbon was influenced by the luminescence efficiency.

  1. 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)

  2. Methods for and products of processing nanostructure nitride, carbonitride and oxycarbonitride electrode power materials by utilizing sol gel technology for supercapacitor applications

    Science.gov (United States)

    Huang, Yuhong; Wei, Oiang; Chu, Chung-tse; Zheng, Haixing

    2001-01-01

    Metal nitride, carbonitride, and oxycarbonitride powder with high surface area (up to 150 m.sup.2 /g) is prepared by using sol-gel process. The metal organic precursor, alkoxides or amides, is synthesized firstly. The metal organic precursor is modified by using unhydrolyzable organic ligands or templates. A wet gel is formed then by hydrolysis and condensation process. The solvent in the wet gel is then be removed supercritically to form porous amorphous hydroxide. This porous hydroxide materials is sintered to 725.degree. C. under the ammonia flow and porous nitride powder is formed. The other way to obtain high surface area nitride, carbonitride, and oxycarbonitride powder is to pyrolyze polymerized templated metal amides aerogel in an inert atmosphere. The electrochemical capacitors are prepared by using sol-gel prepared nitride, carbonitride, and oxycarbonitride powder. Two methods are used to assemble the capacitors. Electrode is formed either by pressing the mixture of nitride powder and binder to a foil, or by depositing electrode coating onto metal current collector. The binder or coating is converted into a continuous network of electrode material after thermal treatment to provide enhanced energy and power density. Liquid electrolyte is soaked into porous electrode. The electrochemical capacitor assembly further has a porous separator layer between two electrodes/electrolyte and forming a unit cell.

  3. Incorporation of anti-inflammatory agent into mesoporous silica

    Science.gov (United States)

    Rodrigues Braz, Wilson; Lamec Rocha, Natállia; de Faria, Emerson H.; Silva, Márcio L. A. e.; Ciuffi, Katia J.; Tavares, Denise C.; Furtado, Ricardo Andrade; Rocha, Lucas A.; Nassar, Eduardo J.

    2016-09-01

    The unique properties of macroporous, mesoporous, and microporous systems, including their ability to accommodate molecules of different sizes inside their pores and to act as drug delivery systems, have been the object of extensive studies. In this work, mesoporous silica with hexagonal structure was obtained by template synthesis via the sol-gel process. The resulting material was used as support to accommodate the anti-inflammatory agent indomethacin. The alkaline route was used to prepare the mesoporous silica; cetyltrimethylammonium bromide was employed as porogenic agent. The silica particles were functionalized with 3-aminopropyltriethoxysilane alkoxide (APTES) by the sol-gel post-synthesis method. Indomethacin was incorporated into the silica functionalized with APTES and into non-functionalized silica. The resulting systems were characterized by x-ray diffraction (XRD), specific area, infrared spectroscopy, and thermal analyses (TGA). XRD attested to formation of mesoporous silica with hexagonal structure. This structure remained after silica functionalization with APTES and incorporation of indomethacin. Typical infrared spectroscopy vibrations and organic material decomposition during TGA confirmed silica functionalization and drug incorporation. The specific surface area and pore volume of the functionalized material incorporated with indomethacin decreased as compared with the specific surface area and pore volume of the non-functionalized silica containing no drug, suggesting both the functionalizing agent and the drug were present in the silica. Cytotoxicity tests conducted on normal fibroblasts (GM0479A) cells attested that the silica matrix containing indomethacin was less toxic than the free drug.

  4. Bicontinuous ceramics with high surface area from block copolymer templates.

    Science.gov (United States)

    Hsueh, Han-Yu; Ho, Rong-Ming

    2012-06-01

    Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established. PMID:22530553

  5. A new sol-gel processing routine without chelating agents for preparing highly transparent solutions and nanothin films: engineering the role of chemistry to design the process

    Science.gov (United States)

    Ashiri, Rouholah

    2015-01-01

    The great sensitivity of titanium alkoxides to hydrolysis makes their sol-gel transformation very fast and thus difficult to control. A method was proposed to alleviate this drawback. Preparation of highly transparent solutions and nanothin films is another objective of the present research. Employing nanoemulsion method and optimizing the processing conditions, a clear solution of well-dispersed nanosized particles was obtained. With the proposed process BaTiO3 precursor sols and nanothin films with enhanced optical transparency towards the visible were prepared. The optimal formulation of the sol consists of acetic acid, barium acetate, 2-propanol, TTIP and deionized water with 6:1:1:1:150 M ratios, respectively. It was found that the reduction of the temperature in the initial stage of mixing of precursors controls the size of the forming species and accordingly improves the stability and transparency of the sol. The results also showed that the applied modifications and optimizations significantly downsize the particles within the sol to the nanometric scale and accordingly result in a significant improvement in the optical response of the products.

  6. 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.

  7. Novel hybrid organic-inorganic sol-gel materials based on highly efficient heterocyclic push-pull chromophores

    Science.gov (United States)

    Abbotto, Alessandro; Bozio, Renato; Brusatin, Giovanna; Facchetti, Antonio; Guglielmi, Massimo; Innocenzi, Plinio; Meneghetti, Moreno; Pagani, Giorgio A.; Signorini, Raffaella

    1999-10-01

    We report the synthesis of sol-gel materials based on highly efficient heterocycle-based push-pull chromophores showing second- and third-order nonlinear optical activity. We show the proper functionalization of the best performing chromophores and their incorporation into a hybrid organic- inorganic sol-gel matrix. Different types of functionalization of the active molecule have been considered, including hydroxyl and alkoxysilyl end-groups. The functionalization strategy responded to different criteria such as stability and synthetic availability of the final molecular precursors, their solubility, and the used synthetic approach to the sol-gel material. The synthesis of the sol-gel materials has been tuned in order to preserve molecular properties and control important factors such as final concentration of the active dye in the matrix. Both acid- and base-catalyzed sol-gel synthesis has been taken into account. 3-Glycidoxypropyltrimethoxysilane and 3- aminopropyltriethoxysilane have been used as the organically modified alkoxides to prepare the hybrid organic-inorganic matrix. Characterization of the spectroscopic properties of the sol-gel materials is presented.

  8. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    International Nuclear Information System (INIS)

    Thin films of Pt-doped CeO2 were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt0 and Pt2+ mixture with the Pt2+ to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt2+ to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt2+ was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt2+/Pt ratio

  9. A two-dimensional coordination compound as a zinc ion selective luminescent probe for biological applications.

    Science.gov (United States)

    Dhara, Koushik; Karan, Santanu; Ratha, Jagnyeswar; Roy, Partha; Chandra, Goutam; Manassero, Mario; Mallik, Biswanath; Banerjee, Pradyot

    2007-09-01

    A 2D coordination compound {[Cu2(HL)(N3)]ClO4}infinity (1; H3L = 2,6-bis(hydroxyethyliminoethyl)-4-methyl phenol) was synthesized and characterized by single-crystal X-ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]2H2O (2); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19-fold Zn2+-selective chelation-enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.

  10. Titanium complex formation of organic ligands in titania gels.

    Science.gov (United States)

    Nishikiori, Hiromasa; Todoroki, Kenta; Setiawan, Rudi Agus; Teshima, Katsuya; Fujii, Tsuneo; Satozono, Hiroshi

    2015-01-27

    Thin films of organic ligand-dispersing titania gels were prepared from titanium alkoxide sols containing ligand molecules by steam treatment without heating. The formation of the ligand-titanium complex and the photoinduced electron transfer process in the systems were investigated by photoelectrochemical measurements. The complex was formed between the 8-hydroxyquinoline (HQ) and titanium species, such as the titanium ion, on the titania nanoparticle surface through the oxygen and nitrogen atoms of the quinolate. A photocurrent was observed in the electrodes containing the complex due to the electron injection from the LUMO of the complex into the titania conduction band. A bidentate ligand, 2,3-dihydroxynaphthalene (DHN), formed the complex on the titania surface through dehydration between its two hydroxyl groups of DHN and two TiOH groups of the titania. The electron injection from the HOMO of DHN to the titania conduction band was observed during light irradiation. This direct electron injection was more effective than the two-step electron injection.

  11. Influences of acid on molecular forms of fluorescein and photoinduced electron transfer in fluorescein-dispersing sol-gel titania films.

    Science.gov (United States)

    Nishikiori, Hiromasa; Setiawan, Rudi Agus; Miyashita, Kyohei; Teshima, Katsuya; Fujii, Tsuneo

    2014-01-01

    Fluorescein-dispersing titania gel films were prepared by the acid-catalyzed sol-gel reaction using a titanium alkoxide solution containing fluorescein. The molecular forms of fluorescein in the films, depending on its acid-base equilibria, and the complex formation and photoinduced electron transfer process between the dye and titania surface were investigated by fluorescence and photoelectric measurements. The titanium species were coordinated to the carboxylate and phenolate-like groups of the fluorescein species. The quantum efficiencies of the fluorescence quenching and photoelectric conversion were higher upon excitation of the dianion species interacting with the titania, i.e. the dye-titania complex. This result indicated that the dianion form was the most favorable for formation of the dye-titania complex exhibiting the highest electron transfer efficiency. Using nitric acid as the catalyst, the titania surface bonded to the fluorescein instead of the adsorbed nitrate ion during the steam treatment. The dye-titania complex formation played an important role in the electron injection from the dye to the titania conduction band.

  12. 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.

  13. Eu(III) incorporation in sol-gel aluminum-yttrium matrix by non-hydrolytic route

    International Nuclear Information System (INIS)

    The sol-gel method using metal alkoxide has been investigated to prepare aluminum-yttrium oxide as yttrium-aluminum garnet (YAG) matrix composite fiber. In this paper we investigate the influence of yttrium content and temperature in the synthesis of Eu(III)-doped aluminum-yttrium oxide by non-hydrolytic sol-gel route. The formation process and the local structure of the samples were discussed by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. For temperatures around 800 deg. C, initial crystallization was observed and the phases Y4Al2O9 (YAM) and Y3Al5O12 (YAG) appear. For samples treated at 800 and 1500 deg. C the emission spectra display preferentially the f-f transitions characteristic of the YAM monoclinic phase, whereas the YAG cubic appears as the favored phase at 1100 deg. C, in accordance with the Eu(III) centrosymmetrical local site

  14. 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)

  15. 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.

  16. 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

    2016-09-01

    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. PMID:27528488

  17. Preparation and tribological properties of inclusion complex of β-cyclodextrin/dialkyl pentasulfide as additive in PEG-600 aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Jiju; Xu, Xuefeng, E-mail: xuxuefeng@zjut.edu.cn; Li, Gan; Peng, Wei

    2014-01-15

    The inclusion complex of β-cyclodextrin (β-CD) and dialkyl pentasulfide (DPS), in which DPS was incorporated into β-CD cavities, was prepared by a co-precipitation method. The tribological properties of the complex used as lubricant additive in PEG 600 aqueous solution were investigated by a four-ball tester. The complex exhibited better tribological properties than β-CD under different loads, and also showed better anti-friction performance than DPS in the latter half of the test duration. The tribological action mechanism of the complex on a steel surface was studied according to the X-ray photoelectron spectroscopy (XPS) analyses. The β-CD molecules of the complexes were decomposed into various molecular fragments and the DPS molecules were released under the friction condition. It revealed that thiolate and ferrous sulfide (FeS) films formed by DPS played a major role, and iron alkoxide and carbon deposition films formed by the friction fragments of β-CD mainly exhibited anti-friction property on FeS-to-FeS interface. The interactions among different films led to the formation of a mixed boundary lubrication film.

  18. Evaluating sol-gel ceramic thin films for metal implant applications: III. In vitro aging of sol-gel-derived zirconia films on Ti-6Al-4V.

    Science.gov (United States)

    Kirk, P B; Filiaggi, M J; Sodhi, R N; Pilliar, R M

    1999-01-01

    Sol-gel-derived zirconia films were deposited onto polished Ti-6Al-4V substrates by dip-coating from an alkoxide precursor solution. No change in morphology of the zirconia film was observed after aging at 37 degrees C for 4-12 weeks in pH 4.0 buffer solution or Hanks' balanced salt solution (HBSS), although a precipitate predominantly composed of calcium phosphate was formed on those films aged in HBSS. X-ray diffraction identified the phase of the zirconia film as either cubic or tetragonal, and revealed no degradation to the monoclinic phase after aging. By a substrate straining test, the fracture strain of the coating was revealed to be 1.5%, above the yield strain of the titanium alloy substrate. At this strain level, through-thickness cracks formed in the coating where slip bands emerged from the substrate. Qualitatively, the adhesion of the film was sufficient to prevent gross delamination of the film at high strain levels, although small regions of delamination were caused by compressive buckling of the film. This behavior indicates generally good adhesion. No change in this behavior was observed after aging.

  19. 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

    2012-03-01

    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.

  20. XPS structural characterization of Pd/SiO{sub 2} catalysts prepared by cogelation

    Energy Technology Data Exchange (ETDEWEB)

    Beketov, G. [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, CP243 Campus Plaine, B-1050 Bruxelles (Belgium); Heinrichs, B.; Pirard, J.-P. [Laboratoire de Génie Chimique, B6a, Université de Liège, B-4000 Liège (Belgium); Chenakin, S. [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, CP243 Campus Plaine, B-1050 Bruxelles (Belgium); Kruse, N., E-mail: nkruse@ulb.ac.be [Université Libre de Bruxelles (ULB), Chimie-Physique des Matériaux, CP243 Campus Plaine, B-1050 Bruxelles (Belgium)

    2013-12-15

    Nanostructured Pd/SiO{sub 2} xerogel catalysts prepared via cogelation were characterized by X-ray photoelectron spectroscopy. The preparation route allowed highly porous silica particles to be formed along with embedded Pd nanocrystals. After heat-treating the catalysts in vacuum, Pd was found to be in the metallic state. To obtain information on the xerogel catalyst texture and, in particular, on the size of the silica particles, a theoretical formalism was developed based on measuring the relative intensities of Pd 3d doublet and the associated background tail due to inelastically scattered photoelectrons. The suggested procedure also involved the measurement of the background tails accompanying Si 2p and O 1s spectral lines as internal standards. Using the developed formalism, the size of the silica particles in the catalysts after different treatments was evaluated and compared with TEM data. The results obtained indicate that the textural properties of the sol–gel catalysts start to develop already at the level of co-condensation of alkoxides with the network-forming reagent. Calcination causes these properties to run to completion.

  1. Biological characterization of a new silicon based coating developed for dental implants.

    Science.gov (United States)

    Martínez-Ibáñez, M; Juan-Díaz, M J; Lara-Saez, I; Coso, A; Franco, J; Gurruchaga, M; Suay Antón, J; Goñi, Isabel

    2016-04-01

    Taking into account the influence of Si in osteoblast cell proliferation, a series of sol-gel derived silicon based coating was prepared by controlling the process parameters and varying the different Si-alkoxide precursors molar rate in order to obtain materials able to release Si compounds. For this purpose, methyltrimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) were hydrolysed together and the sol obtained was used to dip-coat the different substrates. The silicon release ability of the coatings was tested finding that it was dependent on the TEOS precursor content, reaching a Si amount value around ninefolds higher for coatings with TEOS than for the pure MTMOS material. To test the effect of this released Si, the in vitro performance of developed coatings was tested with human adipose mesenchymal stem cells finding a significantly higher proliferation and mineralization on the coating with the higher TEOS content. For in vivo evaluation of the biocompatibility, coated implants were placed in the tibia of the rabbit and a histological analysis was performed. The evaluation of parameters such as the bone marrow state, the presence of giant cells and the fibrous capsule proved the biocompatibility of the developed coatings. Furthermore, coated implants seemed to produce a qualitatively higher osteoblastic activity and a higher number of bone spicules than the control (uncoated commercial SLA titanium dental implant). PMID:26936366

  2. Uranyl ion complexation by citric and citramalic acids in the presence of di-amines

    International Nuclear Information System (INIS)

    Uranyl nitrate reacts with citric (H4cit) or D-(-)-citramalic (H3citml) acids under mild hydrothermal conditions and in the presence of di-amines to give different complexes which are all characterized by the presence of 2:2 uranyl/poly-carboxylate di-anionic dimers or of polymeric chains based on the same dimeric motif. Each uranium ion is chelated by the two ligands through the alkoxide and the α- or β-carboxylate groups, the second β-carboxylic group in citrate being uncoordinated. The uranium coordination sphere is completed by either a water molecule or the β-carboxylate group of a neighboring unit, thus giving zero- or one-dimensional assemblages, respectively. The evidence for [UO2(Hcit)]2 dimers in the solid state confirms previous results from potentiometric and EXAFS measurements on solutions. Depending on the diamine used (DABCO, 2,2'- and 4,4'-bipyridine, [2.2.2]cryptand) and its ability to form divergent hydrogen bonds or not, different uranyl/poly-carboxylate topologies are obtained, thus evidencing template effects, and extended hydrogen bonding gives two- or three-dimensional assemblages. These results, together with those previously obtained with NaOH as a base, add to the knowledge of the uranyl/citrate system, which is much investigated for its environmental relevance. (author)

  3. 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.

  4. 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.

  5. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zanfoni, N.; Avril, L.; Imhoff, L.; Domenichini, B., E-mail: bruno.domenichini@u-bourgogne.fr; Bourgeois, S.

    2015-08-31

    Thin films of Pt-doped CeO{sub 2} were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt{sup 0} and Pt{sup 2+} mixture with the Pt{sup 2+} to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt{sup 2+} to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt{sup 2+} was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt{sup 2+}/Pt ratio.

