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1

A novel non-aqueous sol-gel route for the in situ synthesis of high loaded silica-rubber nanocomposites.  

PubMed

Silica-natural rubber nanocomposites were obtained through a novel non-aqueous in situ sol-gel synthesis, producing the amount of water necessary to induce the hydrolysis and condensation of a tetraethoxysilane precursor by esterification of formic acid with ethanol. The method allows the synthesis of low hydrophilic silica nanoparticles with ethoxy groups linked to the silica surface which enable the filler to be more dispersible in the hydrophobic rubber. Thus, high loaded silica composites (75 phr, parts per hundred rubber) were obtained without using any coupling agent. Transmission Electron Microscopy (TEM) showed that the silica nanoparticles are surrounded by rubber layers, which lower the direct interparticle contact in the filler-filler interaction. At the lowest silica loading (up to 30 phr) silica particles are isolated in rubber and only at a large amount of filler (>60 phr) the interparticle distances decrease and a continuous percolative network, connected by thin polymer films, forms throughout the matrix. The dynamic-mechanical properties confirm that the strong reinforcement of the rubber composites is related to the network formation at high loading. Both the improvement of the particle dispersion and the enhancement of the silica loading are peculiar to the non-aqueous synthesis approach, making the method potentially interesting for the production of high-loaded silica-polymer nanocomposites. PMID:24651692

Wahba, Laura; D'Arienzo, Massimiliano; Dirè, Sandra; Donetti, Raffaella; Hanel, Thomas; Morazzoni, Franca; Niederberger, Markus; Santo, Nadia; Tadiello, Luciano; Scotti, Roberto

2014-04-01

2

Oxalate based non-aqueous sol-gel synthesis of phase pure sub-micron LiFePO{sub 4}  

SciTech Connect

We report on the synthesis and preliminary characterisation by X-ray diffraction (XRD), scanning electron microscopy (SEM), Moessbauer spectroscopy and infrared spectroscopy (IR) of C-LiFePO{sub 4}. Homogeneous sub-micron sized particles of surface carbon coated phase pure LiFePO{sub 4} are synthesised by a novel non-aqueous oxalate based sol-gel procedure. Our synthetic route successfully overcomes the incidence of Fe{sup 3+}, effectively controls undesirable particle growth and has the potential for upscaling and application as Li-ion battery cathodes.

Sundarayya, Y. [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Kumara Swamy, K.C. [School of Chemistry, University of Hyderabad, Hyderabad 500046 (India); Sunandana, C.S. [School of Physics, University of Hyderabad, Hyderabad 500046 (India)], E-mail: csssp@uohyd.ernet.in

2007-11-06

3

Synthesis of Carbon Nanotubes Using Sol Gel Route  

NASA Astrophysics Data System (ADS)

Since 1990, carbon nanotubes were discovered and they have been the object of intense scientific study ever since. A carbon nanotube is a honeycomb lattice rolled into a cylinder. The diameter of a carbon nanotube is of nanometer size and the length is in the range of micrometer. Many of the extraordinary properties attributed to nanotubes, such as tensile strength and thermal stability, have inspired predictions of microscopic robots, dent-resistant car bodies and earthquake-resistant buildings. The first products to use nanotubes were electrical. Some General Motors cars already include plastic parts to which nanotubes were added; such plastic can be electrified during painting so that the paint will stick more readily. Two nanotube-based lighting and display products are well on their way to market. In the long term, perhaps the most valuable applications will take further advantage of nanotubes' unique electronic properties. Carbon nanotubes can in principle play the same role as silicon does in electronic circuits, but at a molecular scale where silicon and other standard semiconductors cease to work. There are several routes to synthesize carbon nanotubes; laser vaporization, carbon arc and vapor growth. We have applied a different route using sol gel chemistry to obtain carbon nanotubes. This work is patent-pending.

Abdel-Fattah, Tarek

2002-12-01

4

Sol-gel route to the tunneled manganese oxide cryptomelane  

SciTech Connect

The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the loss of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.

Ching, S.; Roark, J.L. [Connecticut College, New London, CT (United States)] [Connecticut College, New London, CT (United States); Duan, N.; Suib, S.L. [Univ. of Connecticut, Storr, CT (United States)] [Univ. of Connecticut, Storr, CT (United States)

1997-03-01

5

YTTRIUM ALUMINATE CERAMIC FIBERS VIA PRE-CERAMIC POLYMER AND SOL-GEL ROUTES  

Microsoft Academic Search

Yttrium aluminum garnet (YAG - Y3Al5O12) fibers have been prepared by dry spinning solutions of yttrium and aluminum carboxylate polymers (precursor route) and by dry spinning aqueous oxide sols (sol-gel route). Fibers from aqueous diphasic gels are prepared by mixing a colloidal alumina sol containing 50-nm hydrous alumina with a colloidal yttria sol containing 10-nm yttrium oxide, using polyvinylpyrrolidone as

BRUCE KING; YIN LIU; SURESH BASKARAN; RICHARD LAINE; JOHN HALLORAN

1992-01-01

6

Preparation of LiTaO 3 nanoparticles by a sol–gel route  

Microsoft Academic Search

A sol–gel route was developed to prepare pure ultrafine LiTaO3 powders using Ta2O5, Li2CO3, citric acid (CA) as chelating agent, ethylene glycol (EG) as esterification agent and polyethylene glycol (PEG) as dispersant.\\u000a The effects of pH value and heat treatment temperature of powder precursor on the synthesis of LiTaO3 powders were investigated. The phase content and morphology of the final

Y. G. Liu; J. H. Hu; Z. H. Huang; M. H. Fang

2011-01-01

7

Synthesis of Sol-Gel Matrices for Encapsulation of Enzymes Using an Aqueous Route  

SciTech Connect

Sol-gel matrices are promising host materials for potential chemical and biosensor applications. Previous studies have focused on modified sol-gel routes using alkoxides for encapsulation of enzymes. However the formation of alcohol as a byproduct during hydrolysis and condensation reactions poses limitations. We report the immobilization of glucose oxidase and peroxidase in silica prepared by an aqueous route which may provide a more favorable environment for the biomolecules. A two step aqueous sol-gel procedure using sodium silicate as the precursor was developed to encapsulate the enzymes and the dye precursor, o-dianisidine. Glucose oxidase catalyzes the oxidation of glucose to give gluconic acid and hydrogen peroxide. Peroxidase then catalyzes the reaction of the dye precursor with hydrogen peroxide to produce a colored product. The kinetics of the coupled enzymatic reactions were monitored by optical spectroscopy and compared to those occurring in tetramethyl orthosilicate (TMOS) derived silica matrices developed by Yamanaka. Enhanced kinetics in the aqueous silicate matrices were related to differences in the host microstructure as elucidated by microstructural comparisons of the corresponding aerogels.

Ashley, C.S.; Bhatia, R.B.; Brinker, C.J.; Harris, T.M.

1998-11-23

8

Aluminium-doped zinc oxide films prepared by an inorganic sol–gel route  

Microsoft Academic Search

Thin films of aluminium-doped zinc oxide have been formed on glass using an inorganic sol–gel route and the dip-coating process. The films were formed by the thermal decomposition of a stable precursor colloidal sol prepared by an ethanolic reflux of Zn(CH3COO)2·2H2O and Al(NO3)3·9H2O. Lactic acid was used as hydrolysis catalyst and acetylacetone and diethanolamine were added to improve film homogeneity.

Rodrigo F. Silva; Maria E. D. Zaniquelli

2004-01-01

9

Synthesis and characterization of (Zn, Mn)TiO 3 by modified sol–gel route  

Microsoft Academic Search

Hexagonal ilmenite-type (Zn1?xMnx)TiO3 (0?x?0.9) ceramic powders were synthesized by a sol–gel route including the Pechini process with heat treatments at 600°C for 3h and 800°C for 6h. The thermal stability of ZnTiO3 dielectric ceramics was improved (>1200°C) by doping manganese. The dielectric constant of (Zn1?xMnx)TiO3 ceramic was higher than those of (Zn, M)TiO3 (M=Co, Ni, etc.), increased with the amount

Mingzhen Zheng; Xianran Xing; Jinxia Deng; Lu Li; Jie Zhao; Lijie Qiao; Chunying Fang

2008-01-01

10

Routes to extrinsic and intrinsic self-healing corrosion protective sol-gel coatings: a review  

NASA Astrophysics Data System (ADS)

Sol-gel pre-treatments and coatings are an important class of passive protective coatings, which can effectively prevent corrosion of various metallic substrates through adhesion improvement and barrier protection. Recently, sol-gel chemistry has been proposed as an appropriate method for implementation of self-healing functionality in coatings via extrinsic concepts. In this review we will analyze the most relevant existing works on self-healing sol-gel coatings, including new work done in the direction of implementing intrinsic healing capabilities to sol-gels. The development of active sol-gel coatings is due to the broad chemical versatility of precursors and low processing temperature of this type of chemistry.

Abdolah Zadeh, M.; van der Zwaag, S.; Garcia, S. J.

2013-06-01

11

Effects of a Protic Ionic Liquid on the Reaction Pathway during Non-Aqueous Sol-Gel Synthesis of Silica: A Raman Spectroscopic Investigation  

PubMed Central

The reaction pathway during the formation of silica via a two-component “non-aqueou” sol-gel synthesis is studied by in situ time-resolved Raman spectroscopy. This synthetic route is followed with and without the addition of the protic ionic liquid 1-ethylimidazolium bis(trifluoromethanesulfonyl)imide (C2HImTFSI) in order to investigate its effect on the reaction pathway. We demonstrate that Raman spectroscopy is suitable to discriminate between different silica intermediates, which are produced and consumed at different rates with respect to the point of gelation. We find that half-way to gelation monomers and shorter chains are the most abundant silica species, while the formation of silica rings strongly correlates to the sol-to-gel transition. Thus, curling up of linear chains is here proposed as a plausible mechanism for the formation of small rings. These in turn act as nucleation sites for the condensation of larger rings and thus the formation of the open and polymeric silica network. We find that the protic ionic liquid does not change the reaction pathway per se, but accelerates the cyclization process, intermediated by the faster inclusion of monomeric species. PMID:24743891

Martinelli, Anna

2014-01-01

12

Effects of PVA content on the synthesis of LaFeO 3 via sol–gel route  

Microsoft Academic Search

LaFeO3 were synthesized via a sol–gel route based on polyvinyl alcohol (PVA). Differential scanning calorimetry (DSC), Thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) techniques were used to characterize precursors and derived oxide powders. The effect of the ratios of positively charged valences to hydroxyl groups of PVA (Mn+\\/–OH)

Jiansheng Feng; Ting Liu; Yebin Xu; Jingyuan Zhao; Yanyan He

2011-01-01

13

Preparation and characterization of Ln2Zr2O7 microspheres by an inorganic sol-gel route  

Microsoft Academic Search

Free-flowing Ln2Zr2O7 microspheres (Ln=lanthanide) were prepared by an aqueous inorganic sol-gel route without any intermediate phase formation. The gel spheres obtained at room temperature were shown by X-ray diffraction to be amorphous but calcination to 750 °C produced fully crystalline fluorite phases. On calcination to 850 °C, pyrochlore phases were formed with suitable lanthanides. The microspheres were characterized by X-ray

A. K. Bhattacharya; A. Hartridge; K. K. Mallick; J. L. Woodhead

1994-01-01

14

Preparation of a mesoporous silicon boron nitride via a non-aqueous sol-gel route.  

PubMed

A silicon boron imide based gel Si3B(NH)x(NH2)y(NMe2)z was prepared via catalytic ammonolysis of tris[tris(dimethylamino)silylamino]boron B[HNSi[N(CH3)2]3]3; pyrolysis of the gel under ammonia at 1,000 degrees C gives a mesoporous silicon boron nitride with high surface area and narrow pore size distribution. PMID:12585411

Cheng, Fei; Toury, Berangere; Lefebvre, Frédéric; Bradley, John S

2003-01-21

15

Low temperature synthesis of aluminium titanate by an aqueous sol–gel route  

Microsoft Academic Search

Formation of aluminium titanate (AT) has been achieved at low temperature through sol–gel process using boehmite and titanium hydroxide as precursors by controlling the particle size at nanoscale followed by in-situ peptisation. The formations of AT phase, particle size distributions, sintering and thermal expansion characteristics, and microstructural features have been reported. DTA and XRD analysis have been performed to confirm

M. Jayasankar; S. Ananthakumar; P. Mukundan; K. G. K. Warrier

2007-01-01

16

Production and characterization of spodumene dosimetric pellets prepared by a sol-gel route  

NASA Astrophysics Data System (ADS)

Spodumene is an aluminosilicate that has shown good results for high-dose TL dosimetry for beta or gamma rays. Due to its chemical composition (LiAlSi2O6) it has potential to be used as a neutron dosimeter. The synthetic spodumene is usually produced by solid state reaction and conventional sol-gel, whose shortcomings arise from the need to employ high temperatures and high cost reagents, respectively. Proteic sol-gel method is promising, because it can reduce production costs and the possibility of environmental contamination. This work reports the production of the spodumene by the proteic sol-gel method using edible unflavored gelatin as a precursor. The product is characterized physically and morphologically, and investigated its applicability as a TL dosimeter. Two sets of samples were prepared using different sources of silicon, one with TEOS (Si(OC3H5)4) and one with SILICA (SiO2). The materials produced were characterized by X-ray diffraction, differential thermal analysis and thermogravimetry in order to evaluate the structural properties, as well as possible changes in physical or chemical properties depending on the temperature. The production of spodumene was successful, with generation of the crystals in the ?-phase with tetragonal structure. Sintered pellets produced from these crystals were irradiated with a 90Sr-90Y source and their TL glow curves were evaluated. Although the samples prepared by the proteic sol-gel method with TEOS presented a lower forming temperature, the samples produced with SILICA showed higher sensitivity to radiation.

Lima, H. R. B. R.; Nascimento, D. S.; Bispo, G. F. C.; Teixeira, V. C.; Valério, M. E. G.; Souza, S. O.

2014-11-01

17

Preparation and nonlinear optical properties of indium nanocrystals in sodium borosilicate glass by the sol–gel route  

SciTech Connect

Graphical abstract: The sodium borosilicate glass doped with indium nanocrystals have been successfully prepared by sol–gel methods. And the indium nanocrystals in tetragonal crystal system have formed uniformly in the glass, and the average diameter of indium nanocrystals is about 30 nm. The third-order optical nonlinear refractive index ?, absorption coefficient ?, and susceptibility ?{sup (3)} of the glass are determined to be ?4.77 × 10{sup ?16} m{sup 2}/W, 2.67 × 10{sup ?9} m/W, and 2.81 × 10{sup ?10} esu, respectively. Highlights: ? Indium nanocrystals embedded in glass matrix have been prepared by sol–gel route. ? The crystal structure and composition are investigated by XRD and XPS. ? Size and distribution of indium nanocrystals is determined by TEM. ? The third-order optical nonlinearity is investigated by using Z-scan technique. -- Abstract: The sodium borosilicate glass doped with indium nanocrystals have been successfully prepared by sol–gel route. The thermal stability behavior of the stiff gel is investigated by thermogravimetric (TG) and differential thermal (DTA) analysis. The crystal structure of the glass is characterized by X-ray powder diffraction (XRD). Particle composition is determined by X-ray photoelectron spectroscopy (XPS). Size and distribution of the nanocrystals are characterized by transmission electron microscopy (TEM) as well as high-resolution transmission electron microscopy (HRTEM). Results show that the indium nanocrystals in tetragonal crystal structure have formed in glass, and the average diameter is about 30 nm. Further, the glass is measured by Z-scan technique to investigate the nonlinear optical (NLO) properties. The third-order NLO coefficient ?{sup (3)} of the glass is determined to be 2.81 × 10{sup ?10} esu. The glass with large third-order NLO coefficient is promising materials for applications in optical devices.

Zhong, Jiasong [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)] [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China) [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhao, Haijun; Chen, Zhaoping [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)] [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Liang, Xiaojuan [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)] [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhao, Wenguang; Chen, Guoxin [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)] [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2012-11-15

18

Comparative study of sol gel-hydrothermal and sol gel synthesis of titania silica composite nanoparticles  

NASA Astrophysics Data System (ADS)

Titania-silica composite nanoparticles were prepared by sol-gel-hydrothermal and sol-gel routes, respectively, and their physico-chemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol-gel-hydrothermal route led to anatase titania-silica composite nanoparticles with large specific surface area, but the sol-gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol-gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol-gel route. On the basis of XRD, FT-IR, XPS and 29Si MAS-NMR, a strong interaction was found between SiO 2 and TiO 2, and Ti-O-Si bonds formed during both the two routes. But more Ti-O-Si bonds formed in the composite nanoparticles prepared by sol-gel-hydrothermal route than those prepared by sol-gel route. As a result, the titania-silica composite nanoparticles prepared by sol-gel-hydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol-gel route, and it had excellent photocatalytic activity even after calcined at 1000 °C.

Li, Zhijie; Hou, Bo; Xu, Yao; Wu, Dong; Sun, Yuhan; Hu, Wei; Deng, Feng

2005-05-01

19

Aluminosilicates with varying alumina-silica ratios: synthesis via a hybrid sol-gel route and structural characterisation.  

PubMed

Aluminosilicates with varying Al(2)O(3):SiO(2) molar ratios (3 : 1, 3 : 2, 3 : 3 and 3 : 4) have been synthesized using a hybrid sol-gel route using boehmite sol as the precursor for alumina and tetraethyl orthosilicate (TEOS) as the precursor for silica. The synthesis of boehmite sol from aluminium nitrate, and its use as the alumina precursor, is cost effective compared to alkoxide precursors. Structural aspects, including bonding and coordination, are studied in detail for samples calcined in the temperature range 400-1400 degrees C using both NMR and FTIR spectroscopy: the results are correlated with phase formation data (spinel and high temperature phases) obtained from XRD and thermal analysis. FTIR results show a broadening of peaks at 800 degrees C indicating a disordered distribution of octahedral sites caused by crosslinking between AlO(6) octahedral and SiO(4) tetrahedral units prior to the formation of mullite. (27)Al MAS NMR spectra are consistent with a progressive decrease in the number of AlO(6) polyhedra with increasing temperature corresponding to Al in these units being forced to adopt a tetrahedral coordination due to the increasing presence of similarly coordinated Si species. XRD results confirm the formation of pure mullite at 1250 degrees C for a 3Al(2)O(3):2SiO(2) system. At 1400 degrees C, phase pure mullite is observed for all compositions except 3Al(2)O(3):SiO(2) where alpha-Al(2)O(3) is the major phase with traces of mullite. The synthesis of aluminosilicates through a hybrid sol-gel route and the detailed insight into structural features gained from spectroscopic and diffraction techniques contributes further to the development of these materials in applications ranging from nanocatalysts to high-temperature ceramics. PMID:20411190

Nampi, Padmaja Parameswaran; Moothetty, Padmanabhan; Berry, Frank John; Mortimer, Michael; Warrier, Krishna Gopakumar

2010-04-21

20

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

SciTech Connect

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.

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

2005-02-11

21

Nanocrystalline Er-doped SnO2 prepared by sol-gel route  

NASA Astrophysics Data System (ADS)

Much research has been attracted to search for great host materials that can optimize the luminescent efficiency of Er3+ ions in applications such as photonic devices. Due to its interesting physical, chemical and optical properties, special attention has been focused on SnO2 which has wide band gap and high visible range transparency that make SnO2 an attractive host for Er3+ ions. However, it is very important that the Er3+ ions incorporated be well dispersed in the SnO2 matrix in order to get high efficiency in luminescence properties. The degree of dispersion of Er3+ ions in a matrix is closely related to the crystallite size of the matrix as well as the ratio of Er3+ to SnO2 which must be identified to obtain the crystallite size in a suitable practical range. In this study nano-size Er3+-doped SnO2 has been synthesized by the sol-gel method. Increasing amounts Er3+ ions were added to ethanolic solutions of SnCl4.5H2O and let dry at 80°C. Phase changes of samples heated at various temperatures were monitored using x-ray diffraction (XRD) and the nanocrystallinity was determined by Scherrer's equation. The surface morphology was investigated by using SEM. XRD pattern of undoped SnO2 showed crystallization of tetragonal rutile SnO2 increased as the temperature of heat treatment was increased and the crystallization appeared to be complete after 2 hours heat treatment at 600°C. XRD of samples doped with Er3+ ions did not, however, depict obvious difference. SEM images showed the presence of aggregates of very small individual particles (˜0.2nm). The grain size of the SnO2 varied according to the heat treatment temperature and the concentration of Er3+ ions incorporated.

Zulfadly, M. A. M.; Kamil, A. R. M.; Jais, U. Sarah

2012-06-01

22

Physical properties of NxTiO2 prepared by sol-gel route  

NASA Astrophysics Data System (ADS)

The compounds NxTiO2(x=0, 0.05, 0.1, 0.2) with the anatase structure have been synthesized by Sol-Gel method using Tri-ethyl Amine as nitrogen source and their optical, electrical and electrochemical properties are investigated. The electrical conductivity and thermoelectric power are measured in the temperature rang 300-600 K. The samples exhibit p-type behavior in contrast to TiO2. The doped-samples exhibit two optical transitions (2.35?Eh-Vis(eV)?2.55; 1.97?El-Vis (eV)?2.06) directly allowed in the visible region, while only one transition is observed in UV region (EUV?3.00 eV). Pure TiO2 shows direct band gap transition of 3.17 eV. The results confirm experimentally the calculations of Di. Valentin et al. [42]. The transitions Eh-Vis and El-Vis are attributed respectively to the promotion of electrons from the localized N 2p and ?* N-O bond to the conduction band. In all cases, EUV is associated to the forbidden band energy. Though that the conductivity is generally improved by doping process, only N0.05TiO2 and N0.1TiO2 shows an enhanced mobility. The mechanism of conduction takes place by small polaron hopping. The band edge positions of NxTiO2 (x=0, 0.05, 0.1, 0.2) at room temperature is predicted from the obtained physical properties. This study proves experimentally the principal role of nitrogen in doping process and permits the electronic states localization associated with N-impurities in TiO2 anatase.

Brahimi, Razika; Bessekhouad, Yassine; Trari, Mohamed

2012-09-01

23

The morphology, proliferation rate, and population doubling time factor of adipose-derived mesenchymal stem cells cultured on to non-aqueous SiO2, TiO2, and hybrid sol-gel-derived oxide coatings.  

PubMed

In recent years, much attention has been paid to the development of tissue engineering and regenerative medicine, especially when stem cells of various sources are concerned. In addition to the interest in mesenchymal stem cells isolated from bone marrow, recently more consideration has been given to stem cells isolated from adipose tissue (AdMSCs), due to their less invasive method of collection as well as their ease of isolation and culture. However, the development of regenerative medicine requires both the application of biocompatible material and the stem cells to accelerate the regeneration. In this study, we investigated the morphology, proliferation rate index (PRi), and population doubling time factor of adipose-derived mesenchymal stem cells cultured on non-aqueous sol-gel-derived SiO2, TiO2, and SiO2/TiO2 oxide coatings. The results indicated an increase in PRi of AdMSCs when cultured on to titanium dioxide, suggesting its high attractiveness for AdMSCs. In addition, the proper morphology and the shortest doubling time of AdMSCs were observed when cultured on titanium dioxide coating. PMID:24408867

Marycz, Krzysztof; Krzak-Ro?, Justyna; Donesz-Sikorska, Anna; ?mieszek, Agnieszka

2014-11-01

24

Low temperature nanostructured zinc titanate by an aqueous particulate sol–gel route: Optimisation of heat treatment condition based on Zn:Ti molar ratio  

Microsoft Academic Search

Nanocrystalline zinc titanate (ZnTiO3) thin films and powders with purity of 94% were produced at the low sintering temperature of 500°C and the short sintering time of 1h by a straightforward aqueous particulate sol–gel route. The effect of Zn:Ti molar ratio was studied on the crystallisation behaviour of zinc titanates. The prepared sols showed a narrow particle size distribution in

M. R. Mohammadi; D. J. Fray

2010-01-01

25

Novel nonhydrolytic sol-gel route to low-OH- and CH-containing organic-inorganic composites  

NASA Astrophysics Data System (ADS)

A new synthesis route to organic-inorganic composites with low OH- and CH-content has been developed. Thus methacrylate- modified chlorosilanes were either homocondensed or cocondensed with fluoroalkyl-modified chlorosilanes by a non- hydrolytic reaction with 2-methyl-2-propanol under formation of an inorganic network and hydrogen chloride and tertiary butyl chloride as well. Remaining chlorosilane groups were reacted by a second alcohol treatment to obtain air-stable, highly condensed, and low OH-containing sols. The condensation was followed by 29Si-NMR-spectroscopy, showing T2- content of up to 60% and T3 content of up to 35% for trichlorosilanes and D2-content of more than 90% for dichlorosilanes respectively. The OH-content, which was estimated by FT-IR-spectroscopy, was lower than 10% referring to materials prepared by the conventional aqueous sol-gel process. For further decrease of the CH-content copolymerization with fluorinated methacrylates was investigated. After addition of a photoinitiator transparent bulk materials with a diameter of 1 cm and a length of 1.5 cm were obtained by photopolymerization in closed UV-transparent containers using a Beltronr UV apparatus with a low pressure Hg-Xe lamp. NIR-absorbance measurements were carried out and optical losses of bulk materials were determined. Cocondensed and copolymerized materials show low optical losses of 0.12 dB/cm at 1300 nm and 0.33 dB/cm at 1550 nm.