  6. Assessing extreme models of the Stoeber synthesis using transients under a range of initial composition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.; McCormick, A.V. [Univ. of Minnesota, Minneapolis, MN (United States); Look, J.L. [Oak Ridge National Lab., TN (United States); Harris, M.T. [Univ. of Maryland, College Park, MD (United States). Dept. of Chemical Engineering

    1997-10-01

    Monodispersely sized micrometer-scale spherical colloids of metal oxides are important for the controlled fabrication of high quality ceramic materials. Their synthesis by the hydrolysis of metal alkoxides is of particular interest. {sup 29}Si-NMR, conductimetry, and photon correlation spectroscopy are used to monitor the temporal profile of intermediate concentrations in Stoeber synthesis (i.e., ammonia-catalyzed hydrolysis of tetraethoxysilane in a batch reactor). Extreme models of the process are assessed by examining the effect of initial composition on these transients (over a wider range of composition than attempted previously). The trends with initial composition suggest that the nucleation is rate-limited by the hydrolysis of the singly hydrolyzed monomer, the product of which probably phase separates. Moreover, the trends are consistent with the aggregation model discussed by G.H. Bogush and C.F. Zukoski (J. Colloid Interface Sci. 142, 1, 19, 1991) and by M.T. Harris (Ph.D. dissertation, Univ. of Tennessee, 1992). The trends are not consistent with a growth model without aggregation.

  7. 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.

  8. 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.

  9. Ring-opening polymerization of rac-lactide mediated by tetrametallic lithium and sodium diamino-bis(phenolate) complexes.

    Science.gov (United States)

    Alhashmialameer, Dalal; Ikpo, Nduka; Collins, Julie; Dawe, Louise N; Hattenhauer, Karen; Kerton, Francesca M

    2015-12-14

    Lithium and sodium compounds supported by tetradentate amino-bis(phenolato) ligands, [Li2(N2O2(BuBuPip))] (1), [Na2(N2O2(BuBuPip))] (2) (where [N2O2(BuBuPip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4,6-tert-butylphenol), and [Li2(N2O2(BuMePip))] (3), [Na2(N2O2(BuMePip))] (4) (where [N2O2(BuMePip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4-methyl-6-tert-butylphenol) were synthesized and characterized by NMR spectroscopy and MALDI-TOF mass spectrometry. Variable temperature NMR experiments were performed to understand solution-phase dynamics. The solid-state structures of 1 and 4 were determined by X-ray diffraction and reveal tetrametallic species. PGSE NMR spectroscopic data suggests that 1 maintains its aggregated structure in CD2Cl2. The complexes exhibit good activity for controlled ring-opening polymerization of rac-lactide (LA) both solvent free and in solution to yield PLA with low dispersities. Stoichiometric reactions suggest that the formation of PLA may proceed by the typical coordination-insertion mechanism. For example, (7)Li NMR experiments show growth of a new resonance when 1 is mixed with 1 equiv. LA and (1)H NMR data suggests formation of a Li-alkoxide species upon reaction of 1 with BnOH. PMID:26538475

  10. High Quality YBCO Film Growth on SrTiO3-Buffered LaAlO3 Substrate by Full Solution Method

    Institute of Scientific and Technical Information of China (English)

    Sansheng WANG; Lin WANG; Bingfu GU

    2008-01-01

    A full solution method has been developed as a low cost process of YBa2Cu3O7-x (YBCO) coated conductor fabrication.In this study,highly biaxially textured SrTiO3 (STO) buffer layers were fabricated on LaAlO3 (LAO) single crystal substrates by sol-gel method using metal alkoxides as the staring precursor materials.High quality YBCO superconducting film was then fabricated on STO-buffered LAO substrate by triflvoroacetic metalorganic deposition (TFA-MOD) method.For the YBCO superconducting film,only (001) diffraction peaks can be detected by XRD (X-ray diffraction) analysis with no other phases detectable.Especially,In-plane texture of YBCO film is improved compared to that of STO buffer layer from phi scans analysis,which indicates the self-epitaxy phenomenon explained by considering interfacial energy.STO and YBCO films both show c-axis oriented grains growt.h and have uniform surface microstructure.A critical transition temperature,Tc (R=0) of 89.5 K and a critical current density of 2 mA/cm2 (17 K,self-field) were obtained for a 0.2 μm thick YBCO film on STO-buffered LAO substrate.No reaction between YBCO and STO was detected by XRD analysis.This full solution process may provide a promising low cost fabrication route for YBCO coated conductors on metal tape.

  11. Thermal chemistry of the Cu-KI5 atomic layer deposition precursor on a copper surface

    International Nuclear Information System (INIS)

    The thermal chemistry of a Cu(I) ketoiminate complex, Cu-KI5, resulting from the modification of the known Air Products CupraSelect® copper CVD precursor Cu(hfac)(tmvs) designed to tether the two ligands via an isopropoxide linker, was studied under ultrahigh vacuum on a Cu(110) single-crystal surface by using a combination of temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy. Adsorption at low temperatures was determined to take place via the displacement of the vinyl ligand by the surface. Molecular desorption was seen at 210 K, and the evolution of Cu(II)-KI52 was established to take place at 280 K, presumably from a disproportionation reaction that also leads to the deposition of Cu(0). Other sets of desorption products were seen at 150, 250, and 430 K, all containing copper atoms and small organic moieties with molecular masses below 100 amu. The latter TPD peak in particular indicates significant fragmentation of the ligands, likely at the C–N bond that holds the vinylsilane-isopropoxide moiety tethered to the ketoimine fragment, and possibly also at the union between the vinylsilane and the alkoxide linker. The 430 K temperature measured for this chemistry may set an upper limit for clean Cu film deposition, but since reactivity on the surface was also found to be inhibited at higher surface coverages, it may be delayed to higher temperatures under atomic layer deposition conditions

  12. Fabrication of highly crystalline oxide thin films on plastics: Sol–gel transfer technique involving high temperature process

    Directory of Open Access Journals (Sweden)

    Hiromitsu Kozuka

    2016-09-01

    Full Text Available Si(100 substrates were coated with a polyimide (PI–polyvinylpyrrolidone (PVP mixture film, and an alkoxide-derived TiO2 gel film was deposited on it by spin-coating. The gel films were fired under various conditions with final annealing at 600–1000 °C. The PI–PVP layer was completely decomposed at such high temperatures while the TiO2 films survived on Si(100 substrates without any damages. When the final annealing temperature was raised, the crystalline phase changed from anatase to rutile, and the crystallite size and the refractive index of the films tended to increase. The TiO2 films thus fired on Si(100 substrates were transferred to polycarbonate (PC substrates by melting the surface of the plastic substrate either in a near-infrared image furnace or on a hot plate under a load. Cycles of deposition and firing were found to be effective in achieving successful transfer even for the films finally annealed at 1000 °C. X-ray photoelectron spectroscopic analyses on the film/Si(100 interface suggested that the residual carbon or carbides at the interface could be a possible factor, but not a necessary and decisive factor that allows the film transfer.

  13. Part 1. Approaches to the total synthesis of the diterpene marrubin. Part II. Ligand assisted nucleophilic additions. Part III. Coal processing in a non-dissolving medium

    Energy Technology Data Exchange (ETDEWEB)

    Lipscombe, J.; Charles, W. II

    1987-01-01

    The total synthesis of the diterpene marrubiin was attempted using methodology previously developed in the Liotta laboratories. Ligand Assisted Nucleophilic Additions (LANA) comprise a new class of synthetic reactions involving the stereoselective addition of some group, usually in an intramolecular conjugate fashion. This group is itself derived from an earlier nucleophilic addition to a carbonyl moiety. Exchange of the original metal of the alkoxide with a second metal (which must be at least divalent) having a transferrable group demands that the stereochemistry of the first addition control the second. The general features of these types of processes are discussed. Initial work with substituted quinones is presented, and some mechanistic rationales are given. A novel method of coal processing at modest temperatures and hydrogen pressures (250-300/sup 0/C, 8.0 MPa) is discussed. Coals reacted with small amounts of tetrahydroquinoline in the presence of fluorocarbons or other non-dissolving media underwent astounding increases in pyridine solubility, a common standard in coal liquefaction studies. Several additives were employed, although only tetrahydroquinoline was found to effectively increase coal solubility. Coals having vastly different individual properties behaved similarly under these conditions. Kinetic and model studies were used in an attempt to clarify the reactions occurring under these novel conditions.

  14. 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)

  15. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. 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.

  18. One-Step Synthesis of TiO2/Perlite Composites by Flame Spray Pyrolysis and Their Photocatalytic Behavior

    Directory of Open Access Journals (Sweden)

    M. Giannouri

    2013-01-01

    Full Text Available TiO2/perlite composites were prepared via facile one-step flame spray pyrolysis (FSP route. Titanium alkoxide (TIPO and expanded perlite were used as Ti source and substrate, respectively. Precursor TIPO-ethanol solutions containing homogeneously dispersed perlite particles were processed through FSP setup at different experimental conditions regarding the gas flow and precursor supply rates. The structure, morphology, and the composition of the obtained powders were investigated. The porosity and the light absorbance of the TiO2/perlite composites were examined and their photocatalytic activity in NO oxidation was evaluated. Commercial titania powder P25 was also FSP processed and investigated for comparison. The XRD analysis revealed that biphased titania with different anatase-rutile ratio and particles size 20–40 nm was synthesized onto the perlite which according to microscopy results was covered by neck-connected TiO2 nanoparticles. The anatase-rutile interplay was also demonstrated by the Raman spectra where presence of Si-O-Ti vibrational modes was observed for some samples. The UV-Vis diffuse reflectance spectra of the TiO2/perlite composites revealed up to 70% reflection that was connected to the presence of the gray perlite and superficial carbon. The best photocatalytic activity of the composites was connected to almost equal anatase-rutile ratio and possible synergetic effect of the two TiO2 phases.

  19. Ethylene glycol-assisted coating of titania on nanoparticles.

    Science.gov (United States)

    Dahl, Michael; Castaneda, Fernando; Joo, Ji Bong; Reyes, Victor; Goebl, James; Yin, Yadong

    2016-06-14

    Coating titania shells onto sub-micron sized particles has been widely studied recently, with success mainly limited to objects with sizes above 50 nm. Direct coating on particles below this size has been difficult to attain especially with good control over properties such as thickness and crystallinity. Here we demonstrate that titanium-glycolate formed by reacting titanium alkoxide and ethylene glycol is an excellent precursor for coating titania on aqueous nanoparticles. The new coating method is particularly useful for its ability to coat materials lacking strong polymers or ligands which are frequently needed to facilitate typical titania coatings. We demonstrate the effectiveness of the process of coating titania on metal nanoparticles ranging from citrate-stabilized gold and silver spheres to gold nanorods and silver nanoplates, and larger particles such as SiO2 microspheres and polymer spheres. Further the thickness of these coatings can be tuned from a few nanometers to ∼40 nm through sequential coatings. These coatings can subsequently be crystallized into TiO2 through refluxing in water or by calcination to obtain crystalline shells. This procedure can be very useful for the production of TiO2 coatings with tunable thickness and crystallinity as well as for further study on the effect of TiO2 coatings on nanoparticles.

  20. Synthesis of amorphous zirconium oxide with luminescent characteristics

    International Nuclear Information System (INIS)

    It was prepared zirconium oxide, ZrO2, by means of hydrolysis-condensation reactions (sol-gel method), using zirconium propoxide, Zr(C3H7O)4, as precursor and nitric acid, HNO3, as catalyst of the hydrolysis reaction. In this synthesis it was used a molar ratio water-alkoxide, r=nH2O/nZr(C3H70)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 ZrO2 obtained by this way is amorphous even to 300 C and it consists of big aggregates. The amorphous ZrO2, presents thermoluminescent behavior, after it was irradiated with UV radiation and beta particles of 90Sr/90Y and it was thermally stimulated. (Author)

  1. Surface derivatization strategy for combinatorial analysis of cell response to mixtures of protein domains.

    Science.gov (United States)

    Chiang, Chunyi; Karuri, Stella W; Kshatriya, Pradnya P; Schwartz, Jeffrey; Schwarzbauer, Jean E; Karuri, Nancy W

    2012-01-10

    We report a robust strategy for conjugating mixtures of two or more protein domains to nonfouling polyurethane surfaces. In our strategy, the carbamate groups of polyurethane are reacted with zirconium alkoxide from the vapor phase to give a surface-bound oxide that serves as a chemical layer that can be used to bond organics to the polymer substrate. A hydroxyalkylphosphonate monolayer was synthesized on this layer, which was then used to covalently bind primary amine groups in protein domains using chloroformate-derived cross-linking. The effectiveness of this synthesis strategy was gauged by using an ELISA to measure competitive, covalent bonding of cell-binding (III(9-10)) and fibronectin-binding (III(1-2)) domains of the cell adhesion protein fibronectin. Cell adhesion, spreading, and fibronectin matrix assembly were examined on surfaces conjugated with single domains, a 1:1 surface mixture of III(1-2) and III(9-10), and a recombinant protein "duplex" containing both domains in one fusion protein. The mixture performed as well as or better than the other surfaces in these assays. Our surface activation strategy is amenable to a wide range of polymer substrates and free amino group-containing protein fragments. As such, this technique may be used to create biologically specific materials through the immobilization of specific protein groups or mixtures thereof on a substrate surface.

  2. High rate capability of a BaTiO3-decorated LiCoO2 cathode prepared via metal organic decomposition

    Science.gov (United States)

    Teranishi, Takashi; Katsuji, Naoto; Yoshikawa, Yumi; Yoneda, Mika; Hayashi, Hidetaka; Kishimoto, Akira; Yoda, Koji; Motobayashi, Hidefumi; Tasaki, Yuzo

    2016-10-01

    Metal organic decomposition (MOD) using octylic acid salts was applied to synthesize a BaTiO3-LiCoO2 (BT-LC) composite powder. The Ba and Ti octylates were utilized as metal precursors, in an attempt to synthesize homogeneous BT nanoparticles on the LC matrix. The BT-LC composite, having a phase-separated composite structure without any impurity phase, was successfully obtained by optimizing the MOD procedure. The composite prepared using octylate precursors exhibited a sharper distribution and better dispersibility of decorated BT particles. Additionally, the average particle size of the decorated BTs using metal octylate was reduced to 23.3 nm, compared to 44.4 nm from conventional processes using Ba acetate as well as Ti alkoxide as precursors. The composite cathode displayed better cell performance than its conventional counterpart; the discharge capacity of the metal octylate-derived specimen was 55.6 mAh/g at a 50C rate, corresponding to 173% of the capacity of the conventional specimen (32.2 mAh/g). The notable improvement in high rate capability obtained in this study, compared with the conventional route, was attributed to the higher density of the triple junction formed by the BT-LC-electrolyte interface.

  3. Synthesis of nano titania particles embedded in mesoporous SBA-15: Characterization and photocatalytic activity

    International Nuclear Information System (INIS)

    Supported nanocrystalline titanium dioxide (TiO2) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO2/SBA-15 composites with various TiO2 loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO2 did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 deg. C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO2 grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO2/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO2 nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites

  4. Biological characterization of a new silicon based coating developed for dental implants.

    Science.gov (United States)

    Martínez-Ibáñez, M; Juan-Díaz, M J; Lara-Saez, I; Coso, A; Franco, J; Gurruchaga, M; Suay Antón, J; Goñi, Isabel

    2016-04-01

    Taking into account the influence of Si in osteoblast cell proliferation, a series of sol-gel derived silicon based coating was prepared by controlling the process parameters and varying the different Si-alkoxide precursors molar rate in order to obtain materials able to release Si compounds. For this purpose, methyltrimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) were hydrolysed together and the sol obtained was used to dip-coat the different substrates. The silicon release ability of the coatings was tested finding that it was dependent on the TEOS precursor content, reaching a Si amount value around ninefolds higher for coatings with TEOS than for the pure MTMOS material. To test the effect of this released Si, the in vitro performance of developed coatings was tested with human adipose mesenchymal stem cells finding a significantly higher proliferation and mineralization on the coating with the higher TEOS content. For in vivo evaluation of the biocompatibility, coated implants were placed in the tibia of the rabbit and a histological analysis was performed. The evaluation of parameters such as the bone marrow state, the presence of giant cells and the fibrous capsule proved the biocompatibility of the developed coatings. Furthermore, coated implants seemed to produce a qualitatively higher osteoblastic activity and a higher number of bone spicules than the control (uncoated commercial SLA titanium dental implant).

  5. Synthesis, crystal structure of diferrous complex and its reactivity with dioxygen

    Institute of Scientific and Technical Information of China (English)

    阎世平; 程鹏; 王庆伦; 廖代正; 姜宗慧; 王耕霖

    2000-01-01

    The dinuclear complex of [Fe2L{O2P(OPh)2}](CIO4)2 ·Et2O(1) (where L represents the dinucleating ligand N-Et-HPTB, anion of N, N, N’, N’-tetrakis (N-ethyl-2-benzimidazolyemethyl)-2-hydroxy-1, 3-diamino-propane) has been synthesized and crystallizes in the triclinic space group P T with cell constants α = 1.526(3) nm, b = 1.259 8(3) nm, c = 1.563 0(3) nm , α = 94.41 (3)°, P = 115.31(3)°, β=99.90(3)°, V= 3.267(1) nm3, z=2, R = 0.084 7 and Rw = 0.177 8. The Fe(Ⅱ) sites are bridged by an alkoxide of the dinucleating ligand and a phosphate, affording a diiron core with an Fe-μ-O-Fe angle of 131.20(3)° and an Fe-Fe distance of 0.364 9 nm. Both Fe(II) centers have trigonal bipyramidal geometry. Dioxygen adduct (1/O2) forms upon exposure of the diferrous complex to O2 at low temperature (-60℃). The 1/O2 adduct is stable at -60℃ but decomposes upon warming. The adduct exhibits visible absorption maximum near 606 nm and resonance Raman features at 478 cm-1 (γFe-o) and 897 cm-1 (γo-o), and the latter

  6. Reaction Mechanism of Pentene Skeletal Isomerization on Zeolites%分子筛催化的戊烯骨架异构反应机理

    Institute of Scientific and Technical Information of China (English)

    郭玉华; 蒲敏; 陈标华

    2011-01-01

    The microcosmic interaction mechanism of pentene skeletal isomerization on zeolites was studied by the density functional theory at the B3LYP/6-31G (d, p) level.The reaction trajectories were determined by the intrinsic reaction coordinate (IRC) methods.The results indicate that the skeletal isomerization of pentene can proceed by two kinds of mechanisms: the alkoxide intermediate mechanism and methyleyclopropane-like intermediate mechanism.The alkoxide intermediate mechanism involves two reaction pathways: methyl shift and ethyl shift.Accordingly, the overall skeletal isomerization of pentene has three reaction pathways.Both the methyl and ethyl shift mechanisms consist of three elementary steps.The rate determining steps are the shift of the methyl group and the shift of the ethyl group, respectively.The corresponding activation barriers are nearly equivalent (206.17 and 207.31 kJ·mol-1, respectively), indicating that two reaction pathways compete between each other.The methylcyclopropane-like intermediate mechanism includes two elementary steps: the torsion of the carbon chain and the methyl shift.This intermediate has highly ionic character and is a high energy species.The rate determining step is the torsion of the carbon chain, and its activation barrier is 147.93 kJ·mol-1.This value obviously is lower than those of the methyl and ethyl shift process, implying that the methylcyclopropanelike intermediate pathway occurs more easily.%在密度泛函理论中的B3LYP/6-31G(d,p)水平上研究了分子筛催化戊烯骨架异构的微观作用机制,分别对各个基元反应进行了内禀反应坐标(IRC)解析.结果表明:戊烯的骨架异构存在2种反应机理:烷氧基中间体机理和类甲基环丙烷中间体机理.而烷氧基中间体机理又包括2个反应途径,1个是甲基迁移,另1个是乙基迁移.因此,整个异构反应存在3个反应途径.甲基迁移机理和乙基迁移机理都含有3个基元步骤,其中速控步骤分别

  7. SYNTHESIS AND CHARACTERISATION OF β-DIKETONES%β-二酮类萃取剂的合成及性能研究

    Institute of Scientific and Technical Information of China (English)

    林辉

    2001-01-01

    A process for the preparation of β-diketones,especialy aromatic β-diketones,by Claisen condensation reaction of acetophenone or its derivatives with alphatic esters in the presense of sodium alkoxide as a catalyst in an aromatic hydrocarbon solvent is reported.The different β-diketones can be obtained with high yields and purity.The crude materials was commercially available.The process is facile and can permit efficient recirculation of solvent.   The experiments on testing the extraction properties of β-diketones are performed.The results indicate that these β-diketones can extract copper efficiently under certain condition and be potential to become extractant of copper.%阐述了在醇钠作催化剂、芳香烃作溶剂的条件下,由苯乙酮或其衍生物与羧酸酯发生Claisen缩合反应合成β-二酮,特别是芳香族β-二酮的方法。该合成方法的优点是可以制备出高纯度不同结构的β-二酮,且产率高;所需原料为国内易得工业品,反应溶剂可重复使用;方法简便,有较好的工业应用价值。β-二酮的萃取性能表明,它是有效的铜萃取剂。

  8. 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.

  9. Growth of epitaxial films of sodium potassium tantalate and niobate on single-crystal lanthanum aluminate [100] substrates

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, George H. [University of Tennessee, Knoxville (UTK); Specht, Eliot D [ORNL; Larese, John Z [ORNL; Xue, Ziling [University of Tennessee, Knoxville (UTK); Beach, David B [ORNL

    2008-01-01

    Epitaxial films of sodium potassium tantalate (Na{sub 0.5}K{sub 0.5}TaO{sub 3}, NKT) and sodium potassium niobate (Na{sub 0.5}K{sub 0.5}NbO{sub 3}, NKN) were grown on single-crystal lanthanum aluminate (LAO) (100) (indexed as a pseudo-cubic unit cell) substrates via an all-alkoxide solution (methoxyethoxide complexes in 2-methoxyethanol) deposition route for the first time. X-ray diffraction studies indicated that the onset of crystallization in powders formed from hydrolyzed gel samples was 550 C. {sup 13}C nuclear magnetic resonance studies of solutions of methoxyethoxide complexes indicated that mixed-metal species were formed, consistent with the low crystallization temperatures observed. Thermal gravimetric analysis with simultaneous mass spectrometry showed the facile loss of the ligand (methoxyethoxide) at temperatures below 400 C. Crystalline films were obtained at temperatures as low as 650 C when annealed in air. {theta}-2{theta} x-ray diffraction patterns revealed that the films possessed c-axis alignment in that only (h00) reflections were observed. Pole-figures about the NKT or NKN (220) reflection indicated a single in-plane, cube-on-cube epitaxy. The quality of the films was estimated via {omega} (out-of-plane) and {psi} (in-plane) scans and full-widths at half-maximum (FWHMs) were found to be reasonably narrow ({approx}1{sup o}), considering the lattice mismatch between the films and the substrate.

  10. 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.

  11. Preparation and characterization of bio-diesels from various bio-oils.

    Science.gov (United States)

    Lang, X; Dalai, A K; Bakhshi, N N; Reaney, M J; Hertz, P B

    2001-10-01

    Methyl, ethyl, 2-propyl and butyl esters were prepared from canola and linseed oils through transesterification using KOH and/ or sodium alkoxides as catalysts. In addition, methyl and ethyl esters were prepared from rapeseed and sunflower oils using the same catalysts. Chemical composition of the esters was determined by HPLC for the class of lipids and by GC for fatty acid compositions. The bio-diesel esters were characterized for their physical and fuel properties including density, viscosity, iodine value, acid value, cloud point, pure point, gross heat of combustion and volatility. Methyl and ethyl esters prepared from a particular vegetable oil had similar viscosities, cloud points and pour points, whereas methyl, ethyl, 2-propyl and butyl esters derived from a particular vegetable oil had similar gross heating values. However, their densities, which were 2 7% higher than those of diesel fuels, statistically decreased in the order of methyl approximately 2-propyl > ethyl > butyl esters. Butyl esters showed reduced cloud points (-6 degrees C to -10 degrees C) and pour points (-13 degrees C to -16 degrees C) similar to those of summer diesel fuel having cloud and pour points of -8 degrees C and -15 degrees C, respectively. The viscosities of bio-diesels (3.3-7.6 x 10(-4) Pa s at 40 degrees C) were much less than those of pure oils (22.4-45.1 x 10(-4) Pa s at 40 degrees C) and were twice those of summer and winter diesel fuels (3.50 and 1.72 x 10(-4) Pa s at 40 degrees C), and their gross heat contents of approximately 40 MJ/kg were 11% less than those of diesel fuels (approximately 45 MJ/kg). For different esters from the same vegetable oil, methyl esters were the most volatile, and the volatility decreased as the alkyl group grew bulkier. However, the bio-diesels were considerably less volatile than the conventional diesel fuels. PMID:11554602

  12. Synthesis, Characterization, and Reactivity of Amine Bis(phenolato) Cyclopentadienyl Lanthanide Complexes

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    (C5H5)3Ln(THF) reacted with amine bis(phenol) LH2[L=Me2NCH2CH2N{CH2-(2-O-C6H2-But-3-Me-5)}2] in a 1:1 molar ratio in THF to generate the amine bis(phenolato) cyclopentadienyl lanthanide complexes LLn(C5H5)(THF)·(THF)n (Ln=La (1), n=0; Ln=Sm(2), n=1) in high yields. Complexes 1 and 2 were fully characterized by elemental analysis, NMR (for 1) and IR spectra, and X-ray structural determination. The crystal data of complex 1 are monoclinic, P21/c space group, a=1.1595(1) nm, b=1.8588(2) nm, c=1.6647(1) nm, β= 98.490(2)°, V=3.5486(5) nm3, Z=4, Dc=1.338 mg·m-3, μ=1.240 mm-1, F(000)=1488, R=0.0249, wR=0.0568. The crystal data of complex 2 are monoclinic, P21/c space group, a=0.9692(1) nm, b=1.4583(2) nm, c=2.8192(3) nm, β=96.805(2)°, V=3.9584(7) nm3, Z=4, Dc=1.340 mg·m-3, μ=1.524 mm-1, F(000)=1668, R=0.0346, wR=0.0756. The attempts failed to synthesize the amine bis(phenolate) lanthanide alkoxides by the reactions of complexes 1 and 2 with alcohols. The preliminary results revealed that complex 1 can initiate ε-caprolactone polymerization.

  13. Three-coordinate beryllium β-diketiminates: synthesis and reduction chemistry.

    Science.gov (United States)

    Arrowsmith, Merle; Hill, Michael S; Kociok-Köhn, Gabriele; MacDougall, Dugald J; Mahon, Mary F; Mallov, Ian

    2012-12-17

    A series of mononuclear, heteroleptic beryllium complexes supported by the monoanionic β-diketiminate ligand [HC{CMeNDipp}(2)](-) (L; Dipp = 2,6-diisopropylphenyl) have been synthesized. Halide complexes of the form [LBeX] (X = Cl, I) and a bis(trimethylsilyl)amide complex were produced via salt metathesis routes. Alkylberyllium β-diketiminate complexes of the form [LBeR] (R = Me, (n)Bu) were obtained by salt metathesis from the chloride precursor [LBeCl]. Controlled hydrolysis of [LBeMe] afforded an air-stable, monomeric β-diketiminatoberyllium hydroxide complex. [LBeMe] also underwent facile protonolysis with alcohols to form the corresponding β-diketiminatoberyllium alkoxides [LBeOR] (R = Me, (t)Bu, Ph). High temperatures and prolonged reaction times were required for protonolysis of [LBeMe] with primary amines to yield the β-diketiminatoberyllium amide complexes [LBeNHR] (R = (n)Bu, CH(2)Ph, Ph). No reactions were observed between [LBeMe] and silanes, terminal acetylenes, or secondary amines. All compounds were characterized by (1)H, (13)C, and (9)Be NMR spectroscopy and, in most cases, by X-ray crystallography. Reduction of the beryllium chloride complex with potassium metal resulted in apparent hydrogen-atom transfer between two β-diketiminate backbones, yielding two dimeric, potassium chloride bridged diamidoberyllium species. X-ray analysis of a cocrystallized mixture of the 18-crown-6 adducts of these species allowed unambiguous identification of the two reduced diketiminate ligands, one of which had been deprotonated at a backbone methyl substituent and the other reduced by hydride addition to the β-imine position. It is proposed that this process occurs by the formation of an unobserved radical anion species and intermolecular hydrogen-atom transfer by a radical-based hydrogen abstraction mechanism. PMID:23215345

  14. Yttrium deposition on mesoporous TiO2: textural design and UV decolourization of organic dyes

    Indian Academy of Sciences (India)

    M L Ojeda; C Velasquez; V Renteria; A Campero; M A García-Sánchez; F Rojas

    2015-02-01

    This study discusses about the photochemical, topological and textural properties of yttrium-doped titanium dioxide (TiO2) photocatalysts. The mesoporous yttrium-doped TiO2 substrates prepared in this research work operate efficiently via low-cost commercial 13-W UV lamps. A quantity of 2 wt% yttrium deposition on TiO2 accelerates methyl orange UV decolourization kinetics. When Y content increases to 8 wt%, besides anatase, rutile is formed from 600°C. The Y2Ti2O7 photoinactive compound emerges at 800°C. The P-123 surfactant mesopore templating treatment of TiO2 xerogels (when concurrent with the sol–gel Y-doping of Ti alkoxides) features the following two correlated phenomena: (i) The surface area increases while the access to the inner porosity of the substrate becomes much easier, so that a larger portion of the surface is made accessible to the dye molecules as well as to the yttrium dopant; (ii) the inclusion of tubular instead of ink-bottle pores facilitates the transport of organic species in and out of the pore structure. The most active mesoporous substrate resulted to be made of 2 wt% Y; contrastingly, when Y= 8 wt%, photoinactivity arose because of Y2Ti2O7 formation. The involvement of P123 was not the sole factor influencing the efficiency of TiO2 mesoporous photocatalysts. There were additional key factors, such as the surging of co-ordination and nucleophilic species, during the dye photodegradation process, which were also induced by the presence of Y species on the surface of these substrates.

  15. Three-coordinate beryllium β-diketiminates: synthesis and reduction chemistry.

    Science.gov (United States)

    Arrowsmith, Merle; Hill, Michael S; Kociok-Köhn, Gabriele; MacDougall, Dugald J; Mahon, Mary F; Mallov, Ian

    2012-12-17

    A series of mononuclear, heteroleptic beryllium complexes supported by the monoanionic β-diketiminate ligand [HC{CMeNDipp}(2)](-) (L; Dipp = 2,6-diisopropylphenyl) have been synthesized. Halide complexes of the form [LBeX] (X = Cl, I) and a bis(trimethylsilyl)amide complex were produced via salt metathesis routes. Alkylberyllium β-diketiminate complexes of the form [LBeR] (R = Me, (n)Bu) were obtained by salt metathesis from the chloride precursor [LBeCl]. Controlled hydrolysis of [LBeMe] afforded an air-stable, monomeric β-diketiminatoberyllium hydroxide complex. [LBeMe] also underwent facile protonolysis with alcohols to form the corresponding β-diketiminatoberyllium alkoxides [LBeOR] (R = Me, (t)Bu, Ph). High temperatures and prolonged reaction times were required for protonolysis of [LBeMe] with primary amines to yield the β-diketiminatoberyllium amide complexes [LBeNHR] (R = (n)Bu, CH(2)Ph, Ph). No reactions were observed between [LBeMe] and silanes, terminal acetylenes, or secondary amines. All compounds were characterized by (1)H, (13)C, and (9)Be NMR spectroscopy and, in most cases, by X-ray crystallography. Reduction of the beryllium chloride complex with potassium metal resulted in apparent hydrogen-atom transfer between two β-diketiminate backbones, yielding two dimeric, potassium chloride bridged diamidoberyllium species. X-ray analysis of a cocrystallized mixture of the 18-crown-6 adducts of these species allowed unambiguous identification of the two reduced diketiminate ligands, one of which had been deprotonated at a backbone methyl substituent and the other reduced by hydride addition to the β-imine position. It is proposed that this process occurs by the formation of an unobserved radical anion species and intermolecular hydrogen-atom transfer by a radical-based hydrogen abstraction mechanism.

  16. 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).

  17. Polymorphic phase transition among the titania crystal structures using a solution-based approach: from precursor chemistry to nucleation process

    Science.gov (United States)

    Kumar, S. Girish; Rao, K. S. R. Koteswara

    2014-09-01

    Nanocrystalline titania are a robust candidate for various functional applications owing to its non-toxicity, cheap availability, ease of preparation and exceptional photochemical as well as thermal stability. The uniqueness in each lattice structure of titania leads to multifaceted physico-chemical and opto-electronic properties, which yield different functionalities and thus influence their performances in various green energy applications. The high temperature treatment for crystallizing titania triggers inevitable particle growth and the destruction of delicate nanostructural features. Thus, the preparation of crystalline titania with tunable phase/particle size/morphology at low to moderate temperatures using a solution-based approach has paved the way for further exciting areas of research. In this focused review, titania synthesis from hydrothermal/solvothermal method, conventional sol-gel method and sol-gel-assisted method via ultrasonication, photoillumination and ILs, thermolysis and microemulsion routes are discussed. These wet chemical methods have broader visibility, since multiple reaction parameters, such as precursor chemistry, surfactants, chelating agents, solvents, mineralizer, pH of the solution, aging time, reaction temperature/time, inorganic electrolytes, can be easily manipulated to tune the final physical structure. This review sheds light on the stabilization/phase transformation pathways of titania polymorphs like anatase, rutile, brookite and TiO2(B) under a variety of reaction conditions. The driving force for crystallization arising from complex species in solution coupled with pH of the solution and ion species facilitating the orientation of octahedral resulting in a crystalline phase are reviewed in detail. In addition to titanium halide/alkoxide, the nucleation of titania from other precursors like peroxo and layered titanates are also discussed. The non-aqueous route and ball milling-induced titania transformation is briefly

  18. Assessing the reactivity of sodium alkyl-magnesiates towards quinoxaline: single electron transfer (SET) vs. nucleophilic alkylation processes.