Mennig, Martin; Zahnhausen, Michael; Schmidt, Helmut K.

1998-07-01

26

Advances in sol-gel coating technologies  

SciTech Connect

Sol-gel coatings are thin, oxide layers applied from aqueous and non-aqueous media. In a dipping operation, the layer is typically less than one micron thick. This approach to depositing oxide layers has been used primarily in optical and electronic applications. Uses of these coatings in areas of wear and corrosion are known only in a few cases, such as semiconductor passivation layers or infiltrated fiber composites. The prospects for using sol-gel coatings for wear and corrosion are improving with new studies of electrochemical infiltration of gel layers and organic/inorganic hybrid layers. 57 refs., 6 figs., 2 tabs.

Klein, L.C. [Rutgers-The State Univ., Piscataway, NJ (United States). Ceramics Dept.; Sheppard, K. [Stevens Inst. of Technology, Hoboken, NJ (United States)

1995-12-31

27

Thin Films Derived by a Particulate Sol-Gel Route with Various Cr:Ti Molar Ratios  

NASA Astrophysics Data System (ADS)

Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature and Cr:Ti molar ratio. Furthermore, it was found that Cr2O3 retarded the anatase to rutile transformation up to 800°C. The activation energy of crystallite growth was calculated to be in the range of 1.3 kJ/mol to 2.9 kJ/mol. Transmission electron microscopy (TEM) imaging showed that one of the smallest crystallite sizes was obtained for TiO2-Cr2O3 binary mixed oxide, being 5 nm at 500°C. Field-emission scanning electron microscopy (FESEM) analysis revealed that the deposited thin films had nanostructured morphology with average grain size in the range of 20 nm to 40 nm at 500°C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of NO2 gas at low operating temperature of 200°C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, calibration curves revealed that TiO2-Cr2O3 sensors followed the power law (where S is the sensor response, the coefficients A and B are constants, and [gas] is the gas concentration) for two types of gas, exhibiting excellent capability for detection of low gas concentrations.

Mohammadi, M. R.; Fray, D. J.

2014-11-01

28

Fabrication of PbS Nanoparticles Embedded in Silica Gel by Reverse Micelles and Sol-Gel Routes  

Microsoft Academic Search

PbS doped-silica gels showing a visible absorption onset were prepared by the sol-gel method. PbS nanoparticles with strong quantum-confinement effect were obtained from sodium sulfide and lead nitrate by the reverse micelle method. Chemical parameters such as the water\\/surfactant and the [Pb2+]\\/[S2-] ratios play a very important role in the PbS particle size and in their absorption threshold. The PbS

N. Pellegri; R. Trbojevich; O. de Sanctis; K. Kadono

1997-01-01

29

Enzymatic hydrolysis of biomass with recyclable use of cellobiase enzyme immobilized in sol–gel routed mesoporous silica  

Microsoft Academic Search

In this work, a new immobilized cellobiase enzyme system was used in the enzymatic hydrolysis of biomass for the generation of cellulosic ethanol. The application of the immobilized cellobiase enzyme enabled easy post-hydrolysis separation of the enzyme from the reaction mixture. The cellobiase enzyme was immobilized in porous solid silica host material via acid catalyzed non-surfactant templated sol–gel reaction of

Sudipto Das; David Berke-Schlessel; Hai-Feng Ji; John McDonough; Yen Wei

2011-01-01

30

Fabrication of PbS nanoparticles embedded in silica gel by reverse micelles and sol-gel routes  

Microsoft Academic Search

PbS doped-silica gels showing a visible absorption onset were prepared by the sol-gel method. PbS nanoparticles with strong\\u000a quantum-confinement effect were obtained from sodium sulfide and lead nitrate by the reverse micelle method. Chemical parameters\\u000a such as the water\\/surfactant and the [Pb2+]\\/[S2?] ratios play a very important role in the PbS particle size and in their absorption threshold. The PbS

N. Pellegri; R. Trbojevich; O. De Sanctis; K. Kadono

1997-01-01

31

Nd3+-doped LiTaO3 films and powders through the sol-gel route  

Microsoft Academic Search

Nd3+-doped LiTaO3 is successfully derived by the sol-gel method. The host solution is prepared by mixing LiOC2H5 and Ta(OC2H5)5 and different concentrations of 1.0, 2.0, and 3.0 mol% of Nd3+ are introduced. The films are deposited on SiO2\\/Si substrate by spin coating and the powders are prepared by sintering the precipitation of the solution. XRD and micro-Raman studies show that

Shide D. Cheng; Chan Hin Kam; Yan Zhou; Yee-Loy Lam; Yuen Chuen Chan

1999-01-01

32

Ball milling-assisted sol–gel route to Li 4Ti 5O 12 and its electrochemical properties  

Microsoft Academic Search

Anode material Li4Ti5O12 was prepared by a ball milling-assisted sol–gel method. The as-prepared products were characterized by means of X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and electrochemical experiment. The results indicated that ball-milling and calcination temperature had significant effect on the formation of Li4Ti5O12. Phase-pure Li4Ti5O12 was obtained by sintering the ball-milled precursor at 800°C for

Guofeng Yan; Haisheng Fang; Huijuan Zhao; Guangshe Li; Yong Yang; Liping Li

2009-01-01

33

Spectroscopic study of sulforhodamine 640-doped sol–gel silica  

Microsoft Academic Search

The sol–gel process is a technique which provides a low-temperature route for the preparation of organic dye-doped porous silica glass. Extended UV transmission was observed for HCl-catalysed sol–gel silica. Properties of a solute may differ greatly between a free solution and that solution confined in pores of a sol–gel glass. Absorption and fluorescence properties of sulforhodamine 640-doped silica samples prepared

Haider Abbas; K. P. Tiwary; L. S. S. Singh; Mohd. Zulfequar; Z. H. Zaidi; M. Husain

2005-01-01

34

Synthesis of mesoporous silica-alumina materials via urea-templated sol-gel route and their catalytic performance for THF polymerization  

NASA Astrophysics Data System (ADS)

A series of mesoporous silica-alumina materials was successfully synthesized by using urea as a low-cost template via sol-gel routes. The characterization results showed that the employ of urea enhanced the porosity of the silica-alumina materials and made the pore size distributions become narrower. The specific surface area, pore volume and pore diameter of SAU-X firstly increased and then decreased as the urea concentration increased from 0 to 60 wt %, and the maximums were obtained at 40 wt % urea concentration. All samples were tested for the THF polymerization. Among them, SAU-40 exhibited the highest activity and the longest catalyst life due to its superior porosity.

Ge, Yuanyuan; Jia, Zhiqi; Gao, Chunguang; Gao, Pengfei; Zhao, Lili; Zhao, Yongxiang

2014-10-01

35

Synthesis of CdS/CdSe core/shell ultra small nanostructures using new microwave assisted ultrasonic sol gel route  

NASA Astrophysics Data System (ADS)

Core-shell CdS/CdSe nanostructures have been synthesized by new microwave assisted ultrasonic sol gel route. The solution was obtained by dissolving cadmium acetate and Thiourea in the molar ratio 1:1 in Triethlioamine. The solution was Ultrasonically irradiated by Ultrasonic crystal at 40 Hz for 3 hours at 70°C. The sol was kept for another 24 hours for gel formation. Selenium dioxide was used as a selenium source and added separately. The gel was spin coated on Quartz and Glass slides followed by microwave heat treatment. The samples were characterized by structural morphological and optical characterization. XRD studies confirm the zinc blende phase of the CdS nanoparticles. The mean nanocrystal sizes calculated using Scherrer equation is ˜1.2nm. Optical studies show the strong blue shift in the spectra due to very small size of the nanocrystals. TEM and HRTEM confirm the formation of core shell structures.

Goswami, Y. C.; Kumar, Vijay; Sharma, Ranjana; Singh, Rajeev

2014-04-01

36

Nd3+-doped LiTaO3 films and powders through the sol-gel route  

NASA Astrophysics Data System (ADS)

Nd3+-doped LiTaO3 is successfully derived by the sol-gel method. The host solution is prepared by mixing LiOC2H5 and Ta(OC2H5)5 and different concentrations of 1.0, 2.0, and 3.0 mol% of Nd3+ are introduced. The films are deposited on SiO2/Si substrate by spin coating and the powders are prepared by sintering the precipitation of the solution. XRD and micro-Raman studies show that the material displays good crystallization of pure trigonal phase of LiTaO3. AFM and SEM studies reveal that the crystalline size is about several tens of nanometers for the films and a few hundred nanometers for the powders after an annealing at 600 degree(s)C. Using the 488 nm line of an Ar+ laser as an excitation source, photoluminescence of the powders is observed at 1.06 micrometers , corresponding to the 4F3/2 yields 4I11/2 transition of Nd3+. The full width at half maximum is about 40 nm.

Cheng, Shi De; Kam, Chan Hin; Zhou, Yan; Lam, Yee Loy; Chan, Yuen Chuen

1999-10-01

37

A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties  

NASA Astrophysics Data System (ADS)

In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350 °C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65 nm was obtained at 800 °C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5 h with pseudo first order rate constants of 5.85 × 10-3 and 8.38 × 10-3 min-1, respectively.

Nassar, Mostafa Y.; Ahmed, Ibrahim S.; Samir, Ihab

2014-10-01

38

Low-Temperature Anode-Supported SOFC with Ultra-Thin Ceria-Based Electrolytes Prepared by Modified Sol—Gel Route  

NASA Astrophysics Data System (ADS)

The utilization of anode-supported electrolytes is a very promising strategy to improve the electrical performance in solid oxide fuel cells (SOFCs) application, because it is possible to decrease considerably the electrolytes thickness. In this paper, ultra-thin ceria-based electrolyte films were successfully prepared on porous NiO/GDC anode support. The electrolyte films with thickness of 0.5-1 µm were deposited by a novel citrate sol-gel route combined with a suspension spray coating technique. The characterization and microstructure of the ultra-thin films were investigated by DTA/TGA, XRD and FE-SEM. The results showed that ceria-based films prepared were pure fluorite type nanocrystalline, homogenous and almost fully dense. Electrochemical performance of single cells based on the ultra-thin electrolyte films was also tested. The single cell with electrolyte thickness of 1 µm provided an OCV of 0.832 V at 500 °C which was close to that of the reported single cell with thicker ceria-based electrolyte film of 10 µm, and maximum power densities of 59.6, 121.9 and 133.8 mW/cm2 at 500, 600, and 700 °C, respectively. These ultra-thin electrolyte films showed good combination with the porous NiO/GDC anode supports, and good insulating ability for inactive electron migration at temperatures less than 600 °C.