    Science.gov (United States)

    Livingstone, Zoe; Hernán-Gómez, Alberto; Baillie, Sharon E; Armstrong, David R; Carrella, Luca M; Clegg, William; Harrington, Ross W; Kennedy, Alan R; Rentschler, Eva; Hevia, Eva

    2016-04-14

    By exploring the reactivity of sodium butyl-magnesiate (1) supported by the bulky chelating silyl(bisamido) ligand {Ph2Si(NAr*)2}(2-) (Ar* = 2,6-iPr2-C6H3) towards Quinoxaline (Qx), the ability of this bimetallic system to effectively promote SET processes has been disclosed. Thus 1 executes the single-electron reduction of Qx affording complex (2) whose structure in the solid state contains two quinaxolyl radical anions Qx˙ stabilised within a dimeric magnesiate framework. Combining multinuclear NMR and EPR measurements with DFT calculations, new insights into the constitution of 2 in solution and its magnetic behaviour have been gained. Further evidence on the SET reactivity of 1 was found when it was reacted with nitroxyl radical TEMPO which furnished contacted ion pair sodium magnesiate [(Ph2Si(NAr*)2)Mg(TEMPO(-))Na(THF)3] (4) where both metals are connected by an alkoxide bridge, resulting from reduction of TEMPO. The role that the different ligands present in 1 can play in these new SET reactions has also been assessed. Using an amination approach, the Bu group in 1 can be replaced by the more basic amide TMP allowing the isolation of (3) which was characterised by multinuclear NMR and X-ray crystallography. (1)H NMR monitoring of the reaction of 3 with Qx showed its conversion to 2, leaving the hydrogen atoms of the heterocycle untouched. Contrastingly, using sodium homoalkyl magnesiate [NaMg(CH2SiMe3)3] (5) led to the chemoselective C2 alkylation of this heterocycle, suggesting that the presence of the steric stabiliser {Ph2Si(NAr*)2}(2-) on the mixed-metal reagent is required in order to facilitate the Qx reduction.

  19. 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.

  20. Synthesis of K2MnAl11O19 Catalysts and Investigation on Their Catalytic Activity of Methane Combustion%K2MnAl11O19六铝酸盐催化剂的制备及其催化甲烷燃烧性能的研究

    Institute of Scientific and Technical Information of China (English)

    郑建东; 任晓光; 葛秀涛

    2012-01-01

    KzMnAlnO19 catalysts were prepared by co-precipitation method, hydrolysis of metal alkoxide method and reverse microemulsion method. The effects of preparation methods on crystal structure and properties of the catalysts were investigated by means of XRD,BET, TG-DTA and activity evaluation for methane combustion. The results showed that the catalyst with good crystallinity was obtained after calcination at 1200"C for 4h by the three methods. At the same time the catalysts have the high catalytic activity and stability. The catalyst prepared by reverse microemulsion method maintains high surface area and has a higher catalytic activity with T10% as 458℃ and T90% as 676℃ for methane combustion.%采用共沉淀法、溶胶-凝胶法和反相微乳液法制备六铝酸盐催化剂K2 MnAl11O9,利用XRD、BET和TGDTA技术及甲烷燃烧活性对催化剂进行了表征和活性验证.结果表明,3种方法所制备催化剂经1200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中反相微乳液法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性,起燃温度T10%=458℃,至676℃(T90%)甲烷完全转化.

  1. Composite Aerogel Multifoil Protective Shielding

    Science.gov (United States)

    Jones, Steven M.

    2013-01-01

    New technologies are needed to survive the temperatures, radiation, and hypervelocity particles that exploration spacecraft encounter. Multilayer insulations (MLIs) have been used on many spacecraft as thermal insulation. Other materials and composites have been used as micrometeorite shielding or radiation shielding. However, no material composite has been developed and employed as a combined thermal insulation, micrometeorite, and radiation shielding. By replacing the scrims that have been used to separate the foil layers in MLIs with various aerogels, and by using a variety of different metal foils, the overall protective performance of MLIs can be greatly expanded to act as thermal insulation, radiation shielding, and hypervelocity particle shielding. Aerogels are highly porous, low-density solids that are produced by the gelation of metal alkoxides and supercritical drying. Aerogels have been flown in NASA missions as a hypervelocity particle capture medium (Stardust) and as thermal insulation (2003 MER). Composite aerogel multifoil protective shielding would be used to provide thermal insulation, while also shielding spacecraft or components from radiation and hypervelocity particle impacts. Multiple layers of foil separated by aerogel would act as a thermal barrier by preventing the transport of heat energy through the composite. The silica aerogel would act as a convective and conductive thermal barrier, while the titania powder and metal foils would absorb and reflect the radiative heat. It would also capture small hypervelocity particles, such as micrometeorites, since it would be a stuffed, multi-shock Whipple shield. The metal foil layers would slow and break up the impacting particles, while the aerogel layers would convert the kinetic energy of the particles to thermal and mechanical energy and stop the particles.

  2. 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.

  3. Mechanistic insights into the formation of acetaldehyde and diethyl ether from ethanol over support VO{sub x}, MoO{sub x}, and WO{sub x} catalysts.

    Energy Technology Data Exchange (ETDEWEB)

    Nair, H.; Gatt, J. E.; Miller, J. T.; Baertsch, C. D. (Chemical Sciences and Engineering Division); (Purdue Univ.)

    2011-04-01

    Catalytic pathways are described for reactions of ethanol to acetaldehyde by oxidative dehydrogenation and of ethanol to diethyl ether by condensation over VO{sub x}-Al{sub 2}O{sub 3}, MoO{sub x}-Al{sub 2}O{sub 3}, and WO{sub x}-Al{sub 2}O{sub 3}. Isotopic labeling shows that acetaldehyde formation occurs via rate-determining C-H bond cleavage of the CH{sub 2} group in an adsorbed alkoxide followed by removal of surface oxygen in a Mars and van Krevelen redox mechanism (as confirmed by in situ X-ray absorption, diffuse reflectance infra-red Fourier transform spectroscopy and UV-visible spectroscopy); diethyl ether formation occurs in parallel via coupling and condensation of two adjacent ethoxy species. Using a combination of in situ spectroscopic and kinetic analysis, catalyst properties influencing the formation of acetaldehyde and ether from the common adsorbed ethoxy intermediate are elucidated. X-ray absorption analysis during anaerobic ethanol titration is used to preclude the involvement of terminal MO bonds during the reaction. A study of the activity of catalysts with the same MoO{sub x} domain size on Al{sub 2}O{sub 3}, TiO{sub 2}, and CeO{sub 2} supports and binary oxides of MoO{sub x} and WO{sub x} on Al{sub 2}O{sub 3} are used to prove that the active redox oxygen for acetaldehyde formation is the oxygen atom linking the active metal oxide domain to the support oxide. Ether formation ability of the metal oxide is related to the electronegativity of the active metal atom.

  4. Mechanistic insights into the formation of acetaldehyde and diethyl ether from ethanol over supported VO{subx}, MoO{subx}, and WO{subx} catalysts.

    Energy Technology Data Exchange (ETDEWEB)

    Nair, H.; Gatt, J. E.; Miller, J. T.; Baertsch, C. D. (Chemical Sciences and Engineering Division); (Purdue University)

    2011-04-01

    Catalytic pathways are described for reactions of ethanol to acetaldehyde by oxidative dehydrogenation and of ethanol to diethyl ether by condensation over VO{sub x}-Al{sub 2}O{sub 3}, MoO{sub x}-Al{sub 2}O{sub 3}, and WO{sub x}-Al{sub 2}O{sub 3}. Isotopic labeling shows that acetaldehyde formation occurs via rate-determining C-H bond cleavage of the CH{sub 2} group in an adsorbed alkoxide followed by removal of surface oxygen in a Mars and van Krevelen redox mechanism (as confirmed by in situ X-ray absorption, diffuse reflectance infra-red Fourier transform spectroscopy and UV-visible spectroscopy); diethyl ether formation occurs in parallel via coupling and condensation of two adjacent ethoxy species. Using a combination of in situ spectroscopic and kinetic analysis, catalyst properties influencing the formation of acetaldehyde and ether from the common adsorbed ethoxy intermediate are elucidated. X-ray absorption analysis during anaerobic ethanol titration is used to preclude the involvement of terminal M{double_bond}O bonds during the reaction. A study of the activity of catalysts with the same MoO{sub x} domain size on Al{sub 2}O{sub 3}, TiO{sub 2}, and CeO{sub 2} supports and binary oxides of MoO{sub x} and WO{sub x} on Al{sub 2}O{sub 3} are used to prove that the active redox oxygen for acetaldehyde formation is the oxygen atom linking the active metal oxide domain to the support oxide. Ether formation ability of the metal oxide is related to the electronegativity of the active metal atom.

  5. Characterization of titanium oxynitride films deposited by low pressure chemical vapor deposition using amide Ti precursor

    Energy Technology Data Exchange (ETDEWEB)

    Song Xuemei; Gopireddy, Deepthi [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Takoudis, Christos G. [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)], E-mail: takoudis@uic.edu

    2008-07-31

    In this study, we investigate the use of an amide-based Ti-containing precursor, namely tetrakis(diethylamido)titanium (TDEAT), for TiN{sub x}O{sub y} film deposition at low temperature. Traditionally, alkoxide-based Ti-containing precursor, such as titanium tetra-isopropoxide (TTIP), along with NH{sub 3} is used for titanium oxynitride (TiN{sub x}O{sub y}) film deposition. When TTIP is used, at low temperatures it is difficult to form TiN{sub x}O{sub y} films with high N/O ratios. In this study, by using TDEAT, TiN{sub x}O{sub y} films are deposited on H-passivated Si (100) substrates in a cold wall reactor at 300 {sup o}C and 106 Pa. Rutherford backscattering spectroscopy analysis shows nitrogen incorporation in the TiN{sub x}O{sub y} films to be as high as 28 at.%. X-ray photoelectron spectroscopy analysis of as-deposited films confirms the formation of{sub .} TiN{sub x}O{sub y}, while Fourier transform infrared and Raman spectra indicate that the films have amorphous structure. Moreover, there is no detectable bulk carbon impurity and no SiO{sub 2} formation at the TiN{sub x}O{sub y}/Si interface. Upon annealing the as-deposited films in air at 750 deg. C for 30 min, they oxidize to TiO{sub 2} and crystallize to form a rutile structure with a small amount of anatase phase. Based on these results, TDEAT appears to be a promising precursor for both TiN{sub x}O{sub y} and TiO{sub 2} film deposition.

  6. Quasi-solid-state dye-sensitized solar cells employing nanocrystalline TiO{sub 2} films made at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Stathatos, Elias [Department of Electrical Engineering, Technological-Educational Institute of Patras, M. Alexandrou 1, GR-26334 Patras (Greece); Chen, Yongjun; Dionysiou, Dionysios D. [Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221-0071 (United States)

    2008-11-15

    Quasi-solid-state dye-sensitized solar cells with enhanced performance were made by using nanocrystalline TiO{sub 2} films without any template deposited on plastic or glass substrates at low temperature. A simple and benign procedure was developed to synthesize the low-temperature TiO{sub 2} nanostructured films. According to this method, a small quantity of titanium isopropoxide (TTIP) was added in an ethanolic dispersion of TiO{sub 2} powder consisting of nanoparticles at room temperature, which after alkoxide's hydrolysis helps to the connection between TiO{sub 2} particles and to the formation of mechanically stable thick films on plastic or glass substrates. Pure TiO{sub 2} films without any organic residuals consisting of nanoparticles were formed with surface area of 56 m{sup 2}/g and pore volume of 0.383 cm{sup 3}/g similar to that obtained for Degussa-P25 powder. The structural properties of the films were characterized by microscopy techniques, X-ray diffractometry, and porosimetry. Overall solar to electric energy conversion efficiencies of 5.3% and 3.2% (under 1sun) were achieved for quasi-solid-state dye-sensitized solar cells employing such TiO{sub 2} films on F:SnO{sub 2} glass and ITO plastic substrates, respectively. Thus, the quasi-solid-state device based on low-temperature TiO{sub 2} attains a conversion efficiency which is very close to that obtained for cells consisting of TiO{sub 2} nanoparticles sintered at high temperature. (author)

  7. Combinatorial Approach for the Discovery of New Scintillating Materials SBIR Phase I Final Report Report # DOE/ER/84310

    Energy Technology Data Exchange (ETDEWEB)

    Cronin, J P; Agrawal, A; Tonazzi, J C

    2006-08-22

    The combinatorial approach for the discovery of new scintillating materials has been investigated using the wet-chemical (sol-gel) synthesis methods. Known scintillating compounds Lu2SiO5 (LSO) and (LuAl)O3 (LAO) and solid solutions in the systems of Lu2O3 -Y2O3 – SiO2 (CeO2-doped) (LYSO) and Lu2O3 -Y2O3 – Al2O3 (CeO2 –doped) (LYAO) were synthesized from sol-gel precursors. Sol-gel precursors were formulated from alkoxides and nitrates and acetates of the cations. Sol-gel solution precursors were formulated for the printing of microdot arrays of different compositions in the above oxide systems. Microdot arrays were successfully printed on C-cut and R-cut sapphire substrates using Biodot printer at Los Alamos National Laboratory (LANL). The microdot arrays were adherent and stable after heat-treating at 1665oC and had an average thickness of around 2m. X-ray fluorescence elemental mapping showed the arrays to be of the correct chemical composition. Sintered microdots were found to be highly crystalline by microscopic observation and X-ray diffraction. Scintillation was not clearly detectable by visual observation under UV illumination and by video observation under the scanning electron beam of an SEM. The microdots were either poorly scintillating or not scintillating under the present synthesis and testing conditions. Further improvements in the synthesis and processing of the microdot arrays as well as extensive scintillation testing are needed.

  8. Hydrogen storage on Ni/Al/sub 2/O/sub 3/ nano-composite for fuel application

    International Nuclear Information System (INIS)

    Nanomaterials are now emerging as an alternative to the conventional bulk materials due to their unprecedented physical and chemical properties. A material is said to be nano if the particle size is less than 100 nm in at least one dimension. From the great many advantages of nanomaterials one is the opportunity to control the microstructure (composition, structure, shape and size) at nano-meter level scale. The properties of nanomaterials change as a function of size of the particles. The smaller size allows large specific surface area which enables them excellent candidates for adsorption applications. This presentation highlights the synthesis of Ni/Al/sub 2/O/sub 3/ nano-composite and its application for hydrogen adsorption (storage), one of the burning topics of the present times. A dynamic chemical vapor deposition (CVD) technique was used for the synthesis of Ni/Al/sub 2/O/sub 3/ nano-composite. The material was achieved by reducing Ni+2 to Ni0 under the steady stream of hydride-modified aluminum alkoxides ((H2Al(OtBu)2). The CVD reactor has the advantage of dynamic vacuum removing the byproduct as soon as produced and thus hindering the contamination of the resulting Ni/Al/sub 2/O/sub 3/ nano-composite. The physical (analytical) characterization techniques revealed the formation of metallic nickel dispersed in alumina (Ni/Al/sub 2/O/sub 3/) matrix. The material has sufficient porosity which is revealed by the scanning electron microscopic photographs. The material was tested for possible hydrogen storage using homemade Sievert's type apparatus and it was found that approximately 2.9 wt.% (w/w %) hydrogen can be stored upon the Ni/Al/sub 2/O/sub 3/ nano-composite. Although the amount of hydrogen stored is below of the required amount for onboard applications. However, the study will open new dimension in terms of hydrogen storage materials. (author)

  9. Study on the decomposition mechanism of alkyl carbonate on lithium metal by pyrolysis-gas chromatography-mass spectroscopy

    Science.gov (United States)

    Mogi, Ryo; Inaba, Minoru; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi

    The surface films formed on deposited lithium in electrolyte solutions based on ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were analyzed by pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS). In 1 M LiClO 4/EC, the main component of the surface film was easily hydrolyzed to give ethylene glycol after exposure to air, and hence was considered to have a chemical structure of ROCH 2CH 2OR', of which OR and OR' are OLi or OCO 2Li. Ethylene oxide, acetaldehyde, and 1,4-dioxane were detected in decomposition products, and they were considered to have been formed by pyrolysis of ROCH 2CH 2OR' in the pyrolyzer. The presence of ethanol in decomposition products confirmed that ring cleavage at the CH 2O bonds of EC occurs by one electron reduction. In addition, the presence of methanol implied the cleavage of the CC bond of EC upon reduction. From the surface films formed in 1 M LiClO 4/DEC and /DMC, ethanol and methanol, respectively, were detected, which suggested that corresponding lithium alkoxides and/or lithium alkyl carbonates were the main components. In 1 M LiClO 4/EC+DEC (1:1), EC dominantly decomposed to form the surface film. The surface film formed in 1 M LiPF 6/EC+DEC (1:1) contained a much smaller amount of organic compounds.

  10. 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.

  11. The mechanical robustness of atomic-layer- and molecular-layer-deposited coatings on polymer substrates

    Science.gov (United States)

    Miller, David C.; Foster, Ross R.; Zhang, Yadong; Jen, Shih-Hui; Bertrand, Jacob A.; Lu, Zhixing; Seghete, Dragos; O'Patchen, Jennifer L.; Yang, Ronggui; Lee, Yung-Cheng; George, Steven M.; Dunn, Martin L.