Lin, Hongfei; Ding, Changsheng; Sato, Kazuhisa; Tsutai, Yoshifumi; Hashida, Toshiyuki

39

Nanocrystal/sol-gel nanocomposites  

DOEpatents

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

2012-06-12

40

Nanocrystal/sol-gel nanocomposites  

DOEpatents

The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

2007-06-05

41

Sol–gel processing of hydroxyapatite  

Microsoft Academic Search

Hydroxyapatite, a calcium phosphate-based compound with numerous applications in the biological field was synthesized using the sol–gel processing route. The formation of hydroxyapatite and other compounds during the heat-treatment cycle were identified and characterized using thermal analyses and X-ray diffraction together with infrared and Raman spectroscopy. The influence of the addition of various organic alcohols (R–OH, R=CH3–, C2H5– and C3H8–)

A. Jillavenkatesa; R. A. Condrate SR

1998-01-01

42

Magnetic and 57Fe Mössbauer study of magneto-electric GaFeO3 prepared by the sol-gel route  

NASA Astrophysics Data System (ADS)

This work reports the preparation of magneto-electric GaFeO3 by the sol-gel route and its characterization by x-ray diffraction, dc-magnetization, ac-susceptibility, low temperature and high field 57Fe Mössbauer spectroscopy and dielectric constant measurements. The prepared samples are found to be single phase from x-ray diffraction studies. The crystallite sizes are found to be in the nano-regime for the samples sintered at low temperatures. From the temperature dependent dc-magnetization (M-T) measurements, bifurcation of the zero-field cooled (ZFC)-field cooled data and a cusp in the ZFC data are observed. With the help of low-field ac-susceptibility, 57Fe Mössbauer and detailed dc-magnetic measurements these features are explained in terms of the magnetic anisotropy of the sample ruling out phenomena like spin-glass and super-paramagnetism as quoted in the literature for this compound. Apart from this, very interesting and different M-H behavior mimicking composite two-phase magnets is observed for the samples sintered at different temperatures. A symmetric M-H loop is observed for samples sintered at low temperatures and a pinched M-H loop is observed for samples sintered at high temperatures. The observed magnetic properties are explained by estimating the Fe cation distribution using high field 57Fe Mössbauer spectroscopy measurements. An anomaly in the dielectric constant data at the Curie temperature indicates the ME coupling of the samples.

Sharma, Kavita; Raghavendra Reddy, V.; Gupta, Ajay; Banerjee, A.; Awasthi, A. M.

2013-02-01

43

Electrochromism of dip-coated Fe-oxide, Fe/Ti-oxide and Fe/Si-oxide films prepared by the sol-gel route  

NASA Astrophysics Data System (ADS)

Iron oxide films which were synthesized via the sol-gel route from the iron (III) chloride precursor exhibit electrochromism (Tb - Tc equals 55% at 400 nm) in LiOH (0.01 M) electrolyte. The structure of the XRD amorphous films was identified with the help of near- normal reflection absorption (6 degree(s)) (IRRA) and near-grazing incidence angle (NGIA) FT-IR spectroscopy to correspond to the nano-crystalline (gamma) -Fe2O3. Ex-situ NGIA FT-IR spectra of bleached and re-colored films were measured and it was found that the Fe-oxide films irreversibly change to the new phase in which `amorphous iron oxide' is admixed with the characteristic LO mode at 545 cm-1. Electrochemical stability of the Fe-oxide film was modified by admixing other non-absorbing Ti and Si-oxides. The structure of the mixed oxide films was identified from the corresponding IR spectra and was described as translatory disordered solid solution in which the phonon modes exhibit one mode (Fe/Ti-oxide) and two-mode (Fe/Si-oxide) behavior. Electrochemical investigations revealed that the films are able to uptake reversibly Li+, Na+, K+ ions with Q/d values in the range 0.1 - 0.31 mQ/cm2nm. The electrochromic properties of the films investigated were established from the measured in-situ UV-VIS spectroelectrochemical measurements which revealed that the electrochromic efficiencies ((Delta) OD/Q(deint)) are in the range of 6 - 14 cm2/C. The nature of the electrochromic process is discussed and correlated to the absorption edges of the various iron oxygenated compounds.

Orel, Boris; Macek, M.; Surca, A.

1994-09-01

44

Magnetic and 57Fe Mössbauer study of magneto-electric GaFeO3 prepared by the sol-gel route.  

PubMed

This work reports the preparation of magneto-electric GaFeO(3) by the sol-gel route and its characterization by x-ray diffraction, dc-magnetization, ac-susceptibility, low temperature and high field (57)Fe Mössbauer spectroscopy and dielectric constant measurements. The prepared samples are found to be single phase from x-ray diffraction studies. The crystallite sizes are found to be in the nano-regime for the samples sintered at low temperatures. From the temperature dependent dc-magnetization (M-T) measurements, bifurcation of the zero-field cooled (ZFC)-field cooled data and a cusp in the ZFC data are observed. With the help of low-field ac-susceptibility, (57)Fe Mössbauer and detailed dc-magnetic measurements these features are explained in terms of the magnetic anisotropy of the sample ruling out phenomena like spin-glass and super-paramagnetism as quoted in the literature for this compound. Apart from this, very interesting and different M-H behavior mimicking composite two-phase magnets is observed for the samples sintered at different temperatures. A symmetric M-H loop is observed for samples sintered at low temperatures and a pinched M-H loop is observed for samples sintered at high temperatures. The observed magnetic properties are explained by estimating the Fe cation distribution using high field (57)Fe Mössbauer spectroscopy measurements. An anomaly in the dielectric constant data at the Curie temperature indicates the ME coupling of the samples. PMID:23327995

Sharma, Kavita; Raghavendra Reddy, V; Gupta, Ajay; Banerjee, A; Awasthi, A M

2013-02-20

45

Estimation and Comparison of Pore Charge on Titania and Zirconia Membranes Prepared by Sol-Gel Route Using Zeta Potential Measurement  

Microsoft Academic Search

An attempt has been made to synthesize ceramic titania and zirconia membranes by sol-gel process by filtering respective viscous colloidal sol through microporous alumina support and gelling followed by sintering at 400°C and 470°C respectively. The static charge on the pores of the so formed membranes and the pore size distribution determine the applicability in filtering colloidal solution. The mean

K. S. Seshadri; M. Selvaraj; R. Kesavamoorthy; M. P. Srinivasan; K. Varatharajan; K. B. Lal; V. Krishnasamy

2003-01-01

46

Bioactive nanocrystalline sol-gel hydroxyapatite coatings.  

PubMed

Sol-gel technology offers an alternative technique for producing bioactive surfaces for improved bone attachment. Previous work indicated that monophasic hydroxyapatite coatings were difficult to produce. In the present work hydroxyapatite was synthesized using the sol-gel technique with alkoxide precursors and the solution was allowed to age up to seven days prior to coating. It was found that, similar to the wet-chemical method of hydroxyapatite powder synthesis, an aging time is required to produce a pure hydroxyapatite phase. A methodology that has been successfully used to produce nanocrystalline hydroxyapatite thin film coatings via the sol-gel route on various substrates including alumina, Vycor glass, partially stabilized zirconia, Ti-6Al-4V alloy and single crystal MgO is described. Coatings produced on MgO substrates were characterized by X-ray diffraction and atomic force microscopy, while the analogous gels were examined with thermogravimetric and differential thermal analyses. The coatings were crack free and the surface was covered with small grains, of approximately 200 nm in size for samples fired to 1000 degrees C. Coating thickness varied between 70 and 1000 nm depending on the number of applied layers. PMID:15348113

Chai, C S; Ben-Nissan, B

1999-08-01

47

A promising sol–gel route to suppress pyrochlore phase during the synthesis of multiferroic Pb(Fe 2\\/3W 1\\/3)O 3 using inorganic salts  

Microsoft Academic Search

This paper reports a promising route to synthesize multiferroic Pb(Fe2\\/3W1\\/3)O3 by sol–gel method with inorganic salts of (CH3COO)2Pb·H2O, Fe(NO3)3·9H2O, and (NH4)5H5[H2(WO4)6]·H2O. The pyrochlore phase was largely suppressed by increasing the calcination temperature, and high purity of perovskite phase was obtained at 725°C which is much lower than the temperature used in other synthesizing processes. Microstructural investigations revealed that the synthesized

C. F. Yao; Z. Q. Liu; J. K. Shang

2010-01-01

48

Structural, optical and photoelectron spectroscopic studies of nano\\/micro ZnO:Cd rods synthesized via sol-gel route  

Microsoft Academic Search

Thin films of cadmium doped zinc oxide rod like microstructure have been synthesized by a very simple sol-gel dip coating\\u000a technique. Sols were prepared from hydrated zinc oxide precursor and 2-methoxyethanol solvent with monoethanolamine as a sol\\u000a stabilizer. XRD pattern confirmed the hexagonal wurtzite structure of the deposited ZnO films. Surface morphologies of the\\u000a films have been studied by a

U. N. Maiti; P. K. Ghosh; Sk. F. Ahmed; M. K. Mitra; K. K. Chattopadhyay

2007-01-01

49

Bioactive glass-ceramic coatings prepared by pulsed laser deposition from RKKP targets (sol-gel vs melt-processing route)  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Bioactive glass-ceramic coatings for bone tissue repair and regeneration. Black-Right-Pointing-Pointer Pulsed Lased Deposition allowed congruent transfer of target composition to coating. Black-Right-Pointing-Pointer Target was prepared by sol-gel process suitable for compositional tailoring. Black-Right-Pointing-Pointer Titanium, widely used for orthopaedics and dental implants, was used as substrate. Black-Right-Pointing-Pointer The physico-chemical properties of the prepared coatings are reported. -- Abstract: The deposition of innovative glass-ceramic composition (i.e. RKKP) coatings by Pulsed Lased Deposition (PLD) technique is reported. RKKP was synthesised following two methodologies: melt-processing and sol-gel, the latter being particularly suitable to tailor the compositional range. The PLD advantage with respect to other deposition techniques is the congruent transfer of the target composition to the coating. The physico-chemical properties of films were investigated by Scanning Electron and Atomic Force Microscopies, Fourier Transform Infrared Spectroscopy, Angular and Energy Dispersive X-ray Diffraction, and Vickers microhardness. The deposition performed at 12 J/cm{sup 2} and 500 Degree-Sign C allows to prepare crystalline films with the composition that replicates rather well that of the initial targets. The 0.6 {mu}m thin melt-processing RKKP films, possessing the hardness of 25 GPa, and the 4.3 {mu}m thick sol-gel films with the hardness of 17 GPa were obtained.

Rau, J.V., E-mail: giulietta.rau@ism.cnr.it [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100-00133 Rome (Italy); Teghil, R. [Universita della Basilicata, Dipartimento di Chimica 'A.M. Tamburro', Via dell'Ateneo Lucano, 10-85100 Potenza (Italy) [Universita della Basilicata, Dipartimento di Chimica 'A.M. Tamburro', Via dell'Ateneo Lucano, 10-85100 Potenza (Italy); CNR-IMIP U.O.S. di Potenza, Zona Industriale di Tito scalo (PZ) (Italy); Fosca, M. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100-00133 Rome (Italy) [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100-00133 Rome (Italy); Universita di Roma 'La Sapienza', Dipartimento di Chimica, Piazzale Aldo Moro, 5-00185 Rome (Italy); De Bonis, A. [Universita della Basilicata, Dipartimento di Chimica 'A.M. Tamburro', Via dell'Ateneo Lucano, 10-85100 Potenza (Italy) [Universita della Basilicata, Dipartimento di Chimica 'A.M. Tamburro', Via dell'Ateneo Lucano, 10-85100 Potenza (Italy); CNR-IMIP U.O.S. di Potenza, Zona Industriale di Tito scalo (PZ) (Italy); Cacciotti, I.; Bianco, A. [Universita di Roma 'Tor Vergata', Dipartimento di Ingegneria Industriale, UR INSTM 'Roma Tor Vergata', Via del Politecnico, 1-00133 Rome (Italy)] [Universita di Roma 'Tor Vergata', Dipartimento di Ingegneria Industriale, UR INSTM 'Roma Tor Vergata', Via del Politecnico, 1-00133 Rome (Italy); Albertini, V. Rossi [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100-00133 Rome (Italy)] [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere, 100-00133 Rome (Italy); Caminiti, R. [Universita di Roma 'La Sapienza', Dipartimento di Chimica, Piazzale Aldo Moro, 5-00185 Rome (Italy)] [Universita di Roma 'La Sapienza', Dipartimento di Chimica, Piazzale Aldo Moro, 5-00185 Rome (Italy); Ravaglioli, A. [Parco Torricelli delle Arti e delle Scienze, Via Granarolo, 64-48018 Faenza (Ra) (Italy)] [Parco Torricelli delle Arti e delle Scienze, Via Granarolo, 64-48018 Faenza (Ra) (Italy)

2012-05-15

50

Sol-gel processing of a bimetallic alkoxide precursor confined in a porous glass matrix: a route to novel glass/metal oxide nanocomposites.  

PubMed

In this work we present the utilization of the heterometallic alkoxide [FeCl{Ti(2)(OPr(i))(9)}] as the first sol-gel single-source precursor to achieve nanocomposites made of iron and titanium oxides incorporated into Porous Vycor Glass (PVG). The nanocomposites were prepared by the impregnation of the precursor in a PVG plate followed by hydrolysis reactions. Different samples were obtained by further thermal treatment of the hydrolyzed sample. The nanocomposites were characterized by UV-vis-NIR, Raman and EPR spectroscopies, XRD and TEM. The results indicate that the room-temperature hydrolyzed samples are formed by nanoparticles of FeOOH and brookite-TiO(2) embedded on a glassy matrix. After the heat treatment at temperatures above 900 degrees C, a pseudobrookite Fe(2)TiO(5) was formed. All samples present high transparency and homogeneity. The results showed here indicate that the sol-gel process using the single-source precursor [FeCl{Ti(2)(OPr(i))(9)}] should be a novel and efficient approach to the preparation of nanometric Fe/Ti oxides incorporated into a glassy matrix. PMID:16494894

Menezes, Willian G; Camargo, Pedro H C; Oliveira, Marcela M; Evans, David J; Soares, Jaísa F; Zarbin, Aldo J G

2006-07-01

51

Blue green and UV emitting ZnO nanoparticles synthesized through a non-aqueous route  

NASA Astrophysics Data System (ADS)

ZnO nanoparticles of size ˜15 nm were synthesized through a non-aqueous route. TEM images showed spherical particles and elongated structures in the as prepared and annealed samples. Photoluminescence spectra showed ultraviolet luminescence arising from free exciton, donor-acceptor pairs and its LO phonon replica and deep level luminescence in blue, green and yellow regions. Annealing lead to persistent blue emission and quenching of yellow and green emissions. The ratio of the intensities of ultraviolet photoluminescence to that of visible photoluminescence increased on annealing. MicroRaman spectrum of ZnO nanoparticles showed all the non-polar and polar Raman modes. Disorder activated Raman scattering resulted in the appearance of B1 silent modes in the Raman spectra which diminished on annealing. Surface defects in the nanoparticles are responsible for the quenching of green luminescence and appearance of new modes as a result of disorder activated Raman scattering.

Rajalakshmi, M.; Sohila, S.; Ramya, S.; Divakar, R.; Ghosh, Chanchal; Kalavathi, S.

2012-06-01

52

Silica sol-gel immobilized amperometric enzyme electrode for peroxide determination in the organic phase  

Microsoft Academic Search

An amperometric enzyme electrode for peroxide determination in non-aqueous media has been constructed by the silica sol-gel immobilization of horseradish peroxidase (HRP) on a carbon paste electrode. Peroxides have been detected in the presence of ferrocene as the mediator in the organic phase to transfer electrons between the electrode surface and peroxides. The fabrication procedure of the enzyme electrode based

J Li; S. N Tan; J. T Oh

1998-01-01

53

Structural and magnetic properties of BaCoxZrxFe(12-2x)O19 prepared by citrate precursor sol-gel route  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the correlation between the distribution of cations over five crystallographic positions and magnetic properties of Ba-hexaferrites in the coupled substitution of magnetic Co2+ and non-magnetic Zr4+ for Fe3+. We have accomplished the synthesis of Co-Zr doped BaCoxZrxFe(12-2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) by citrate precursor sol-gel method under acidic conditions. Single phase M-type hexagonal ferrites are formed at 800 °C. The average size of hexagonal platelets is 34 nm. Mössbauer analysis suggests that site preferences depend upon the concentration of dopants. Dopant ions prefer 4f2 site at x = 0.4 while 12k site is largely substituted at higher dopant concentrations. Magnetic hysteresis data show that the coercive force is markedly reduced with increasing Co-Zr contents but net magnetization and coercivity are not correlated with dopant levels [MS = 61.02 emu/g, HC = 2790 Oe (x = 0); MS = 61.31 emu/g, HC = 100 Oe (x = 0.4); MS = 49.34, HC = 2134 Oe (x = 0.6); MS = 54.94 emu/g, HC = 1443 Oe (x = 1.0)]. Our results show that the magnetization and magnetocrystalline anisotropy are closely related to the distribution of Co-Zr on the five sites.

Chawla, S. K.; Mudsainiyan, R. K.; Meena, S. S.; Yusuf, S. M.

2013-06-01

54

Photorefractive sol-gel materials  

SciTech Connect

The authors report the synthesis and characterization of photorefractive sol-gel materials that possess covalently attached push-pull azobenzene and carbazole moieties. Molecular structural characterization of the modified silane monomers was achieved by {sup 1}H NMR and infra red spectroscopy. The second-order nonlinear optical properties of the organic-inorganic hybrid films prepared from modified silane monomers were evaluated by second-harmonic generation. The stabilized value of the second harmonic coefficient, d{sub 33}, of films poled by corona discharge, at 1,064 nm fundamental wavelength was found to be 107 pm/V. Photorefractivity was clearly displayed from a two beam coupling experiment.

Chaput, F.; Boilot, J.P.; Gacoin, T. [Ecole Polytechnique, Palaiseau (France); Darracq, B.; Riehl, D.; Canva, M.; Levy, Y.; Brun, A. [CNRS, Orsay (France)

1996-12-31

55

Effect of Poly(vinylpyrrolidone) As a Stress-Relaxing Additive in Fabrication of PbZrxTi1-xO3 Thin Films Using Sol-Gel Route  

NASA Astrophysics Data System (ADS)

We investigated how poly(vinylpyrrolidone) (PVP) suppresses crack generation during fabrication. It was confirmed that PVP plays the role of a stress-relaxing agent by in situ stress development measurement at temperatures from 200 to 300 °C. We found that PVP in the film was removed in two steps and that the residual PVP-decomposition product can be the cause of void generation. It was revealed that Young's modulus of the lead zirconate titanate (PZT) film prepared from PZT-PVP-sol was lower at temperatures from 300 °C to less than that from 400 °C than from PZT-sol during fabrication despite the fact that the each values at 450 °C are almost the same. It implies that PVP suppress crack formation by degrading Young's modulus of the film before crystallization. We obtained a 2-µm-thick PZT film with only 10 coatings and its electrical properties is equivalent to previously reported values obtained using the sol-gel route.

Doi, Toshihiro; Soyama, Nobuyuki; Sakurai, Hideaki

2013-09-01

56

Electrochromic properties of sol-gel derived WO3 coatings  

SciTech Connect

Amorphous tungsten oxide layers are deposited via the sol-gel route. Aqueous solutions of tungstate salts (Na2WO4) or chloroalkoxides (WOC12(OPri)2) provide cheap and suitable precursors for the synthesis of W03, nH20 colloidal solutions. Layers of large area can be deposited by spray or dip-coating. They exhibit electrochromic properties and could be used for making display devices or smart windows. Their electrochromic properties depend on the structure of the oxide network and the amount of water of the W03, nH20 layers. Switching time and stability decrease when n increases due to faster ion diffusion. Optical absorption arising from electron delocalization varies with the crystalline structure of the oxide network. Both the structure and the hydration state of the layers depend on the experimental procedure. It is therefore possible to optimize the electrochromic properties of sol-gel derived layers.

Judeinstein, P.; Livage, J.

1992-03-01

57

Non-aqueous energy storage devices using graphene nanosheets synthesized by green route  

NASA Astrophysics Data System (ADS)

In this paper we report the use of triethylene glycol reduced graphene oxide (TRGO) as an electrode material for non-aqueous energy storage devices such as supercapacitors and Li-ion batteries. TRGO based non-aqueous symmetric supercapacitor is constructed and shown to deliver maximum energy and power densities of 60.4 Wh kg-1 and 0.15 kW kg-1, respectively. More importantly, symmetric supercapacitor shows an extraordinary cycleability (5000 cycles) with over 80% of capacitance retention. In addition, Li-storage properties of TRGO are also evaluated in half-cell configuration (Li/TRGO) and shown to deliver a reversible capacity of ˜705 mAh g-1 with good cycleability at constant current density of 37 mA g-1. This result clearly suggests that green-synthesized graphene can be effectively used as a prospective electrode material for non-aqueous energy storage systems such as Li-ion batteries and supercapacitors.

Mhamane, Dattakumar; Suryawanshi, Anil; Banerjee, Abhik; Aravindan, Vanchiappan; Ogale, Satishchandra; Srinivasan, Madhavi

2013-04-01

58

Sol-gel antireflective coating on plastics  

DOEpatents

An antireflection film made from reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

Ashley, C.S.; Reed, S.T.

1988-01-26

59

Sol-gel antireflective coating on plastics  

DOEpatents

An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

Ashley, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

1990-01-01

60

Sol-gel based biofuel cell architectures  

Microsoft Academic Search

Sol-gel based biofuel cell architectures were investigated and quantified for electrochemical performance. The flexible solution chemistry of the sol-gel process has been used to synthesize bio-hybrid materials in which a wide variety of biomolecules are encapsulated in a transparent, inorganic matrix. These biomolecules retain their characteristic reactivities and spectroscopic properties despite being immobilized in the pores of the inorganic matrix.

James Robert Lim

2007-01-01

61

Sol-gel based biofuel cell architectures  

NASA Astrophysics Data System (ADS)

Sol-gel based biofuel cell architectures were investigated and quantified for electrochemical performance. The flexible solution chemistry of the sol-gel process has been used to synthesize bio-hybrid materials in which a wide variety of biomolecules are encapsulated in a transparent, inorganic matrix. These biomolecules retain their characteristic reactivities and spectroscopic properties despite being immobilized in the pores of the inorganic matrix. Stability of the biomolecules is also improved because of the confinement in the rigid inorganic network. Sol-gel immobilization serves as the basis for the electrode architecture used in enzymatic biofuel cells. In this dissertation, the fabrication and characterization of an enzymatic glucoseoxygen biofuel cell that incorporates nanostructured silica sol-gel/carbon nanotube composite electrodes was evaluated. These novel electrodes combine the benefits of sol-gel encapsulation with the use of carbon nanotubes which provide enhanced electronic conduction pathways and increase the effective surface area of the electrode. With this immobilization approach, the silica sol-gel is sufficiently porous that both glucose and oxygen have access to enzymes and yet provide a protective cage that preserves biological structure and function, offers long-term stability and perhaps enables operation at elevated temperatures. In addition, direct electron transfer was exhibited by a nanostructured cathode. More notably, these nanostructured composites were developed for power generation. Analysis of electron transfer rates and enzyme kinetics were used to quantify encapsulation properties and explore potential opportunities for optimization. Another topic for biofuel cells is miniaturization. Through miniaturization, biofuel cell design and integration are major considerations for increasing power density and performance.

Lim, James Robert

62

Sol-Gel Alumina Nano Composites for Functional Applications.  

E-print Network

??The thesis entitled "Sol-Gel Alumina Nano Composites for Functional Applications" investigate sol-gel methods of synthesis of alumina nanocomposites special reference to alumina-aluminium titanate and alumina-lanthanum… (more)

Jayasankar, M

2009-01-01

63

Sensor Performance of Nanostructured TiO2-Cr2O3 Thin Films Derived by a Particulate Sol-Gel Route with Various Cr:Ti Molar Ratios  

NASA Astrophysics Data System (ADS)

Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature and Cr:Ti molar ratio. Furthermore, it was found that Cr2O3 retarded the anatase to rutile transformation up to 800°C. The activation energy of crystallite growth was calculated to be in the range of 1.3 kJ/mol to 2.9 kJ/mol. Transmission electron microscopy (TEM) imaging showed that one of the smallest crystallite sizes was obtained for TiO2-Cr2O3 binary mixed oxide, being 5 nm at 500°C. Field-emission scanning electron microscopy (FESEM) analysis revealed that the deposited thin films had nanostructured morphology with average grain size in the range of 20 nm to 40 nm at 500°C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of NO2 gas at low operating temperature of 200°C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, calibration curves revealed that TiO2-Cr2O3 sensors followed the power law {S = A[gas]B} (where S is the sensor response, the coefficients A and B are constants, and [gas] is the gas concentration) for two types of gas, exhibiting excellent capability for detection of low gas concentrations.