    2009-05-01

    The mechanical robustness of atomic layer deposited alumina and recently developed molecular layer deposited aluminum alkoxide ("alucone") films, as well as laminated composite films composed of both materials, was characterized using mechanical tensile tests along with a recently developed fluorescent tag to visualize channel cracks in the transparent films. All coatings were deposited on polyethylene naphthalate substrates and demonstrated a similar evolution of damage morphology according to applied strain, including channel crack initiation, crack propagation at the critical strain, crack densification up to saturation, and transverse crack formation associated with buckling and delamination. From measurements of crack density versus applied tensile strain coupled with a fracture mechanics model, the mode I fracture toughness of alumina and alucone films was determined to be KIC=1.89±0.10 and 0.17±0.02 MPa m0.5, respectively. From measurements of the saturated crack density, the critical interfacial shear stress was estimated to be τc=39.5±8.3 and 66.6±6.1 MPa, respectively. The toughness of nanometer-scale alumina was comparable to that of alumina thin films grown using other techniques, whereas alucone was quite brittle. The use of alucone as a spacer layer between alumina films was not found to increase the critical strain at fracture for the composite films. This performance is attributed to the low toughness of alucone. The experimental results were supported by companion simulations using fracture mechanics formalism for multilayer films. To aid future development, the modeling method was used to study the increase in the toughness and elastic modulus of the spacer layer required to render improved critical strain at fracture. These results may be applied to a broad variety of multilayer material systems composed of ceramic and spacer layers to yield robust coatings for use in chemical barrier and other applications.

  12. Nano-casted Metal Oxide Aerogels as Dual Purpose Structural Components for Space Exploration

    Science.gov (United States)

    Vassilaras, Plousia E.

    2004-01-01

    NASA missions and space exploration rely on strong, ultra lightweight materials. Such materials are needed for building up past and present space vehicles such as the Sojourner Rover (1997) or the two MERs (2003), but also for a number of components and/or systems including thermal insulators, Solar Sails, Rigid Aeroshells, and Ballutes. The purpose of my internship here at Glenn Research Center is to make dual purpose materials; materials that in addition to being lightweight have electronic, photophysical and magnetic properties and, therefore, act as electronic components and sensors as well as structural components. One type of ultra lightweight material of great interest is aerogels, which have densities ranging from 0.003 g/cc to 0.8 g/cc . However, aerogels are extremely fragile and, as a result, have limited practical applications. Recently, Glenn Research Center has developed a process of nano-casting polymers onto the inorganic network of silica-based aerogels increasing the strength 300 fold while only increasing the density 3 fold. By combining the process of nano-casting polymers with inorganic oxide networks other than silica, we are actively pursuing lightweight dual purpose materials. To date, thirty different inorganic oxide aerogels have been prepared using either standard sol-gel chemistry or a non-alkoxide method involving metal chloride precursors and an epoxide; epichlorohydrin, propylene oxide or trimethylene oxide, as proton scavengers. More importantly, preliminary investigations show that the residual surface hydroxyl groups on each of these inorganic oxide aerogels can be successfully crosslinked with urethane. In addition to characterizing physical and mechanical properties such as density, strength and flexibility, each of these metal oxide aerogels are being characterized for thermal and electronic conductivity and magnetic and optical properties.

  13. In situ spectroscopic applications to the study of rechargeable lithium batteries. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Barbour, R.; Kim, Sunghyun; Tryk, D.; Scherson, D.A. [Case Western Reserve Univ., Cleveland, OH (United States). Dept of Chemistry

    1993-08-01

    In situ attenuated total reflection Fourier transform infrared spectroscopy (ATR/FTIR) has been employed to examine the reactivity of lithium toward polyethylene oxide (PEO) at ca. 60{degree}C. Uncertainties regarding the cleanliness of the Li surfaces were, minimized by electrodepositing a film of metallic Li directly onto a thin layer of gold (ca. 60 {Angstrom}) vapor deposited on a Ge ATR optical element during the spectroscopic measurements. The ATR/FTIR features observed upon stripping the Li layer were consistent with the formation of alkoxide-type moieties resulting from the Li-induced cleavage of the ether-type functionalities. Electronic and structural aspects of the electrochemical insertion of lithium from non-aqueous electroyltes into FeS{sub 2} have been investigated using in situ Fe K-edge X-ray absorption fine structure (XAFS). The results obtained indicate that the incorporation of Li{sup +} in the pyrite lattice brings about a marked decrease in the amplitude of the extended XAFS (EXAFS) oscillations, particularly for shells associated with distant atoms and a rounding of the, X-ray absorption near edge structure (XANES) region. An analysis of the EXAFS spectra yielded a value for the FeS distance of 2.29 {plus_minus} 0.02 {Angstrom}. On this basis and additional in situ room temperature {sup 57}Fe Mossbauer effect spectroscopy data for the same system it has been proposed that the electrically formed material involves a highly disordered (possibly amorphous) form of Fe{sub l-x}S (with Li+ counterbalancing the charge).

  14. 多孔TiO2薄膜的制备及其光催化活性%Preparation and Photo-catalytic Activity of the Porous TiO2 Thin Films

    Institute of Scientific and Technical Information of China (English)

    邹旭华; 齐世学; 刘雪梅; 于文娟; 安立敦

    2001-01-01

    The porous TiO2 thin films on both of carriers, glass sheet and glass fiber, are prepared from titanium alkoxide solution containing polyethylene glycol (PEG) by a dip-coating technique. The photo-catalytic degradation experiments show that methyl orange aqueous solution is efficiently decolorized in the presence of the porous TiO2 thin films by illumination with a high-pressure mercury lamp. The photo-catalytic activity of the TiO2 thin films is enhanced with the increase of the coating cycles or the PEG addition to the precursor solution. Under the same condition, the photo-catalytic activity of the porous TiO2 thin films on glass fiber is better than that of the porous TiO2 thin films using glass sheet as carriers.%采用溶胶-凝胶法在玻璃片和玻璃纤维两种基体上制备了多孔TiO2薄膜.对甲基橙水溶液的光催化降解实验表明:在一定范围内,随着TiO2镀层层数的增加,薄膜的光催化活性增强;且相同条件下,以玻璃纤维为基体的薄膜的光催化活性明显优于以玻璃片为基体的薄膜的活性.

  15. Molecular designing of precursors for chemical vapor deposition

    International Nuclear Information System (INIS)

    Both tin oxide and antimony oxide, can act as gas sensing material whose activity/selectivity is enhanced by the incorporation of a second metal. We are interested in the formation of bimetallic and trimetallic carboxylates and alkoxides which can be used as single source precursors for such mixed metal oxides. Sb(dmae)/sub 3/ (dmae=OCH/sub 2/CH/sub 2/(CH/sub 3/)sub 2/ has been prepared from Sb(OC/sub 2/H/sub 5/)/sub 3/ and Hdmae and used to generate the bimetallic materials Sb(dmae)/sub 3/Cd(acac)/sub 2/. Sn(acac)/sub 2/ hydrolyses to yield crystalline cage Sn/sub 4/O/sub 6/(dmae)/sub 4/. Sn(dmae)/sub 2/ can also be used to generate bimetallic materials such as [Sn(dmae)/sub 2/ Cd(acac)/sub 2/]/sub 2/]. Bimetallic and trimetallic carboxylates of general formula [R/sub 3/Ge-CHRCH/sub 2/COO]/sub 4-n/SnRn. [Where R=CH/sub 3/, C/sub 2/H/sub 5/, C/sub 6/H/sub 5/, tolyl, cyclohexyl, (CH/sub 3/)/sub 3/ Si CH/sub 2/-etc.] have been prepared and characterized by various analytic techniques. Chemical vapor deposition using Sb(dmae)/sub 3/ Cd(acac)/sub 2/ and various bimetallic carboxylates yield thin films of Cd/sub 2/Sb/sub 2/O/sub 7/ and SnOGeO respectively. (author)

  16. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    Science.gov (United States)

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology. PMID:26891039

  17. 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

    2014-10-01

    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.

  18. Interim report on task 1.2: near equilibrium processing requirements - attrition milling part 1 of 2 to Lawrence Livermore National for contract b345772

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, M W A; Vance, E R; Day, R A; Eddowes, T; Moricca, S

    2000-04-30

    The objective of Task 1.2 has only partly been achieved as the work on Pu/U-formulations and to a significant degree on Th/U-formulations has been performed under grinding/blending conditions that did not replicate plant-like fabrication processes, particularly in the case with the small glovebox attritor. Nevertheless the results do show that actinide-rich particles, not present in specimens made via the alkoxide-route (equilibrium conditions), occur when the grinding process is not efficient enough to ensure that high-fired PuO{sub 2}, ThO{sub 2} and UO{sub 2} particles are below a critical size. Our current perception is that the critical size for specimens sintered at 1350 C for 4 hours is about 5 {micro}m in diameter. The critical size is difficult to estimate, as it is equal to the starting diameter of actinide oxides just visible within brannerite regions. Our larger scale attritor experiments as well as experience with wet and dry ball milling suggests that acceptable mineralogy and microstructure can be obtained by dry milling via attritor and ball mills. This is provided that appropriate attention is paid to the size and density of the grinding media, grinding additives that reduce caking of the powder, and in the case of attritors the grinding speed and pot setup. The ideal products for sintering are free flowing granules of {approx} 100 {micro}m containing constituents ground to about 1 {micro}m to ensure homogeneity and equilibrium mineralogy.

  19. Thermal chemistry of the Cu-KI5 atomic layer deposition precursor on a copper surface

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Qiang; Zaera, Francisco, E-mail: zaera@ucr.edu [Department of Chemistry, University of California, Riverside, California 92521 (United States)

    2015-01-01

    The thermal chemistry of a Cu(I) ketoiminate complex, Cu-KI5, resulting from the modification of the known Air Products CupraSelect{sup ®} copper CVD precursor Cu(hfac)(tmvs) designed to tether the two ligands via an isopropoxide linker, was studied under ultrahigh vacuum on a Cu(110) single-crystal surface by using a combination of temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy. Adsorption at low temperatures was determined to take place via the displacement of the vinyl ligand by the surface. Molecular desorption was seen at 210 K, and the evolution of Cu(II)-KI5{sub 2} was established to take place at 280 K, presumably from a disproportionation reaction that also leads to the deposition of Cu(0). Other sets of desorption products were seen at 150, 250, and 430 K, all containing copper atoms and small organic moieties with molecular masses below 100 amu. The latter TPD peak in particular indicates significant fragmentation of the ligands, likely at the C–N bond that holds the vinylsilane-isopropoxide moiety tethered to the ketoimine fragment, and possibly also at the union between the vinylsilane and the alkoxide linker. The 430 K temperature measured for this chemistry may set an upper limit for clean Cu film deposition, but since reactivity on the surface was also found to be inhibited at higher surface coverages, it may be delayed to higher temperatures under atomic layer deposition conditions.

  20. Formation and microstructural analysis of 3-dimensional titanium oxide structures via large surface electron beam irradiation

    International Nuclear Information System (INIS)

    Recently, in photo electronic devices industry, titanium oxide which was known to have good optical and electrical characteristic's been studied in the microstructural aspect to increase the conversion efficiency, such as making variable architecture, coating the titanium oxide nano-tube with the quantum dots which have higher band gap materials than this, etc. However, the process of making 3-dimensional titanium oxide structure with general deposition system such as hydrothermal growth, CVO, PVD and ALD had more variables and longer time consumption to make nano structures than electron beam irradiation case. Herein, we proceed with making new titanium oxide nano-screen-testing electron beam irradiation. The metal alkoxide composed of the 1 mol of titanium iso-propoxide and the 1 mol of acetylation reacted with water in propylene glycol methyl ether acetate and isopropyl alcohol solvent. After this process which made the bonding among Ti, O and other organics, the polymer solution was deposited on various types of substrate, such as anodized aluminum oxide mail. Kist. ac., Ag nano dots on SiO2 thin film, Au nano dots on SiO2 thin film, etc. The electron beam irradiation was progressed with the vertical accelerator facility of EB tech which was the company in Dijon, Korea The shape, microstructure and chemical composition of the irradiated polymers were characterized using TEM, XRD, Sem and EDS. The three types of Ti-Ox 3-dimensional structure were made; nano dot cluster, spike-like structure and dendrite structure. Each type of these structures was composed of different mircrostructures. Especially, the formation the 3-dimensional structures via electron beam irradiation was not only effected by the electron beam irradiation conditions but also effected by solution concentrate, conductivity and surface energy of substrate

  1. Dehydration of 1-octadecanol over H-BEA: A combined experimental and computational study

    Energy Technology Data Exchange (ETDEWEB)

    Song, Wenji; Liu, Yuanshuai; Barath, Eszter; Wang, Lucy; Zhao, Chen; Mei, Donghai; Lercher, Johannes A.

    2016-02-05

    Liquid phase dehydration of 1-octdecanol, which is intermediately formed during the hydrodeoxygenation of microalgae oil, has been explored in a combined experimental and computational study. The alkyl chain of C18 alcohol interacts with acid sites during diffusion inside the zeolite pores, resulting in an inefficient utilization of the Brønsted acid sites for samples with high acid site concentrations. The parallel intra- and inter- molecular dehydration pathways having different activation energies pass through alternative reaction intermediates. Formation of surface-bound alkoxide species is the rate-limiting step during intramolecular dehydration, whereas intermolecular dehydration proceeds via a bulky dimer intermediate. Octadecene is the primary dehydration product over H-BEA at 533 K. Despite of the main contribution of Brønsted acid sites towards both dehydration pathways, Lewis acid sites are also active in the formation of dioctadecyl ether. The intramolecular dehydration to octadecene and cleavage of the intermediately formed ether, however, require strong BAS. L. Wang, D. Mei and J. A. Lercher, acknowledge the partial support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC). EMSL is a national scientific user facility located at Pacific Northwest National Laboratory (PNNL) and sponsored by DOE’s Office of Biological and Environmental Research.

  2. Synthesis, structure and ESR studies of Mg doped ZnAlO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Cakiroglu, O. [Istanbul University, Hasan Ali Yucel Education Faculty, Beyazit, 34452 Istanbul (Turkey); Acikgoz, M. [Bahcesehir University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, Besiktas, 34349 Istanbul (Turkey); Arda, L., E-mail: lutfi.arda@bahcesehir.edu.tr [Bahcesehir University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, Besiktas, 34349 Istanbul (Turkey); Akcan, D. [Bahcesehir University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, Besiktas, 34349 Istanbul (Turkey); Dogan, N. [Gebze Institute of Technology, Department of Physics, 41400 Gebze/Kocaeli (Turkey)

    2015-01-01

    Zn{sub 0.98−x}Mg{sub x}Al{sub 0.02}O solutions with different (x=0.05, 0.10, 0.15, and 0.20) compositions were synthesized by the sol–gel technique using Zn, Mg and Al based alkoxide. The effects of highly Mg doping ratio on structure and magnetic properties were investigated systematically. The phase and the crystal structure of the Zn{sub 0.98−x}Mg{sub x}Al{sub 0.02}O nanoparticles were characterized using X-ray diffraction. Scanning Electron Microscope and X-ray diffraction were utilized to understand the size and microstructure of samples. We observed the particle sizes of nanoparticles between 80 nm and 100 nm range. Furthermore, ESR spectra of Zn{sub 0.98−x}Mg{sub x}Al{sub 0.02}O nanoparticles were collected at room temperature on a Bruker EMX model X-band spectrometer operating at a frequency of 9.50 GHz. It is observed that the critical concentration of Mg, x=0.1, has minimum g-factor and maximum line-width (W). - Highlights: • Zn{sub 0.98−x}Mg{sub x}Al{sub 0.02}O{sub ,} (0.05≤x≤0.20) nanoparticles were prepared by sol–gel technique. • The Mg concentration is increased, the agglomeration and malting of nanoparticles increase. • Rietveld analysis of ZnMgAlO shows single phase (ZnO) for x<0.2 concentration. • The critical concentration of Mg is x=0.1 to have minimum g-factor and maximum line-width W.

  3. Polymerization of 1,3-Conjugated Dienes with Rare-Earth Metal Precursors

    Science.gov (United States)

    Zhang, Zhichao; Cui, Dongmei; Wang, Baoli; Liu, Bo; Yang, Yi

    This chapter surveys the publications except patents related to cis-1,4-, trans-1,4-, 3,4-regio-, and stereoselective polymerizations of 1,3-conjugated dienes with rare-earth metal-based catalytic systems during the past decade from 1999 to 2009. The concerned catalyst systems are classified into the conventional Ziegler-Natta catalysts, the modified Ziegler-Natta catalysts, and the single-site cationic systems composed of lanthanocene and noncyclopentadienyl precursors, respectively. For the conventional Ziegler-Natta catalysts of the most promising industry applicable recipe, the multicomponents based on lanthanide carboxylate or phosphate or alkoxide precursors, research works concern mainly about optimizing the catalyst preparation and polymerization techniques. Special emphases are put on the factors that influence the catalyst homogeneority, catalytic activity and efficiency, as well as cis-1,4-selectivity. Meanwhile, tailor-made lanthanide aryloxide and amide complexes are designed and fully characterized to mimic the conventional Ziegler-Natta catalysts, anticipated to elucidate the key processes, alkylation and cationization, for generating the active species. Regarding to the single-site catalytic systems generally comprising well-defined complexes containing lanthanide-carbon bonds, investigations cover their versatile catalytic activity and efficiency, and the distinguished regio- and stereoselectivity for both polymerization of dienes and copolymerization of dienes with alkenes. The correlation between the sterics and electronics of ligands and the molecular structures of the complexes and their catalytic performances are highlighted. The isolation of the probable active species in these polymerization processes from the stoichiometric reactions of the precursors with activators will be presented.