Mohammadi, M. R.; Fray, D. J.

2014-07-01

64

Photophysical properties of cyanine dyes in sol-gel matrices  

Microsoft Academic Search

Planar and twisted cyanine dyes with different pKa values are examined concerning their protonation equilibrium in sol-gel matrices. In the sol-gel matrix the equilibrium between the cation and the dicationic form shifts to the dication pointing to acid-base reactions of sol-gel walls with cyanine dyes. The colorless dicationic species is not found for pseudoisocyanine and in sol-gel bulks prepared with

U. De Rossi; S. Daehne; R. Reisfeld

1996-01-01

65

MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS  

E-print Network

MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS USING AN ACOUSTIC WAVE;#12;For my Terra........ iii #12;MECHANICAL PROPERTY CHARACTERIZATION OF SOL-GEL DERIVED NANOMATERIALS, New Mexico November 2006 #12;Mechanical Property Characterization of Sol-gel Derived Nanomaterials

Brinker, C. Jeffrey

66

Sol-gel Chemistry in Medicinal Science  

Microsoft Academic Search

The sol-gel process is an inorganic polymerization process taking place in mild conditions, allowing the association of mineral phases with organic or biological systems. The possibility to immobilize drugs, enzymes, antibodies and even whole cells without loss of their biological activity led to the development of diagnostic tools, drug delivery carriers as well as new hosts for artificial organ design.

Thibaud Coradin; Michel Boissiere; Jacques Livage

2006-01-01

67

Sol-gel processing of functional and structural ceramic oxide fibers  

Microsoft Academic Search

Structural ceramic oxide fibers like ?-Al2O3, MgAl2O4 (spinel), Y3Al5O12 (YAG) and eutectic Al2O3?Y3Al5O12 as well as the functional Pb(Zr1?xTix)O3 (PZT) fibers were successfully prepared by sol-gel processing. All precursors are based on metal oxohydroxopropionates. A\\u000a comparative study of sol-gel routes leading to spinnable sols demonstrates the key role of propionic acid as an excellent\\u000a agent for controlling hydrolysis and condensation

Walther Glaubitt; Winfried Watzka; Hermann Scholz; Dieter Sporn

1997-01-01

68

Sol-gel processing of metal sulfides  

NASA Astrophysics Data System (ADS)

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 germanium mercaptide evolved during the sol-gel processing of GeSsb2. The titrations were performed in 2-propanol or in a 50-50 vol % mixture of 2-propanol and toluene. The ion selective Ag/Agsb2S electrode was used for equivalence point detection. Study of the Nernst equation shows that complexes were formed at the electrode surface. However, the titration equivalence point volume clearly demonstrates the formation of Agsb2S and Ge(SAg)sbn. In order to explain this discrepancy a new electrode reaction mechanism and a modified Ag/Agsb2S electrode potential equation are proposed. Effects of hydrogen sulfide and germanium ethoxide concentrations, the concentration ratio and temperature on the microstructure of the prepared GeSsb2 gels were studied. It was found that the concentrations of the reactants have the most significant influence on gel structure.

Stanic, Vesha

69

Strip-loaded sol-gel waveguides for optical amplifiers  

NASA Astrophysics Data System (ADS)

Among the various possible production techniques of silica- on-silicon integrated optical devices, sol-gel is the one which combines low cost with a great flexibility and the ease of doping the silica matrix with nonlinear and active compounds. In the frame of an European project, we have investigated the application of the sol-gel technique to the realization of an erbium-doped optical amplifier, operating in the third telecommunication window. Here, in particular, we refer to the development of an optimum fabrication strategy for the guiding structure. A strip-loaded configuration was chosen. Design optimization was carried out by means of a MATLAB software code, mainly based on the Effective Index Method. For what concerns the technical side, two different routes were followed: that of the Low Index Load and that of the High Index Load. Pros and cons of both structures were carefully evaluated through numerical simulations as well as experimental analysis, in order to choose the best performing one. Results of the design procedure and the characterization of the fabricated waveguides are described here.

Forastiere, Michele A.; Guglielmi, Massimo; Martucci, Alessandro; Ahmad, Munir M.; McCarthy, O.; Pelli, Stefano; Righini, Giancarlo C.; Vannucci, A.; Yeatman, Eric M.

1999-04-01

70

Strip-Loaded Sol-Gel Waveguides  

NASA Astrophysics Data System (ADS)

Sol-gel is one of the most attractive techniques for production of silica-on-silicon integrated optical devices. In fact, it combines low cost with flexibility and ease of doping; thus, nonlinear and active compounds can be effectively included in the silica matrix. Here, the feasibility of applying the sol-gel technique to the realization of an erbium-doped optical amplifier is reported on, operating in the third telecommunication window. In particular, the development of an optimum strategy for the design and fabrication of a guiding structure in the strip-loaded configuration is described. Design optimization results, as well as fabrication results and measured characteristics, are described and discussed.

Forastiere, Michele A.; Pelli, Stefano; Righini, Giancarlo C.; Guglielmi, Massimo; Martucci, Alessandro; Ahmad, Munir M.; McCarthy, Orla; Yeatman, Eric; Vannucci, Antonello

71

Sol-Gel PZT for MEMS Applications  

Microsoft Academic Search

Thin-film piezoelectric materials offer an alternative transduction mechanism to electrostatic actuation and capacitive sensing with many attractive advantages for applications in microelectromechanical systems (MEMS). Researchers at the U.S. Army Research Laboratory are utilizing sol-gel deposited lead zirconate titanate (PZT) thin-films in developing several new MEMS technologies, including high frequency filters, magnetometers, micropumps, and pressure sensors. The fabrication procedure and an

Brett Piekarski; Madan Dubey; Eugene Zakar; Ronald Polcawich; Don Devoe; Dennis Wickenden

2002-01-01

72

Sol-Gel Manufactured Energetic Materials  

DOEpatents

Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

Simpson, Randall L. (Livermore, CA); Lee, Ronald S. (Livermore, CA); Tillotson, Thomas M. (Tracy, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Swansiger, Rosalind W. (Livermore, CA); Fox, Glenn A. (Livermore, CA)

2005-05-17

73

Sol-gel based optical chemical sensors  

NASA Astrophysics Data System (ADS)

The growing activity in the field of optical chemical sensors has resulted in numerous sensing schemes, new indicator dyes, various polymeric matrix, size and shapes and highly diversified methods of immobilization. The sensor characteristics are dependent upon the choice of indicator, polymer, immobilization technique, and also size. Sol-gel technology provides a low-temperature method for obtaining porous silicate glass matrices. It enables to obtain material in the form of films, powders, monoliths, fibres or nanoparticles. Organic reagents and molecular receptors can be easily immobilized in the matrices. Moreover, one of the unique features of the sol-gel process is that the properties of the final network structure, such as hydrophobicity, thickness, porosity, flexibility, reactivity and stability can be easily tailored by controlling the process conditions, the type and the size of the precursors and catalysis. Here we will report about several sensor designed over the years based on sol-gel materials for monitoring and controlling different parameters, such as heavy metals, amines, phosphates, organophosphates.

Lobnik, Aleksandra; Korent Urek, Špela; Turel, Matejka; Fran?i?, Nina

2011-05-01

74

Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby  

NASA Technical Reports Server (NTRS)

A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

2002-01-01

75

Substituent effects on the sol-gel chemistry of organotrialkoxysilanes  

SciTech Connect

Silsesquioxanes have been the subject of intensive study in the past and are becoming important again as a vehicle for introducing organic functionalities into hybrid organic-inorganic materials through sol-gel processing. Depending on the application, the target hybrid material may be required to be a highly cross-linked, insoluble gel or a soluble polymer that can be cast as a thin film or coating. The former has applications such as catalyst supports and separations media; the latter is an economically important method for surface modification or compatiblization for applying adhesives or introducing fillers. Polysilsesquioxanes are readily prepared through the hydrolysis and condensation of organotrialkoxysilanes, though organotriaminosilane and organotrihalosilane monomers can also be used. This paper explores the kinetics of the preparation route.

LOY, DOUGLAS A.; BAUGHER, BRIGITTA M.; BAUGHER, COLLEEN R.; SCHNEIDER, DUANE A.; RAHIMIAN, KAMYAR

2000-05-09

76

Synthesis and characterization of La 0.8 Sr 0.2 Co 0.5 Fe 0.5 O 3±? nanopowders by microwave assisted sol–gel route  

Microsoft Academic Search

Nano-crystalline La0.8Sr0.2Co0.5Fe0.5O3?? powder has been successfully synthesized by microwave assisted sol–gel (MWSG) method. The decomposition and crystallization\\u000a behavior of the gel-precursor was studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis.\\u000a From the result of FT-IR and X-ray diffraction patterns, it is found that a perovskite La0.8Sr0.2Co0.5Fe0.5O3?? was formed by irradiating the precursor at 700 W for 3 min,

Shiming Liu; Xiaoliang Qian; Jianzhong Xiao

2007-01-01

77

Sol-gel method for encapsulating molecules  

DOEpatents

A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Bhatia, Rimple (Albuquerque, NM); Singh, Anup K. (San Francisco, CA)

2002-01-01

78

Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase  

ERIC Educational Resources Information Center

This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor…

Kulkarni, Suhasini; Tran, Vu; Ho, Maggie K.-M.; Phan, Chieu; Chin, Elizabeth; Wemmer, Zeke; Sommerhalter, Monika

2010-01-01

79

Sol–gel coatings on metals for corrosion protection  

Microsoft Academic Search

Sol–gel protective coatings have shown excellent chemical stability, oxidation control and enhanced corrosion resistance for metal substrates. Further, the sol–gel method is an environmentally friendly technique of surface protection and had showed the potential for the replacement of toxic pretreatments and coatings which have traditionally been used for increasing corrosion resistance of metals. This review covers the recent developments and

Duhua Wang; Gordon. P. Bierwagen

2009-01-01

80

Investigations of the small-scale thermal behavior of sol-gel thermites.  

SciTech Connect

Sol-gel thermites, formulated from nanoporous oxides and dispersed fuel particles, may provide materials useful for small-scale, intense thermal sources, but understanding the factors affecting performance is critical prior to use. Work was conducted on understanding the synthesis conditions, thermal treatments, and additives that lead to different performance characteristics in iron oxide sol-gel thermites. Additionally, the safety properties of sol-gel thermites were investigated, especially those related to air sensitivity. Sol-gel thermites were synthesized using a variety of different techniques and there appear to be many viable routes to relatively equivalent thermites. These thermites were subjected to several different thermal treatments under argon in a differential scanning calorimeter, and it was shown that a 65 C hold for up to 200 minutes was effective for the removal of residual solvent, thus preventing boiling during the final thermal activation step. Vacuum-drying prior to this heating was shown to be even more effective at removing residual solvent. The addition of aluminum and molybdenum trioxide (MoO{sub 3}) reduced the total heat release per unit mass upon exposure to air, probably due to a decrease in the amount of reduced iron oxide species in the thermite. For the thermal activation step of heat treatment, three different temperatures were investigated. Thermal activation at 200 C resulted in increased ignition sensitivity over thermal activation at 232 C, and thermal activation at 300 C resulted in non-ignitable material. Non-sol-gel iron oxide did not exhibit any of the air-sensitivity observed in sol-gel iron oxide. In the DSC experiments, no bulk ignition of sol-gel thermites was observed upon exposure to air after thermal activation in argon; however ignition did occur when the material was heated in air after thermal treatment. In larger-scale experiments, up to a few hundred milligrams, no ignition was observed upon exposure to air after thermal activation in vacuum; however ignition by resistively-heated tungsten wire was possible. Thin films of thermite were fabricated using a dispersed mixture of aluminum and iron oxide particles, but ignition and propagation of these films was difficult. The only ignition and propagation observed was in a preheated sample.

Warren, Mial E.; Farrow, Matthew; Tappan, Alexander Smith

2009-02-01

81

Solid-state NMR study of geopolymer prepared by sol-gel chemistry  

SciTech Connect

Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer. -- Graphical abstract: Geopolymer prepared by the sol-gel route has the same spectroscopic properties as the sample prepared from the natural kaolinite. Display Omitted

Tsai, Yi-Ling [Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan ROC (China); Hanna, John V. [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Lee, Yuan-Ling, E-mail: yuanlinglee@ntu.edu.t [Graduate Institute of Clinical Dentistry, National Taiwan University and Hospital, No. 1, Changde Street, Taipei 10048, Taiwan ROC (China); Smith, Mark E., E-mail: M.E.Smith.1@warwick.ac.u [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Chan, Jerry C.C., E-mail: chanjcc@ntu.edu.t [Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan ROC (China)

2010-12-15

82

Photophysical properties of cyanine dyes in sol-gel matrices  

NASA Astrophysics Data System (ADS)

Planar and twisted cyanine dyes with different p Ka values are examined concerning their protonation equilibrium in sol-gel matrices. In the sol-gel matrix the equilibrium between the cation and the dicationic form shifts to the dication pointing to acid-base reactions of sol-gel walls with cyanine dyes. The colorless dicationic species is not found for pseudoisocyanine and in sol-gel bulks prepared with drying control chemical agents (DCCA) indicating the absence of the responsible interaction. The fluorescence lifetimes of cyanine molecules are used to compare the pore size and distribution in sol-gel matrices prepared with and without DCCA. J-aggregation, examined for one dye, depends strongly on environment polarity and pore size.

De Rossi, U.; Daehne, S.; Reisfeld, R.

1996-03-01

83

Bimetallic colloids of silver and copper in thin films: sol–gel synthesis and characterization  

Microsoft Academic Search

A sol–gel route to synthesize thin films containing alloy- and phase separated mixed-colloids of silver (Ag) and copper (Cu) has been developed. Ag–Cu alloy colloids with Ag:Cu molar ratios of 4:1–1:2 in the coatings were obtained by the addition of copper ions stabilized in a pre-hydrolyzed SiO2-sol in the presence of hydroxylamine hydrochloride, to a colloidal silver sol stabilized by

Ganesh Suyal

2003-01-01

84

Ionic conductivity of Bi2NixV1-xO5.5-3x/2 (0.1 ? x ? 0.2) oxides prepared by a low temperature sol-gel route  

NASA Astrophysics Data System (ADS)

Solid oxides fuel cells (SOFCs) is one technology that could contribute toward future sustainable energy. One of the most important components of an SOFC is the electrolyte, which must have high ionic conductivity. Cation substitution of vanadium in Bi4V2O11 yields a family of fast oxide ion conducting solids known collectively as the BIMEVOXes (bismuth metal vanadium oxide), which have the potential to be applied as electrolytes in SOFCs. The purpose of this work is to study the effect of Ni concentration, when used as a dopant, on the ionic conductivity of Bi2NixV1-xO5.5-3x/2 (BINIVOX) oxides (0.1 ? x ? 0.2) when prepared by a sol gel method. The gels were calcined at 600 °C for 24 h to produce pure BINIVOX. These oxides were found to exhibit the ?-phase structure with tetragonal symmetry in space group I4/mmm. Ionic conductivity of BINIVOX at 300 °C were 6.9 × 10-3 S cm-1, 1.2 × 10-3 S cm-1, and 8.2 × 10-4 S cm-1, for x = 0.1; 0.15; and 0.2; respectively; and at 600 °C were 1.1 × 10-1 S cm-1, 5.3 × 10-2 S cm-1, and 2.8 ×10-2 S cm-1, for x = 0.1; 0.15; and 0.2; respectively.

Rusli, Rolan; Abrahams, Isaac; Patah, Aep; Prijamboedi, Bambang; Ismunandar

2014-03-01

85

Sol-Gel Fabrication of Glass Fibers for Optics  

Microsoft Academic Search

\\u000a The chemistry and physics of the sol-gel fabrication of Si02 glass fibers, by direct spinning of silicon alkoxide-derived viscous sols and by melt-drawing of sol-gel-derived preforms,\\u000a are reviewed„ The sol-gel method has been extended to the fabrication of high refractive index PbO-TiO2 glass fibers. Third order optical nonlinear susceptibilities X(3) as high as ~10-12 esu are obtained in these glasses.

Kanichi Karniya

86

Effect of seeding on the formation of lanthanum hexaaluminates synthesized through advanced sol gel process  

NASA Astrophysics Data System (ADS)

Advanced sol gel processing was used to synthesize high purity lanthanum hexaaluminate powders. The effect of seeding on the formation of lanthanum hexaaluminate was also studied by seeding the gel. Dry gel was calcined at various temperatures starting from 1100 °C to 1600 °C for 2 h to study the phase evolution. The combine effects of advanced sol gel processing and the presence of seeds promoted the formation of lanthanum hexaaluminate phase at lower temperature than the conventional routes. Lanthanum hexaaluminate phase was detected at 1201 °C and 1300 °C in seeded and un-seeded gels, respectively. The presence of seed decreases the temperature of formation of lanthanum hexaaluminate by 99 °C. Single phase lanthanum hexaaluminate was formed at 1600 °C in seeded gel whereas trace of lanthanum monoaluminate phase still present in un-seeded gel even at 1600 °C.

Jana, P.; Jayan, P. S.; Mandal, S.; Biswas, K.

2014-12-01

87

Soluble polymers in sol-gel silica  

NASA Astrophysics Data System (ADS)

In the last few years, the inherent versatility of sol-gel processing has led to a significant research effort on inorganic/organic materials. One method of incorporating an organic phase into sol-gel silica is dissolving an organic polymer in a tetraethylorthosilicate (TEOS) solution, followed by in situ polymerization of silica in the presence of organic polymer. The first part of the study involved the development of a two-step (acid-base) synthesis procedure to allow systematic control of acidity in TEOS solutions. With this procedure, it was possible to increase the pH of the TEOS solution while correlating the acidity and properties. The properties were the gelation time, syneresis rate, drying behavior, and xerogel pore structure, as determined by nitrogen sorption. Furthermore, controlling the acidity was shown to control the silica xerogel pore structure. In the second part of the study, the two-step procedure was used to synthesize silica/poly(ethylene glycol) (PEG), and silica/poly(vinyl acetate) (PVAc) composite materials. The content of organic polymer and the molecular weight were varied. The gelation time, the syneresis rate, the drying behavior, and the pore structure were determined for compositions with 10% PEG (M.W. 2,000), 5, 10, and 15% PEG (M.W. 3,400), and 10 and 25% PVAc (M.W. 83,000). Other compositions and molecular weights of PEG lead to sedimentation. In the PEG compositions, the tendency to phase separate was correlated with the effects of the processing variables on the segregation strength and polymerization rate. The PVAc compositions did not show any visible phase separation during processing, giving the composite xerogels an appearance similar to pure silica. The property differences between gels with PEG and gels with PVAc show the relative strength of the interactions with silica. Both polymers exhibit hydrogen bonding between the phases. In the case of PEG, hydrogen bonding between the ether oxygens of the polymer and silanol groups of the hydrolyzed TEOS reduce the gelation time. In the case of PVAc, hydrogen bonding between carbonyl groups of the polymer and silanol groups delay gelation and may physically interfere with condensation. As the competition between the rates of condensation and phase separation are a function of processing conditions, we obtained xerogels that ranged from transparent to opaque.

Beaudry, Christopher Laurent

88

Sol-gel fluxes for flux cored welding consumables  

SciTech Connect

The feasibility of producing high purity homogeneous welding fluxes by the sol-gel process and the effects that these fluxes have on the welding process were determined. Reagent grade sol-gel welding fluxes were produced by making systematic variations of the SiO/sub 2/-CaO-TiO/sub 2/-1 pct Na/sub 2/O flux system. The resulting fluxes were made into flux cored wires and used to make bead on plate welds on a niobium microalloyed HSLA steel. Sol-gel fluxes were shown to have excellent homogeneity, low residual hydrogen content, and no apparent water adsorption. The welding behaviour of the sol-gel fluxes was shown to have superior arc stability compared to a commercial flux cored wire and very low weld metal hydrogen content.

Dunn, P.S.; Natalie, C.A.; Olson, D.L.

1986-09-01

89

Sol-gel glasses as new waveguides for optical immunosensors  

SciTech Connect

In order to develop an optical immunosensor based on Surface Plasmon Resonance (SPR) and guided waves propagation, the sol-gel process has been used to prepare thin films of amorphous silica, deposited by spin coating on a gold-coated glass slide, and possessing chemically active functional groups (SH, NH{sub 2} ... ). After activation of the Sol-gel film in aqueous buffers by a bifunctional coupling agent, biological molecules such as antibodies could be covalently bonded on or inside the sol-gel film. Therefore, the behavior of the functionalized silica thin films in aqueous solutions has been analyzed by SPR and guided waves propagation. The matrix hydrophilicity has been studied with different mixtures of functionalized silicon precursors forming organic-inorganic hybrid films. Immunoassays outline the possibility of obtaining covalent binding of antibodies to the sol-gel matrix with optimal stability and biological activity.

Collino, R.; Therasse, J. [Centre d`Etudes du Bouchet, Vert-le-Petit (France); Chaput, F.; Boilot, J.P. [Ecole Polytechnique, Palaiseau (France); Levy, Y. [Inst. d`Optique Theorique et Appliquee, Orsay (France)

1994-12-31

90

Nanostructured Energetic Materials with Sol-Gel Methods  

Microsoft Academic Search

The utilization of sol-gel chemical methodology to prepare nanostructured energetic materials as well as the concepts of nanoenergetics is described. The preparation and characterization of two totally different compositions is detailed. In one example, nanostructured aerogel and xerogel composites of sol-gel iron (III) oxide and ultra fine grained aluminum (UFG Al) are prepared, characterized, and compared to a conventional micron-sized

A Gash; J Satcher; R Simpson; B Clapsaddle

2003-01-01

91

Thick film sol gel PZT transducer using dip coating  

Microsoft Academic Search

A sol gel process has been used to develop a 30 ?m thick PZT coating on a sapphire wafer. The sol gel film was removed and plated with platinum electrodes. The free-standing film had a free dielectric constant (?T) of 820, a thickness-mode coupling coefficient (kt) of 0.17, a speed of sound (c) of 3700 m\\/s, and an acoustic impedance

Kenneth L. Gentry; Jason M. Zara; Sang-Don Bu; Chang-Beom Eom; Stephen W. Smith

2000-01-01

92

Raman Studies of the Nanostructure of Sol-Gel Materials  

Microsoft Academic Search

Four sol-gel systems (alumina, aluminum hydroxide, zirconia, and magnesia) were investigated, primarily by laser spectroscopy, on several series of materials prepared by systematically varying the synthesis procedures. Nanocrystalline boehmite, gamma -AlO(OH), was found to be the principal component in the sol-gel alumina system. Materials were prepared by the hot-water hydrolysis\\/condensation of rm Al(OC_4H_9)_3, the Yoldas process, as a function of

Calvin James Doss

1994-01-01

93

Replicated optical MEMS in sol-gel materials  

Microsoft Academic Search

Replication technology using sol-gel materials offers an interesting alternative to the current approach to optical MEMS fabricated in silicon using lithographic and micro-machining technologies. The use of UV-curable sol-gel materials enables optical features such as micro-lenses and diffractive optical elements to be fabricated in the same process step as the MEMS structures, and has the potential of low-cost, high resolution

M. T. Gale; S. Obi; N. de Rooij

2003-01-01

94

Replicated optical MEMS in sol-gel materials  

Microsoft Academic Search

Replication technology using sol-gel materials offers an interesting alternative to the current approach to optical microelectromechanical systems (MEMS) fabricated in silicon using lithographic and micromachining technologies. The use of UV-curable sol-gel materials enables optical features such as microlenses and diffractive optical elements to be fabricated in the same process step as the MEMS structures, and has the potential of low-cost

S. Obi; M. T. Gale; C. Gimkiewicz; S. Westenhofer

2004-01-01

95

Sol–gel preparation and characterization of gadolinium aluminate  

Microsoft Academic Search

This paper reports on the results concerning the sol–gel preparation of nanocrystalline gadolinium aluminate (GdAlO3, GAP) using different starting materials. The gadolinium nitrate or gadolinium oxide as Gd raw compounds and aluminium nitrate as Al source were used in the sol–gel processing. The metal ions, generated by dissolving starting materials of metals in the diluted acetic acid were complexed by

S. Cizauskaite; V. Reichlova; G. Nenartaviciene; A. Beganskiene; J. Pinkas; A. Kareiva

2007-01-01

96

Dip coating of sol-gels  

SciTech Connect

Dip coating is the primary means of depositing sol-gel films for precision optical coatings. Sols are typically multicomponent systems consisting of an inorganic phase dispersed in a solvent mixture, with each component differing in volatility and surface tension. This, together with slow coating speeds (<1cm/s), makes analysis of the coating process complicated; unlike most high-speed coating methods, solvent evaporation, evolving rheology, and surface tension gradients alter significantly the fluid mechanics of the deposition stage. We set out to understand these phenomena with computer-aided predictions of the flow and species transport fields. The underlying theory involves mass, momentum, and species transport on a domain of unknown shape, with models and constitutive equations for vapor-liquid equilibria and surface tension. Due accounting is made for the unknown position of the free surface, which locates according to the capillary hydrodynamic forces and solvent loss by evaporation. Predictions of the effects of mass transfer, hydrodynamics, and surface tension gradients on final film thickness are compared with ellipsometry measurements of film thickness on a laboratory pilot coater. Although quantitative agreement is still lacking, both experiment and theory reveal that the film profile near the drying line takes on a parabolic shape. 2 refs., 2 figs.