  4. Synthesis of nano titania particles embedded in mesoporous SBA-15: Characterization and photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jun [Department of Chemistry, Jinan University, Guangzhou 510632 (China)]. E-mail: tyangj@jnu.edu.cn; Zhang Jun [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Zhu Liwei [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Chen Shaoyuan [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Zhang Yuanming [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Tang Yu [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Zhu Yulei [Department of Chemistry, Jinan University, Guangzhou 510632(China); State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Li Yongwang [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2006-09-21

    Supported nanocrystalline titanium dioxide (TiO{sub 2}) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO{sub 2}/SBA-15 composites with various TiO{sub 2} loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO{sub 2} did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 deg. C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO{sub 2} grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO{sub 2}/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO{sub 2} nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites.

  5. 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

  6. Methane dry reforming catalysts for the production of hydrogen and carbon monoxide

    International Nuclear Information System (INIS)

    The reaction of carbon dioxide reforming of methane (dry reforming) is a very attractive way to convert low-cost reactants in synthesis gas (CO + H2).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 H2: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 HNO3. A1C0: characteristics: thermal decomposition. A1C0H: characteristics: thermal decomposition and subsequent hydrothermal treatment.To sum up, three Ni-A12O3 catalysts, three Ni-Rh-A12O3 catalysts, and three Ni-Ru-A12O3 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 was studied by

  7. Synthesis and characterization of technetium(V) complexes with amine, alcoholate, and chloride ligands

    International Nuclear Information System (INIS)

    Two general routes for the preparation of technetium complexes with aromatic amine, chloride, and alkoxide ligands are presented. The reactions of the tetrachlorooxotechnetate(V) anion of (n-Bu4N)[TcOCl4] with pyridine in tetrahydrofuran/alcohol solvent or of the dioxotetrakis(pyridine)technetium(V) cation of [TcO2(py)4]Cl with LiCl in sulfuric acid/alcohol both yield a neutral alkoxydichlorooxobis(pyridine)technetium(V) complex. The same isomer appears to result from either route. The analogous thiazole derivatives may be prepared in a like manner. The complex chloro(1,2-ethanediolato)oxo(1,10-phenanthroline)technetium(V), TcOCl(C2H4O2)(C12H8N2), is prepared from (n-Bu4N)[TcOCl4] with 1,2-ethanediol and 1,10-phenanthroline in methanol. This complex was characterized by ir, uv/vis, and 1H and 99Tc NMR spectroscopies and by fast atom bombardment mass spectrometry. Further insight into the bonding in this complex comes from the single-crystal x-ray structure determination. The space group is monoclinic, P21/c, with a = 7.440 (2) angstrom, b = 8.928 (3) angstrom, c = 21.355 (4) angstrom, β = 92.48 (2)degree, V = 1417.2 (7) angstrom 3, and Z = 4. The structure was solved by standard methods and refined to R = 0.051 and Rw = 0.036 based on 1859 reflections. The oxo and chloride ligands are mutually cis in the highly distorted octahedral coordination sphere. The unusually long Tc-Cl bond length (2.418 (2) angstrom) is attributed to a trans influence exerted by the coordinated diolate. This effect combined with short lengths for the C-C bond (1.491 (1) angstrom) and for the O-Tc-O linkage (1.924 (4), 1.902 (3) angstrom) suggests partial multiple bonding between the technetium and the diolate. 38 references, 2 figures, 3 tables

  8. Bridging silyl groups in sigma-bond metathesis and [1, 2] shifts. An experimental and computational study of the reaction between cerium metallocenes and MeOSiMe3

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-21

    The reaction of Cp'2CeH (Cp' = 1,2,4-(Me3C)3C5H2 ) with MeOSiMe3 gives Cp'2CeOMe and HSiMe3 and the reaction of the metallacycle, Cp'[(Me3C)2C5H2C(Me) 2CH2]Ce, with MeOSiMe3 yields Cp'2CeOCH2SiMe3, formed from hypothetical Cp'2CeCH2OSiMe3 by a [1, 2] shift also known as a silyl-Wittig rearrangement. Although both cerium products are alkoxides, they are formed by different pathways. DFT calculations on the reaction of the model metallocene, Cp2CeH, and MeOSiMe3 show that the lowest energy pathway is a H for OMe exchange at Ce that occurs by way of a sigma-bond metathesis transition state as SiMe3 exchanges partners. The formation of Cp2CeOCH2SiMe3 occurs by way of a low activation barrier [1, 2]shift of the SiMe3 group in Cp2CeCH2OSiMe3. Calculations on a model metallacycle, Cp[C5H4C(Me)2CH2]Ce, show that the metallacycle favors CH bond activation over sigma-bond metathesis involving the transfer of the SiMe3 group in good agreement with experiment. The sigma-bond metathesis involving the transfer of SiMe3 and the [1, 2]shift of SiMe3 reactions have in common a pentacoordinate silicon at the transition states. A molecular orbital analysis illustrates the connection between these two Si-O bond cleavage reactions and traces the reason why they occur for a silyl but not for an alkyl group to the difference in energy required to form a pentacoordinate silicon or carbon atom in the transition state. This difference clearly distinguishes a silyl from an alkyl group as shown in the study of"Pyrolysis of Tetramethylsilane Yielding Free d-orbitals by Seyferth and Pudvin in ChemTech 1981, 11, 230-233".

  9. Microwave characteristics of sol-gel based Ag-doped (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyoung-Tae; Kim, Cheolbok [Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611 (United States); Senior, David E. [Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611 (United States); Department of Electrical and Electronic Engineering, Universidad Tecnológica de Bolívar Cartagena, 130011 Colombia (Colombia); Kim, Dongsu [Packaging Research Center, Korea Electronics Technology Institute, Gyeonggi-do, 463-816 (Korea, Republic of); Yoon, Yong-Kyu, E-mail: ykyoon@ece.ufl.edu [Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2014-08-28

    Dielectric Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} (BST) thin films with a different concentration of Ag-dopant of 0.5, 1, 1.5, 2, 3, and 5 mol % have been prepared using an alkoxide-based sol-gel method on a Pt(111)/TiO{sub 2}/SiO{sub 2}/Si substrate and their surface morphology and crystallinity have been examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, respectively. An on-chip metal-insulator-metal capacitor has been fabricated with the prepared thin film ferroelectric sample. Concentric coplanar electrodes are used for high frequency electrical characterization with a vector network analyzer and a probe station. The SEM images show that increasing Ag doping concentration leads to a decrease in grain size. XRD reveals that the fabricated films show good BST crystallinity for all the concentration while a doping concentration of 5 mol % starts to show an Ag peak, implying a metallic phase. Improved microwave dielectric loss properties of the BST thin films are observed in a low Ag doping level. Especially, BST with an Ag doping concentration of 1 mol % shows the best properties with a dielectric constant of 269.3, a quality factor of 48.1, a tunability at the electric field of 100 kV/cm of 41.2 %, a leakage-current density of 1.045 × 10{sup −7}A/cm{sup 2} at an electric field of 100 kV/cm and a figure of merit (defined by tunability (%) divided by tan δ (%)) of 19.59 under a dc bias voltage of 10 V at 1 GHz. - Highlights: • High quality Ag-doped Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} (BST) thin films were derived by the sol-gel method. • Doped Ag replaced the A site ions in the ABO{sub 3} type structure. • Doped Ag helped lower leakage current by filling oxygen vacancies, which is a leakage path. • Microwave characteristics of low dielectric loss and good tunability were confirmed. • Great potential is envisioned for low loss tunable microwave applications.

  10. 锌掺杂多孔SiO2/TiO2薄膜制备及光催化性能研究%Preparation of Zn-doped SiO2/TiO2 thin films by sol-gel processing and their photocatalytic properties

    Institute of Scientific and Technical Information of China (English)

    胡张顺; 姚伯龙; 鲍雪钦

    2013-01-01

    锌掺杂多孔SiO2/TiO2(多孔 Zn-SiO2/TiO2)复合薄膜自清洁玻璃以含聚乙二醇的钛醇盐和硅醇盐的复合溶胶前驱体通过浸渍提拉法制备.结果表明,在TiO2薄膜中添加SiO2可抑制TiO2晶粒长大,并提高TiO2薄膜的亲水性;随着聚乙二醇添加量的增加,锌掺杂多孔SiO2/TiO2薄膜的孔隙增多,表面积增大;经500℃煅烧的多孔Zn-SiO2/TiO2复合薄膜中,TiO2主要为催化效率高的锐钛矿相;多孔Zn-SiO2/TiO2复合薄膜表观光催化降解速率明显高于未掺锌多孔SiO2/TiO2薄膜.%The porous Zn-doped SiO2/TiO2(porous Zn-SiO2/TiO2) composite thin films on the glass substrate were prepared from alkoxide solutions containing polyethylene glycol(PEG) by sol-gel method. The results showed that the addition of SiO2 to TiO2 thin films can suppress the grain growth of TiO2 crystal in the TiO2 thin films, low the contact angle for water of TiO2 films; the pore size is adjusted by adding different amount of PEG, the anatase TiO2 can grow on the porous Zn-SiO2/TiO2 composite thin films at 500 ℃; studies of photocatalytic degradation show that the degradation rate of porous Zn-SiO2/TiO2 composite thin films were higher than that of un-doped porous SiO2/TiO2 composite thin films.

  11. 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

  12. The domestication of ortho-quinone methides.

    Science.gov (United States)

    Bai, Wen-Ju; David, Jonathan G; Feng, Zhen-Gao; Weaver, Marisa G; Wu, Kun-Liang; Pettus, Thomas R R

    2014-12-16

    CONSPECTUS: An ortho-quinone methide (o-QM) is a highly reactive chemical motif harnessed by nature for a variety of purposes. Given its extraordinary reactivity and biological importance, it is surprising how few applications within organic synthesis exist. We speculate that their widespread use has been slowed by the complications that surround the preparation of their precursors, the harsh generation methods, and the omission of this stratagem from computer databases due to its ephemeral nature. About a decade ago, we discovered a mild anionic triggering procedure to generate transitory o-QMs at low temperature from readily available salicylaldehydes, particularly OBoc derivatives. This novel reaction cascade included both the o-QM formation and the subsequent consumption reaction. The overall transformation was initiated by the addition of the organometallic reagent, usually a Grignard reagent, which resulted in the formation of a benzyloxy alkoxide. Boc migration from the neighboring phenol produced a magnesium phenoxide that we supposed underwent β-elimination of the transferred Boc residue to form an o-QM for immediate further reactions. Moreover, the cascade proved controllable through careful manipulation of metallic and temperature levers so that it could be paused, stopped, or restarted at various intermediates and stages. This new level of domestication enabled us to deploy o-QMs for the first time in a range of applications including diastereocontrolled reactions. This sequence ultimately could be performed in either multipot or single pot processes. The subsequent reaction of the fleeting o-QM intermediates included the 1,4-conjugate additions that led to unbranched or branched ortho-alkyl substituted phenols and Diels-Alder reactions that provided 4-unsubstituted or 4-substituted benzopyrans and chroman ketals. The latter cycloadducts were obtained for the first time with outstanding diastereocontrol. In addition, the steric effects of the newly

  13. Mesostructured Hydrophobic-Oleophobic Silica Films for Sustained Functionality in Tribological Environments

    Science.gov (United States)

    Kessman, Aaron J.

    The primary goal of this research was to synthesize water- and oil-repellent coatings that offer sustained functionality and durability. Engineered low surface energy materials generally suffer from a lack of mechanical robustness, which makes them susceptible to damage by abrasive wear. Fluorinated silanes are often combined with alkoxide precursors via sol-gel co-condensation to create coatings with high hardness and good substrate adhesion. However, a common problem with these materials is that the organic moieties that provide low surface energy also become surface segregated and highly concentrated at the solid-air interface. With such a structure, mechanical removal of the top surface by abrasion, for example, reveals subsurface areas that are then much less concentrated in terms of functional chemistry. The material developed in this study was designed to overcome this problem by means of a tailored and templated mesostructure that effectively encapsulated the low surface energy functional moieties, and thus achieves sustained functionality during abrasive wear. This material, applied as a thin coating to a variety of substrates, has the potential to reduce waste and pollution and the environmental degradation of materials and structures. Improving the performance of such materials can benefit a wide variety of applications. These include optoelectronic devices including photovoltaic panels; automobile and aircraft; architectural structures; the chemical, food, and medical industries for hygienic and anti-fouling requirements; textiles; and household applications. This approach has further implications in areas such as boundary lubrication and drug delivery systems. Hydrophobic-oleophobic mesoporous fluorinated silica films were synthesized via sol-gel co-condensation and coated on glass substrates. Fluorosilane and surfactant template concentrations were varied to elucidate the effect of organic functionality and porosity on performance. Structural

  14. Protective performances of two anti-graffiti treatments towards sulfite and sulfate formation in SO{sub 2} polluted model environment

    Energy Technology Data Exchange (ETDEWEB)

    Carmona-Quiroga, Paula Maria, E-mail: paulacq@ietcc.csic.es [Eduardo Torroja Institute for Construction Science, Serrano Galvache 4 St, 28033 Madrid (Spain); Panas, Itai; Svensson, Jan-Erik; Johansson, Lars-Gunnar [Department of Chemistry and Biotechnology, Environmental Inorganic Chemistry, Chalmers University of Technology, S-41296 Goethenburg (Sweden); Blanco-Varela, Maria Teresa; Martinez-Ramirez, Sagrario [Eduardo Torroja Institute for Construction Science, Serrano Galvache 4 St, 28033 Madrid (Spain)

    2010-11-15

    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{sub 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{sub 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{sub 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{sub 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

  15. Atomic-Resolution Structures of Horse Liver Alcohol Dehydrogenase with NAD[superscript +] and Fluoroalcohols Define Strained Michaelis Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Plapp, Bryce V.; Ramaswamy, S. (inSTEM); (Iowa)

    2013-01-16

    Structures of horse liver alcohol dehydrogenase complexed with NAD{sup +} 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 {angstrom} resolution, providing estimates of atomic positions with overall errors of 0.02 {angstrom}, 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 {angstrom}. The oxygens of the alcohols are ligated to the catalytic zinc at a distance expected for a zinc alkoxide (1.96 {angstrom}) and participate in a low-barrier hydrogen bond (2.52 {angstrom}) 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{sup o} for C4N and 4.8{sup o} 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){sup +}. It appears that the nicotinamide ring is strained toward the transition state on the path to alcohol oxidation.

  16. Choosing the best molecular precursor to prepare Li4Ti5O12 by the sol-gel method using (1)H NMR: evidence of [Ti3(OEt)13](-) in solution.

    Science.gov (United States)

    García-Herbosa, Gabriel; Aparicio, Mario; Mosa, Jadra; Cuevas, José V; Torroba, Tomás

    2016-09-21

    (1)H NMR spectroscopy at 400 MHz in toluene-d8 of evaporated mixtures of lithium ethoxide and titanium(iv) isopropoxide in ethanol, used to prepare the spinel Li4Ti5O12 by the sol-gel method, may help clarify why the atomic ratio 5Li : 5Ti and not 4Li : 5Ti is the right choice to obtain the pure phase when performing hydrolysis at room temperature. The mixtures xLiOEt/yTi(OPr(i))4 in ethanol undergo alcohol exchange at room temperature, and the evaporated residues contain double lithium-titanium ethoxide [LiTi3(OEt)13] rather than simple mixtures of single metal alkoxides; this is of great relevance to truly understanding the chemistry and structural changes in the sol-gel process. Detailed inspection of the (1)H and (13)C VT NMR spectra of mixtures with different Li/Ti atomic ratios unequivocally shows the formation of [LiTi3(OEt)13] in a solution at low temperature. The methylene signals of free lithium ethoxide and Li[Ti3(OEt)13] coalesce at 20 °C when the atomic ratio is 5 : 5; however, the same coalescence is only observed above 60 °C when the atomic ratio is 4 : 5. We suggest that the highest chemical equivalence observed by (1)H NMR spectroscopy achieved through chemical exchange of ethoxide groups involves the highest microscopic structural homogeneity of the sol precursor and will lead to the best gel after hydrolysis. Variable temperature (1)H NMR spectra at 400 MHz of variable molar ratios of LiOEt/Ti(OPr(i))4 are discussed to understand the structural features of the sol precursor. While the precursor with the atomic ratio 5Li : 5Ti shows no signal of free LiOEt at 20 °C, both 4Li : 5Ti and 7Li : 5Ti show free LiOEt at 20 °C in their (1)H NMR spectra, indicating that the molar ratio 5Li : 5Ti gives the maximum rate of chemical exchange. DFT calculations have been performed to support the structure of the anion [Ti3(OEt)13](-) at room temperature.

  17. Diversification of ortho-Fused Cycloocta-2,5-dien-1-one Cores and Eight- to Six-Ring Conversion by σ Bond C-C Cleavage.

    Science.gov (United States)

    Eccleshare, Lee; Lozada-Rodríguez, Leticia; Cooper, Phillippa; Burroughs, Laurence; Ritchie, John; Lewis, William; Woodward, Simon

    2016-08-22

    Sequential treatment of 2-C6 H4 Br(CHO) with LiC≡CR(1) (R(1) =SiMe3 , tBu), nBuLi, CuBr⋅SMe2 and HC≡CCHClR(2) [R(2) =Ph, 4-CF3 Ph, 3-CNPh, 4-(MeO2 C)Ph] at -50 °C leads to formation of an intermediate carbanion (Z)-1,2-C6 H4 {CA (=O)C≡CB R(1) }{CH=CH(CH(-) )R(2) } (4). Low temperatures (-50 °C) favour attack at CB leading to kinetic formation of 6,8-bicycles containing non-classical C-carbanion enolates (5). Higher temperatures (-10 °C to ambient) and electron-deficient R(2) favour retro σ-bond C-C cleavage regenerating 4, which subsequently closes on CA providing 6,6-bicyclic alkoxides (6). Computational modelling (CBS-QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H(+) gave 1,2-dihydronaphthalen-1-ols, or under dehydrating conditions, 2-aryl-1-alkynylnaphthlenes. Enolates 5 react in situ with: H2 O, D2 O, I2 , allylbromide, S2 Me2 , CO2 and lead to the expected C-E derivatives (E=H, D, I, allyl, SMe, CO2 H) in 49-64 % yield directly from intermediate 5. The parents (E=H; R(1) =SiMe3 , tBu; R(2) =Ph) are versatile starting materials for NaBH4 and Grignard C=O additions, desilylation (when R(1) =SiMe) and oxime formation. The latter allows formation of 6,9-bicyclics via Beckmann rearrangement. The 6,8-ring iodides are suitable Suzuki precursors for Pd-catalysed C-C coupling (81-87 %), whereas the carboxylic acids readily form amides under T3P® conditions (71-95 %). PMID:27452351

  18. 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

  19. Synthesis and characterization of organic–inorganic hybrid materials prepared by sol–gel and containing Zn{sub x}Cd{sub 1−x}S nanoparticles prepared by a colloidal method

    Energy Technology Data Exchange (ETDEWEB)

    Gonçalves, Luis F.F.F., E-mail: luisf@quimica.uminho.pt [Centro de Química, Departamento de Química, Universidade do Minho, 4710-057 Braga (Portugal); Centro de Física, Departamento de Física, Universidade do Minho, 4710-057 Braga (Portugal); Silva, Carlos J.R. [Centro de Química, Departamento de Química, Universidade do Minho, 4710-057 Braga (Portugal); Kanodarwala, Fehmida K.; Stride, John A. [School of Chemistry, University of New South Wales, Sydney 2052 (Australia); Pereira, Mário R.; Gomes, Maria J.M. [Centro de Física, Departamento de Física, Universidade do Minho, 4710-057 Braga (Portugal)

    2013-12-15

    Nanocomposite materials based on a hybrid organic–inorganic ureasilicate matrix doped with Zn{sub x}Cd{sub 1−x}S nanoparticles were prepared. Zn{sub x}Cd{sub 1−x}S nanoparticles with different compositions (Zn/Cd mole ratio) were prepared through a colloidal method using reverse micelles. Previously to dispersion within the matrix precursors used to prepare the hybrid gel composite, the nanoparticles surface was modified in order to improve compatibility and stability with the matrix and to assure the preservation of the original optical properties of the nanoparticles. The matrix was obtained by the reaction between a silicon alkoxide modified by an isocyanate group and a di-amine functionalized oligopolyoxyethylene (Jeffamine ED-600), which by subsequent hydrolysis and condensation reactions formed a mechanically stable and highly transparent solid network containing the Zn{sub x}Cd{sub 1−x}S nanoparticles. The materials were characterized by absorption, steady-state and time-resolved photoluminescence spectroscopy and by HRTEM. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the nanoparticles within the matrix. The results obtained confirmed the preservation of the original optical properties of the nanoparticles after their incorporation into the ureasilicate matrix, showing that the developed method is suitable for the production of materials with potential applications in which it is necessary to take advantage of the optical properties of the nanoparticles incorporated. The HRTEM analysis confirmed that the dispersed nanoparticles show a high level of crystallinization. -- Highlights: • Synthesis of a hybrid ureasilicate matrix doped with Zn{sub x}Cd{sub 1−x}S nanoparticles. • The influence of the composition of the nanoparticles plays an important role in the optical properties of the nanocomposites. • Preservation of the optical properties of the nanoparticles associated with

  20. 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

  1. Pure and Y-substituted BaZrO3 ceramics. A possible support material for fabrication of YBa2Cu3O7-x high-Tc superconductors

    International Nuclear Information System (INIS)

    This thesis concerns the preparation and characterization of cuprate based high-Tc superconductors (Y-123 and Bi-2223) and especially development and testing of BaZrO3 based materials. The formation of YBa2Cu3Oy (Y-123) by a CO2-free route involving reaction sintering of stoichiometric mixtures of chemically prepared fine powders of Y2BaCuO5, BaCuO2 and CuO have been studied by thermal and XRD analysis. The synthesis and sintering of BaZrO3 powders prepared by the hydroxide-alkoxide-methanol sol-gel route have been studied. The phase relations in the system BaO-Y2O3-ZrO2 have been studied to determine the solid solubility limits for the perovskite phase BaXYYZrZON (X+X+Z=3) at 1500 deg. C. In the binary system Y2O3-BaZrO3 the solubility limit was found to be ≅19 mol% Y2O3, i.e. Ba0.81Y0.42Zr0.81O3. along the joint BaYO2.5-Ba the boundary was determined to be at BaY0.21Zr0.79O2.895. evidence for a new solid solution series between Ba3Y4O9 and ZrO2 are given, and a partial 1500 deg. C phase diagram for the ternary system BaO-Y2O3-ZrO2 is presented. The growth of BaZrO3 single crystals have been attempted both by a laser zone floating technique and flux methods. The compatibility between YBa2Cu3O7-X and BaZrO3, BaXYYZrZO3-δ as well as BaHfO3 have been studied at 950 deg. and 1050 deg. C. The results show the four most promising candidates as support materials for fabrication of YBa2Cu3Oy to be BaHfO3, BaY0.05Zr0.95O2.975, , BaZrO3 and BaY0.1Zr0.9O2.95. (EG)

  2. Mechanism of Alcohol-Water Dehydrogenative Coupling into Carboxylic Acid Using Milstein's Catalyst: A Detailed Investigation of the Outer-Sphere PES in the Reaction of Aldehydes with an Octahedral Ruthenium Hydroxide.

    Science.gov (United States)

    Hasanayn, Faraj; Al-Assi, Lara M; Moussawi, Rasha N; Omar, Boushra Srour

    2016-08-15

    In aqueous basic media, the square-pyramidal complex [Ru(PNN)(CO)(H)] (1-Ru, where PNN is a dearomatized bipyridyl-CH-P(t)Bu2 pincer ligand) catalyzes the transformation of alcohols and water into carboxylates and H2. A previous theoretical investigation reported the following mechanism for the reaction: (i) metal-catalyzed dehydrogenation of the alcohol into an aldehyde, (ii) metal-ligand cooperation (MLC) addition of water to 1-Ru to give an octahedral ruthenium hydroxide (2-Ru-OH), (iii) concerted MLC hydration of the aldehyde by 2-Ru-OH to give separated 1-Ru and a gem-diol, and (iv) concerted MLC dehydrogenation of the gem-diol by 1-Ru into an octahedral ruthenium dihydride (2-Ru-H) and a carboxylic acid. We calculate the outer-sphere PES in the reaction between the aldehyde and 2-Ru-OH to start with a localized coupling step yielding an ion-pair minimum (7-ip-OH) in which the hydroxyl group of an α-hydroxyl-alkoxide (gem-diolate) is coordinated to the metal of a cationic square-pyramidal complex. From 7-ip-OH, we identify a route to carboxylic acid that circumvents ligand deprotonation involving (i) 1,1-rearrangement of the gem-diolate within the contact ion pair through an α-OH/O(-) slippage TS into the octahedral 2-Ru-OCH(OH)R and (ii) a second 1,1-rearrangement through an α-O(-)/H slippage TS that gives a new ion-pair minimum in which the α-hydrogen of the anion is coordinated to the metal, followed by a localized hydride-transfer TS that gives a carboxylic acid and the octahedral hydride complex (2-Ru-H). The net transformation from 2-Ru-OH and the aldehyde to the carboxylic acid and 2-Ru-H can be viewed as a H/OH metathesis in which a hydride and a hydroxide are exchanged between the acyl group of the aldehyde and the metal center of 2-Ru-OH. The MLC mechanism gives the same metathesis products through the intermediacy of a gem-diol. When the SMD solvent continuum model is applied during geometry optimization with water as the solvent, the Gibbs free

  3. Formation mechanism and characteristics of lanthanum-doped BaTiO{sub 3} powders and ceramics prepared by the sol–gel process

    Energy Technology Data Exchange (ETDEWEB)

    Ianculescu, Adelina Carmen [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); Vasilescu, Catalina Andreea, E-mail: katyvasilescu85@yahoo.com [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); National Institute for Lasers, Plasma and Radiation Physics, P.O. Box MG54, 077125 Magurele (Romania); Crisan, Maria; Raileanu, Malina [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Vasile, Bogdan Stefan; Calugaru, Mihai [Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania); Crisan, Dorel; Dragan, Nicolae [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Curecheriu, Lavinia; Mitoseriu, Liliana [Department of Physics, Al. I. Cuza University of Iasi, Blvd. Carol I 11, 700506 Iasi (Romania)

    2015-08-15

    Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba{sub 1−x}La{sub x}TiO{sub 3}, for lower La concentrations (0 ≤ x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} for higher La concentration (x = 0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900 °C for 2 h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency. SEM investigations of the ceramics sintered at 1300 °C for 4 h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x ≤ 0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x = 0.025) are good dielectrics. The ceramic with x = 0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications. - Highlights: • Ba{sub 1−x}La{sub x}TiO{sub 3} (x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (x = 0.025) were prepared by sol–gel. • Ceramics with x < 0.5 exhibit semiconductor and high dielectric properties. • Ceramic with x = 0.025 exhibits acceptable low losses and diffuse phase transition.

  4. Waterless TiO{sub 2} atomic layer deposition using titanium tetrachloride and titanium tetraisopropoxide

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Virginia R.; Cavanagh, Andrew S.; Abdulagatov, Aziz I. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States); Gibbs, Zachary M. [Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309-0424 (United States); George, Steven M., E-mail: Steven.George@Colorado.Edu [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 and Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309-0427. (United States)

    2014-01-15

    The surface chemistry for TiO{sub 2} atomic layer deposition (ALD) typically utilizes water or other oxidants that can oxidize underlying substrates such as magnetic disks or semiconductors. To avoid this oxidation, waterless or oxidant-free surface chemistry can be used that involves titanium halides and titanium alkoxides. In this study, waterless TiO{sub 2} ALD was accomplished using titanium tetrachloride (TiCl{sub 4}) and titanium tetraisopropoxide (TTIP). In situ transmission Fourier transform infrared (FTIR) studies were employed to study the surface species and the reactions during waterless TiO{sub 2} ALD. At low temperatures between 125 and 225  °C, the FTIR absorbance spectra revealed that the isopropoxide species remained on the surface after TTIP exposures. The TiCl{sub 4} exposures then removed the isopropoxide species and deposited additional titanium species. At high temperatures between 250 and 300  °C, the isopropoxide species were converted to hydroxyl species by β-hydride elimination. The observation of propene gaseous reaction product by quadrupole mass spectrometry (QMS) confirmed the β-hydride elimination reaction pathway. The TiCl{sub 4} exposures then easily reacted with the hydroxyl species. QMS studies also observed the 2-chloropropane and HCl gaseous reaction products and monitored the self-limiting nature of the TTIP reaction. Additional studies examined the waterless TiO{sub 2} ALD growth at low and high temperature. Quartz crystal microbalance measurements observed growth rates of ∼3 ng/cm{sup 2} at a low temperature of 150  °C. Much higher growth rates of ∼15 ng/cm{sup 2} were measured at a higher temperature of 250  °C under similar reaction conditions. X-ray reflectivity analysis measured a growth rate of 0.55 ± 0.05 Å/cycle at 250  °C. X-ray photoelectron depth-profile studies showed that the TiO{sub 2} films contained low Cl concentrations <1 at. %. This waterless TiO{sub 2} ALD process

  5. Dispersion of impurities in pyrochlore/zirconolite-based ceramics

    International Nuclear Information System (INIS)

    Pyrochlore-rich and zirconolite-rich ceramics have been developed for the immobilization of excess weapons Pu. The ceramics are composed of a mixture of pyrochlore, zirconolite, brannerite and rutile. Impurity ions are present in most Pu-waste streams. Most of these impurities can be incorporated into the phases present in the ceramic; however some, such as B and Si, can promote the formation of additional phases. In this work, the impurity ions were classed into sets with supposedly the same valency (2+, 3+, 4+, 5+ and 6+). One set containing Np and Th and another set containing the glass formers (Al, Si, B, Na and K) were also made. These sets of elements were then added to a 'baseline' ceramics of nominal sintered composition, 95 wt.% pyrochlore (Ca0.89Gd0.22(Pu or Ce)0.22U0.44Hf0.23Ti2O7) and 5 wt.% HF-doped rutile, (Ti0.9Hf0.1O2). A sufficient amount of each of these sets of impurity ions was added so that the primary phases of the baseline ceramic were saturated with them and secondary phases formed. Both Pu/U-doped Ce/U-doped samples were made. The impurity elements were added as nitrates to an alkoxide-route precursor, which was calcined and then ball milled. Pellets were pressed from the powder and sintered in Ar, air or 3.7% H2 in Ar at about 1350 degrees Celsius for 4 hours. The obtained results are summarized in this work. As a matter of fact, most of the ions can be accommodated in the ceramic, but the partitioning across the different phases in the ceramic is not even. The groups will preferentially move to certain phases or, if sufficient amounts are present, result in the formation of new phases. The conclusion is that all ions of similar size and valency behave in a similar manner unless there are volatility problems

  6. Protective performances of two anti-graffiti treatments towards sulfite and sulfate formation in SO2 polluted model environment

    International Nuclear Information System (INIS)

    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 SO2 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 SO2 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 SO2 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 SO2 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

  7. 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

  8. Synthesis, characterization and solid-state photoluminescence studies of six alkoxy phenylene ethynylene dinuclear palladium(II) rods.

    Science.gov (United States)

    Figueira, João; Czardybon, Wojciech; Mesquita, José Carlos; Rodrigues, João; Lahoz, Fernando; Russo, Luca; Valkonen, Arto; Rissanen, Kari

    2015-03-01

    A rare family of six discrete binuclear [PdCl(PEt3)2] phenylene ethynylene rods with alkoxy side chains (methoxy, ethoxy and heptoxy) have been developed, and their solid-state photoluminescence results have been presented and discussed. The shorter bridging ligands are of the general formula H-C≡C-C6H2(R)2-C≡C-H, where R = H, OCH3, OC2H5, and OC7H15, whereas the longer ones are based on H-C≡C-C6H4-C≡C-C6H2(R)2-C≡C-C6H4-C≡C-H, where R = OCH3, OC2H5. These ligands display increasing length in both the main dimension (backbone length) as well as the number of carbons in the side chains (R, alkoxide side chain) that stem from the central phenylene moiety. The X-ray crystal structures of two of the prepared complexes are reported: one corresponds to a shorter rod, 1,4-bis[trans-(PEt3)2ClPd-C≡C]-2,5-diethoxybenzene (6c), while the second one is associated with a longer rod, the binuclear complex 1,4-bis[trans-(PEt3)2ClPd-4-(-C≡C-C6H4-C≡C)]-2,5-diethoxybenzene (7c). All new compounds were characterized by NMR spectroscopy ((1)H, (13)C{(1)H} and (31)P{(1)H}) as well as ESI-MS(TOF), EA, FTIR, UV-Vis, cyclic voltammetry and solid-state photoluminescence. Our work shows the influence of the alkoxy side chains on the electronic structure of the family of binuclear Pd rods by lowering its oxidation potential. In addition to this, the increase of the length of the bridge results in a higher oxidation potential. Solid state photoluminescence results indicate that Pd complexes are characterized by a marked decrease in both the emission intensity and the fluorescence lifetime values as compared to their ligands. This behaviour could be due to some degree of ligand-to-metal charge transfer.

  9. 在乙二醇甲醚溶液中合成NiTiO_3超细粉末%Synthesis of Nano-sized Particle Spinel NiTiO_3 by Electrolysis in Ethylene Glycol Methyl Ether Solution

    Institute of Scientific and Technical Information of China (English)

    王凤武; 徐迈; 魏亦军; 方文彦

    2011-01-01

    在无隔膜电解槽中,加入0.035mol/L(Bu4N)Br的乙二醇甲醚溶液,保持电解温度40℃、电流密度30mA/cm2时,先电解钛片6h,再电解镍片3h,制得镍、钛醇盐配合物,电流效率为95.1%。采用红外、拉曼光谱对其进行了表征。结果表明,前驱体结构为NiTi(OCH2CH2OCH3)6,可以有效克服团聚现象。水解、真空干燥24h后所得干凝胶在520℃煅烧2h制得纳米NiTiO3粉体。经X-射线衍射、电子透射显微镜测试表明,干凝胶粒径为20~30nm,钛酸镍NiTiO3粒径为25nm,纯度较高。%In a cell without separating the cathode and anode spaces,Ni and Ti alkoxide complex was synthesized by electrochemical dissolution of Ti for 6h,and of Ni for 3h at 40℃ in CH3OCH2CH2OH solution of 0.035mol/L(Bu4N)Br when current density is 30mA/cm2.The results of IR and Raman spectra showed that current efficiency reaches 95.1% and the precursor of NiTiO3is NiTi(OCH2CH2OCH3)6,which could prevent the precursor from gathering.The xerogel was obtained by dryness in vacuum for 24h and hydrolysis under pH≈9.0 of the precursor,which was heated at 520℃ for 2h to obtain the nano-NiTiO3 powder.XRD and SEM of nano-NiTiO3 suggested the average particle size of xerogel obtained was 20~30 nm and the nano-sized particle spinel NiTiO3was 25 nm with high purity.

  10. 在乙二醇甲醚溶液中合成前驱体水解法制备Zn2SnO4超细粉末%Preparation of nano-sized Zn2SnO4 spinel particle by electrolysis in CH3 OCH2 CH2 OH solution

    Institute of Scientific and Technical Information of China (English)

    朱传高; 王凤武; 徐迈; 方文彦

    2011-01-01

    Zinc and tin alkoxide was prepared in the without diaphragm cell when the tin sheet was electrolysed for 4 h and then zinc sheet was electrolysed for 4 h tetrabutylammonium (0. 15 mol/L)bromides were added to serve as supporting e-lectrolyte. Glycol and methyl ether were used as electrolyte. Current density in the 20 mA · cm -2 and temperature in the 30 ℃ were employed. The current efficiency was 90.3%. The structure of precursor was analyzed by Raman spectra,Infrared spectroscopy. The xerogel was prepared by vacuum drying for 24 h after hydrolyzing. The obtained xerogel were calcined at 450 ℃ for 2 h in air. Then, nanosized Zn, SnO4 were prepared successfully. The structural characterization of the xerogel and nano Zn2SnO4 was performed by X-ray diffraction (XRD) , transmission electron microscopy (TEM). The characterization results indicated that Zn2SnO4 nano-particles (size 25 - 35 nm) are obtained. The grain of xerogel was about20 - 30 nm. The product is high purity.%在无隔膜电解槽中,加入0.15 mol/L( Bu4N)Br的乙二醇甲醚溶液,保持电解温度30℃、电流密度20 mA.cm-2时,先电解锡片4h,再电解锌片4h,制得锌、锡醇盐配合物,电流效率为90.3%.采用红外、拉曼光谱对其进行了表征.结果表明,前驱体结构为Zn2 Sn( OCH2CH2OCH3)8,可以有效克服团聚现象.水解、真空干燥24 h后所得干凝胶在450℃煅烧2h制得纳米Zn2SnO4粉体.经X-射线衍射、电子透射显微镜测试表明,干凝胶粒径为20~30 nm,锡酸锌Zn2SnO4粒径在25~35 nm,纯度较高.

  11. Synthesis of Nano-sized Particle Spinel ZnTiO3 by Electrolysis in CH3OCH2CH2OH Solution%在乙二醇甲醚溶液中电解合成ZnTiO3超细粉末

    Institute of Scientific and Technical Information of China (English)

    朱传高; 王凤武; 徐迈; 方文彦

    2011-01-01

    在无隔膜电解槽中,加入0.035 mol·dm-3(Bu4 N)Br的乙二醇甲醚溶液,保持电解温度30℃、电流密度30mA·cm-2,先电解钛片6h,再电解锌片3h,制得锌、钛醇盐配合物ZnTi(OCH2CH2OCH3),,电流效率为95.4%.采用红外、拉曼光谱对其进行了表征.结果表明,前驱体中含有配体(OCH2CH2OCH3)6,可以有效克服团聚现象.水解后干燥24 h得到干凝胶,在450℃锻烧2h制得纳米ZnTiO3粉体.经X射线衍射、电子透射显微镜测试表明,干凝胶粒径为25 nm,钛酸锌粒径在20~30 nm,纯度较高.%Zinc and titanium alkoxide was prepared in the cell without diaphragm when the titanium sheet was electrolysed for 6 h and then zinc sheet was electrolysed for 3 h tetrabutylammonium (0.035 mol ·dm-3) bromides were added to serve as supporting electrolyte. Glycol and methyl ether were used as electrolyte. Current density of 30 A · dm-2 and temperature of 30 ℃ were employed. The current efficiency was 95.4%. The structure of precursor was analyzed by laser Raman spectra,infrared spectroscopy. The xerogel was prepared by vacuum drying for 24 h after hydrolyzi. The obtained xerogel were calcined at 450 ℃, 2 h in air. After 2 h, the nano ZnTiO3 were prepared successfully. The structural characterization of the xerogeld and nano ZnTiO3 was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM). The results indicated that ZnTiO3 nano-partieles (size 20-30 nm) are obtained. The grain of xerogel was about 25 nm. The product is high purity.

  12. 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.)

  13. Structure and properties of oxidative dehydrogenation catalysts based on MoO3/Al2O3

    International Nuclear Information System (INIS)

    a s the surface density increased, because all exposed surfaces in these samples reside within two-or three dimensional MoOx structures with similar reactivity. The ratio of rate constants for propane ODH and propane combustion reactions increased with increasing surface density and then remained constant for values above 5 Mo/nm2. These effects appear to reflect the tendency of A-O-Mo species to adsorb alkoxide intermediates and favor their sequential oxidation to COx. Propene combustion rate constants also decreased relative to those for propane ODH as two-dimensional structures form with increasing Mo surface density

  14. 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

  15. 室内装饰品负载氮掺杂氧化钛的光催化性能%Photocatalytic performance of nitrogen-doped titania coated on room decorations

    Institute of Scientific and Technical Information of China (English)

    王泽清; 郭薇; 辛钢; 吴丽琼; 马廷丽

    2011-01-01

    采用钛醇盐水解法与溶胶凝胶法,以氨水、尿素、三乙胺为氮源,制备了纳米TiO2-xNx光催化剂.为了在净化室内空气的同时能够装饰环境,提出了喷涂和浸泡2种工艺将光催化剂负载于室内装饰品,并在模拟太阳光的照射下对室内污染物甲醛进行降解.XRD、UV-Vis光谱及XPS分析结果表明,在烧结温度为400℃时得到的3种TiO 2-xNx是锐钛矿相,其中以尿素为氮源的TiO2-xNx温度达到600℃时开始发生相转变,3种TiO2xNx在可见光区域的400~550 nm均出现新的吸收;以氨水、尿素和三乙胺为氮源制备的TiO2xNx的掺氮量分别为2.77%、0.29%和0.47%.以氨水为氮源制备的光催化剂,14 h降解甲醛的效率达到了95%;以三乙胺为氮源制备的光催化剂7 h降解甲醛的效率达到了96%.因此,应用喷涂法在室内装饰品上负载光催化剂降解室内污染物具有很好的应用前景.%Nanocrystalline TiO2-xNx photocatalysts were prepared by hydrolysis of titanium alkoxide and sol-gel method using aqueous ammonia, urea and triethylamine as nitrogen sources, respectively. The photocatalytic activity of TiO2-xNx coated on the ornamental flowers by spray-coating and dipping methods was evaluated through a study of the decomposition of formaldehyde under simulated solar light. The obtained photocatalysts were characterized by X-ray diffraction, UV-Vis spectrum and X-ray photoelectron spectrum. The results show that three kinds of TiO2-xNx are mainly anatase phase after calcinations at 400℃. The TiO2-xNx prepared with urea was calcined under 600℃, the phase transformation was observed. Moreover, TiO2-xNx showed a new absorption from 400 to 550 nm in the visible light region. The XPS results show that the nitrogen content of TiO2-xNx using ammonia, urea and triethylamine as nitrogen sources was 2. 77% , 0. 29% and 0.47% , respectively.The degradation rate of formaldehyde reached 96% and 95% for the photocatalysts

  16. Theoretical study on the reaction mechanism of (CH3)3CO(.) radical with NO

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Hongmei; LIU; Kun; SUN; Chengke; LI; Zonghe

    2004-01-01

    [1]Sun, Z., Zheng, S. J., Wang, J. et al., First experimental observation on different ionic states of the tert-butoxy [(CH3)3CO' ] radical, Chem. Eur. J., 2001, 7(14): 2995-2999.[2]Wang, J., Sun, Z., Zhu, X. J. et al., First experimental observation on different ionic states of the CH3CH2O radical: a HeI photoelectron spectrum of the ethoxy CH3CH2O radical, Chem. Phys. Lett.,2001, 340: 98-102.[3]Zhu, X. J., Ge, M. F., Wang, J. et al., First experimental observation on different ionic states of both methylthio (CH3S') and methoxy (CH3O') radicals, Angew. Chem. Int. Ed., 2000, 39(11):1940-1943.[4]Ramond, T. M., Davico, G. E., Schwartz, R. L. et al., Vibronic structure of alkoxy radicals via photoelectron spectroscopy, J.Chem. Phys., 1999, 112: 1158-1169.[5]Blitz, M., Pilling, M. J., Robertson, S. H. et al., Direct studies on the decomposition of the tert-butoxy radical and its reaction with NO, Phys. Chem. Chem. Phys., 1999, 1: 73-80.[6]Lee, Y. Y., Wann, G., Lee, Y. P., Vibronic analysis of the A → X laser-induced fluorescence of jet-cooled methoxy (CH3O) radical,J. Chem. Phys., 1993, 99: 9465-9471.[7]Wiberg, K. B., Structures and charge distributions in alkoxide ions, J. Am. Chem. Soc., 1990, 112: 3379-3385.[8]Janousek, B. K., Zimmerman, A. H., Reed, K. J. et al., Electron photodetachment from aliphatic molecular anions, gas-phase electron affinities of methoxyl, tert-butoxyl, and neopentoxyl radicals, J. Am. Chem. Soc., 1978, 100: 6142-6148.[9]Griller, D., Ingold, K. U., Persistent carbon-centered radicals,Acc. Chem. Res., 1976, 9: 13-19.[10]Haire, D. L., Janzen, E. G., Synthesis and spin trapping kinetics of new alkyl substituted cyclic nitrones, Can. J. Chem., 1982, 60:1514-1522.[11]Walling, C., Kurkov, V. P., Positive halogen compounds, XV. Kinetics of the chlorination of Hydrocarbons by t-butyl hypochlorite,J. Am. Chem. Soc., 1967, 89: 4895-4901.[12]Becke, A. D., Density-functional thermochemistry, Ⅲ. The

  17. Synthesis and characterizations of novel polymer electrolytes

    Science.gov (United States)

    Chanthad, Chalathorn

    Polymer electrolytes are an important component of many electrochemical devices. The ability to control the structures, properties, and functions of polymer electrolytes remains a key subject for the development of next generation functional polymers. Taking advantage of synthetic strategies is a promising approach to achieve the desired chemical structures, morphologies, thermal, mechanical, and electrochemical properties. Therefore, the major goal of this thesis is to develop synthetic methods for of novel proton exchange membranes and ion conductive membranes. In Chapter 2, new classes of fluorinated polymer- polysilsesquioxane nanocomposites have been designed and synthesized. The synthetic method employed includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in-situ sol-gel condensation of the prepared triethoxylsilane-terminated fluorinated polymers with alkoxide precursors. The properties of the composite membranes have been studied as a function of the content and structure of the fillers. The proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases ion-exchange capacity and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane based nanocomposites. In Chapter 3, the synthesis of a new class of ionic liquid-containing triblock copolymers with fluoropolymer mid-block and imidazolium methacrylate

  18. 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

  19. Nanoconfinement Effects in Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kung, Harold [Northwestern Univ., Evanston, IL (United States)

    2016-09-19

    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 neighboring Sn-O-Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions. The open structure of the Sn center makes it accessible to larger molecules, including cellobiose which can be converted to 5-(hydroxymethyl)-furfural. The third structure is a support planted with functional group pairing of a known separation distance. Using a precursor molecule that contains a hydrolysable silyl ester bond, and making use of known chemistry to convert silanol groups into amino/pyridyl and phosphinyl groups, silica surfaces with carboxylic acid/silanol, carboxylic acid/amine, carboxylic acid/pyridine, and carboxylic acid/phosphine pairs can be constructed. The amino groups paired with carboxylic acid on such a surface is more active in the Henry reaction of 4-nitobenzaldehyde with nitromethane.

  20. 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.

  1. 耐高温核/壳结构TiO2/SiO2复合气凝胶的制备及其光催化性能%Preparation of Heat-Resistant, Core/Shell Nanostructured TiO2/SiO2 Composite Aerogels and Their Photocatalytic Properties

    Institute of Scientific and Technical Information of China (English)

    祖国庆; 沈军; 王文琴; 邹丽萍; 许维维; 张志华

    2015-01-01

    Core/shel nanostructured monolithic TiO2/SiO2 composite aerogels were prepared by the aniline-acetone in situ water formation sol-gel method. Titanium(IV) n-butoxide was used as a precursor fol owed by supercritical modification with partial y hydrolyzed titanium alkoxide and tetraethoxysilane during ethanol supercritical fluid drying. The obtained composite aerogel showed excel ent mechanical strength with a Young′s modulus of 4.5 MPa. The composite aerogel exhibited excel ent heat resistance. After heat treatment at 1000 °C its linear shrinkage decreased from 31%for the TiO2 aerogel to 10%for the composite aerogel. The specific surface area increased from 31 m2∙g-1 for the TiO2 aerogel to 143 m2∙g-1 for the composite aerogel. The composite aerogel exhibited excel ent photocatalytic performance during the degradation of methylene blue after heat treatment at 1000 °C. Its excel ent photocatalytic property is attributed to its high specific surface area and the smal particle size of the composite aerogel after heat treatment at 1000 ° C. The enhanced heat resistance, mechanical strength, and photocatalytic performance makes the obtained core/shel nanostructured TiO2/SiO2 composite aerogel a promising candidate for photocatalytic applications.%以钛酸四丁酯为源,采用苯胺-丙酮原位生成水溶胶-凝胶法,在乙醇超临界干燥过程中用部分水解的钛醇盐和硅醇盐对TiO2凝胶进行超临界修饰制备了具有核/壳纳米结构的块体TiO2/SiO2复合气凝胶.制备的复合气凝胶具有优异的机械性能,其杨氏模量可达4.5 MPa.复合气凝胶同时具有极好的高温热稳定性.经过1000°C热处理后,线性收缩由纯TiO2气凝胶的31%降至复合气凝胶的10%,且比表面积由纯TiO2气凝胶的31 m2∙g-1提升至复合气凝胶的143 m2∙g-1.此外,该复合气凝胶经1000°C热处理后具有优异的光催化降解亚甲基蓝的性能.其优异的光催化性能得益于TiO2/SiO2

  2. 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

  3. Designing for selectivity: weak interactions and the competition for reactive sites on gold catalysts.

    Science.gov (United States)

    Siler, C G F; Madix, R J; Friend, C M

    2016-07-01

    A major challenge in heterogeneous catalysis is controlling reaction selectivity, especially in complex environments. When more than one species is present in the gas mixture, the competition for binding sites on the surface of a catalyst is an important factor in determining reaction selectivity and activity. We establish an experimental hierarchy for the binding of a series of reaction intermediates on Au(111) and demonstrate that this hierarchy accounts for reaction selectivity on both the single crystal surface and under operating catalytic conditions at atmospheric pressure using a nanoporous Au catalyst. A partial set of measurements of relative binding has been measured by others on other catalyst materials, including Ag, Pd and metal oxide surfaces; a comparison demonstrates the generality of this concept and identifies differences in the trends. Theoretical calculations for a subset of reactants on Au(111) show that weak van der Waals interactions are key to predicting the hierarchy of binding strengths for alkoxides bound to Au(111). This hierarchy is key to the control of the selectivity for partial oxidation of alcohols to esters on both Au surfaces and under working catalytic conditions using nanoporous gold. The selectivity depends on the competition for active sites among key intermediates. New results probing the effect of fluorine substitution are also presented to extend the relation of reaction selectivity to the hierarchy of binding. Motivated by an interest in synthetic manipulation of fluorinated organics, we specifically investigated the influence of the -CF3 group on alcohol reactivity and selectivity. 2,2,2-Trifluoroethanol couples on O-covered Au(111) to yield CF3CH2O-C([double bond, length as m-dash]O)(CF3), but in the presence of methanol or ethanol it preferentially forms the respective 2,2,2-trifluoroethoxy-esters. The ester is not the dominant product in any of these cases, though, indicating that the rate of β-H elimination from

  4. 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

  5. Non-hydrolytic sol-gel synthesis and characterization of materials of the type AA'M3O12

    Science.gov (United States)

    Baiz, Tamam Issa

    In recent years, there has been an increased interest in negative thermal expansion (NTE) materials, which contract upon heating. Materials exhibiting this property have the potential for achieving better control of thermal expansion through the synthesis of composite materials with more desirable expansion coefficients. By introducing NTE materials into these composites, it is possible to offset the positive thermal expansion of other components in the composite. As a result, these NTE materials can find use in a wide range of applications such as optics, electronics, tooth fillings and any other area where exact positioning of parts over a wide range of temperatures is crucial. A family of materials that has been known to show NTE are A 2M3O12 compounds, where A can be a variety of trivalent cations and M can be Mo or W. Previous work on this system has shown that the thermal expansion is highly dependent on the type of trivalent cation employed. However, in spite of the interest in these A2M3O 12 compounds, little research has been dedicated to synthesizing materials containing two aliovalent cations instead of just one or two trivalent cations. In fact, the first example of a heterosystem with +2 and +4 cations was not reported until 2004. This dissertation presents results of investigation and characterization of these mixed cation systems, and the change in the thermal expansion properties. The first goal of the research presented herein was to synthesize mixed cation systems using a lower temperature route, and then compare the materials synthesized using low temperature methods with those synthesized using the ball-milling method. This will ensure the validity of applying a lower temperature method to these mixed cation systems. A non-hydrolytic sol-gel (NHSG) method was used, which is based on the reaction of metal alkoxides with metal halides to form M-O-M linkages, with alkyl halides as byproducts. With this method, MgHfW3O12 and MgZrW3O 12 were

  6. 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.