Schunk, P.R.; Hurd, A.J.; Brinker, C.J.

1991-01-01

97

Electrophoretic Porosimetry of Sol-Gels  

NASA Technical Reports Server (NTRS)

It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.

Snow, L. A.; Smith, D. D.; Sibille, L.; Hunt, A. J.; Ng, J.; Rose, M. Franklin (Technical Monitor)

2000-01-01

98

Sol-gel-derived percolative copper film  

SciTech Connect

Cu-SiO{sub 2} films were prepared by the sol-gel method. Two-dimensional fractal copper films were formed after the films were thermally treated in reducing atmosphere. dc resistances of the films decrease 12 orders of magnitude as the content of copper increases from 70 to 80 mol%. During the resistance measurement under argon atmosphere, samples showed a sharp increase or decrease of resistance at a transition temperature which is ascribed to the oxidation of Cu into CuO. The oxidation was also observed in the in situ high temperature X-ray diffraction under vacuum condition. The evolution of the morphology of the films was studied by scanning electron microscopy. As the content of copper increases, the forms of copper particles change from discrete to aggregate then to interconnecting. The coverage coefficients of the copper range from 23 to 55% and the fractal dimensions range from 1.65 to 1.77. The percolation thresholds for the coverage coefficient and the fractal dimension are about 33% and 1.71, respectively, which corresponds to the sample containing 72.5 mol% of Cu.

Szu Sungping [Department of Physics, National Chung-Hsing University, Taichung 402, Taiwan (China)], E-mail: spszu@phys.nchu.edu.tw; Cheng, C.-L. [Department of Physics, National Chung-Hsing University, Taichung 402, Taiwan (China)

2008-10-02

99

Hydrophilic and optical properties of nanostructured titania prepared by sol-gel dip coating  

NASA Astrophysics Data System (ADS)

Nanostructured titania thin films were prepared under controlled atmospheric conditions by the sol-gel dip-coating technique on glass, fused silica and (1 0 0)-silicon substrates. Two different sol-gel routes were employed by using different precursor solutions, a highly acid solution and a polymer-like solution. The influence of sol composition and of the substrate type on the morphology, coating porosity, surface roughness, crystalline phases and grain size of the titania films were investigated in detail. In addition, the relationship between microstructural/morphological properties and the optical properties (energy gap, refractive index and extinction coefficient) and the hydrophilic performance of the coatings were evaluated. Our experimental results clearly indicate that the sol composition and substrate type remarkably influence the films' morphology and microstructure; moreover, they consequently modify the optical response and hydrophilic performances of the samples, showing that superhydrophilic titania coatings can be obtained opportunely by choosing the composition of the precursor sol-gel solution. Blue shift of the band gap energy and a band structure mutation from indirect to direct were also revealed. The hydrophilic properties and the change in the band gaps transition can be attributed to oxygen vacancies on the surface of the titania nanocrystallites that gives rise to Ti3+ sites and, consequently, to structural changes/defects of the anatase nanoarchitecture. These findings allow us to design and tailor the optical and hydrophilic properties of the titania coatings.

Ferrara, M. C.; Pilloni, L.; Mazzarelli, S.; Tapfer, L.

2010-03-01

100

Synthesis and characterization of transparent mesoporous materials by a non-aqueous sol gel method  

NASA Astrophysics Data System (ADS)

New inorganic-organic hybrid mesoporous materials were prepared by chemical modification of polymethylhydrosiloxane by 1,2-diaminopropane and 1,2-diaminocyclohexane, in tetrahydrofuran, using hexachloroplatinic acid (H 2PtCl 6 · 6H 2O) as catalyst at room temperature. This reaction leads to the formation of transparent and monolithic gels. The products have been characterized by infrared and 29Si CP MAS NMR spectroscopy. The results show that the organic components have reacted with the polymethylhydrosiloxane leading to colourless and coloured gels in which both organic-inorganic bridges are formed. The thermal treatment procedure was determined by TGA and DTA curves recorded on the hybrid gel powder drying at 100 °C during 24 h. Xerogels morphology and texture were performed by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller method (BET).

Sediri, F.; Chine, M. K.; Gharbi, N.

2008-06-01

101

Dielectric Bilayer Films Comprising Polar Cyanolated Silica Sol-Gel and Nanoscale Blocking Layer for Energy Storage Applications  

NASA Astrophysics Data System (ADS)

Organic-inorganic hybrid sol-gel containing polar groups, which can undergo orientational polarization under the influence of an electric field, provide a potential route to processable and rational design of materials for energy storage applications. However, the porous nature of sol-gel films, which significantly lowers breakdown strength, limits the potential of this material for energy storage particularly in high-field applications. In this work, we fabricate and characterize dielectric bilayer films comprising cyanolated silica sol-gel film prepared from 2-cyanoethyltrimethoxysilane (CNETMS) precursor and nanoscale blocking layers, which include amorphous fluoropolymer, SiO2, Al2O3 and ZrO2 deposited by spin casting, electron beam evaporation or atomic layer deposition (ALD). CNETMS films with 50 nm ZrO2 blocking layer exhibit an extractable energy density of 13 J/cm^3, which is about a twofold enhancement compared to CNETMS films without blocking layer. The effect of the blocking layer will be discussed in terms of surface morphology, dielectric contrast, i.e. the ratio of relative permittivity between oxide layer and sol-gel film, electric field distribution, breakdown strength and statistics, bias polarity, and loss of the bilayer films.

Kathaperumal, Mohanalingam; Kim, Yunsang; Smith, O'neil; Dindar, Amir; Fuentes-Hernandez, Canek; Hwang, Do-Kyung; Pan, Ming-Jen; Kippelen, Bernard; Perry, Joseph

2013-03-01

102

Calcium biosensing with a sol-gel immobilized photoprotein.  

PubMed

Aequorin, the bioluminescent protein found in the jellyfish Aequorea sp., has been immobilized in a porous sol-gel glass environment. The luminescence from this protein is specifically triggered by the presence of calcium ions, thus offering exciting possibilities for the development of an optical biosensor for this cationic species. The luminescence emission spectrum has been measured from the aequorin protein after interaction with calcium ions. The intensity of the luminescence, measured at the peak maximum of 470 nm, for the encapsulated protein has been calibrated against calcium ion concentration. The characterization of the protein within the sol-gel matrix has been reported together with biosensing experiments using human sera and milk samples. The results suggest that the sol-gel encapsulated aequorin protein offers potential as a one shot bioluminescence based biosensor for the determination of calcium ions in such complex matrices. PMID:9008410

Blyth, D J; Poynter, S J; Russell, D A

1996-12-01

103

Synthesis and characterisation of tantalum-incorporating silica hybrid sol gel thin films for optical applications  

NASA Astrophysics Data System (ADS)

A new acrylate-modified silica incorporating tantalum is synthesised via a sol-gel route. After deposition, the few micron-thick films can be photo-polymerised by UV-irradiation. FTIR spectroscopy gives a first insight into the curing process and the chemical structure of the hybrid material. The refractive index of the layers can be modulated by varying the concentration of tantalum in the material. Coatings exhibit a good transparency in the blue range of the optical spectrum. Finally, the propagation losses are low enough to make the material suitable for applications in integrated optics.

Blanc, Danièle; Zhang, Weiping; Massard, Christophe; Mugnier, Jacques

2006-03-01

104

Cd 2 SnO 4 -its sol-gel preparation and materials properties  

Microsoft Academic Search

Cd2SnO4 powder has been synthesized through acrylamide sol-gel route for the first time. The gelation-calcination steps have been\\u000a studied. Morphological examination of the network matrix and the calcined products has been done through SEM. XRD shows the\\u000a orthorhombic structure of the Cd2SnO4 powder obtained. Arrhenius plots yield activation energies of 0·01 and 0·61 eV for the low and high slope

M Jayachandran; B Subramanian; Mary Juliana; Chockalingam; A S Lakshmanan

1994-01-01

105

Solid-state NMR study of geopolymer prepared by sol-gel chemistry  

NASA Astrophysics Data System (ADS)

Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer.

Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling; Smith, Mark E.; Chan, Jerry C. C.

2010-12-01

106

Low-temperature preparation of nanoplated bismuth titanate microspheres by a sol–gel-hydrothermal method  

Microsoft Academic Search

A layered inorganic perovskite micrometer-scale material, nanoplated bismuth titanate (Bi4Ti3O12) microspheres (NBTMs) constructed with tens of Bi4Ti3O12 nanoplates, was for the first time synthesized by a novel sol–gel-hydrothermal route. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy. The results indicated that the NBTMs possessed an average diameter of about 1.0?m

Zhiwu Chen; Xinhua He

2010-01-01

107

Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials  

NASA Technical Reports Server (NTRS)

An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

Fang, Jonathan; Zhou, Jing C.; Lan, Esther H.; Dunn, Bruce; Gillman, Patricia L.; Smith, Scott M.

2004-01-01

108

Sol-gel stationary phases for capillary electrochromatography.  

PubMed

A review is presented on the current state of the art and future trends in the development of sol-gel stationary phases for capillary electrochromatography (CEC). The design and synthesis of stationary phases with prescribed chromatographic and surface charge properties represent challenging tasks in contemporary CEC research. Further developments in CEC as a high-efficiency liquid-phase separation technique will greatly depend on new breakthroughs in the area of stationary phase development. The requirements imposed on CEC stationary phase performance are significantly more demanding compared with those for HPLC. The design of CEC stationary phase must take into consideration the structural characteristics that will provide not only the selective solute/stationary phase interactions leading to chromatographic separations but also the surface charge properties that determine the magnitude and direction of the electroosmotic flow responsible for the mobile phase movement through the CEC column. Therefore, the stationary phase technology in CEC presents a more complex problem than in conventional chromatographic techniques. Different approaches to stationary phase development have been reported in contemporary CEC literature. The sol-gel approach represents a promising direction in this important research. It is applicable to the preparation of CEC stationary phases in different formats: surface coatings, micro/submicro particles, and monolithic beds. Besides, in the sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. One remarkable advantage of the sol-gel approach is the mild thermal conditions under which the stationary phase synthesis can be carried out (typically at room temperature). It also provides an effective pathway to integrating the advantageous properties of organic and inorganic material systems, and thereby enhancing and fine-tuning chromatographic selectivity of the created hybrid organic-inorganic stationary phases. This review focuses on recent developments in the design, synthesis, characterization, properties, and applications of sol-gel stationary phases in CEC. PMID:15354427

Li, Wen; Fries, David P; Malik, Abdul

2004-07-30

109

Silica scintillating materials prepared by sol-gel methods  

SciTech Connect

Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons.

Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

1993-12-31

110

Highly photoconductive PVK/TNF sol-gel materials  

NASA Astrophysics Data System (ADS)

A photoconductive sol-gel material based on the incorporation of polyvinyl carbazole (PVK) and 2,4,7-trinitro-9-fluorenone (TNF) within a silica matrix is reported. Unmatched photosensitive as large as 10-10 cm/?W has been found at moderate applied electric fields (20 V/?m). The optimization of the concentration balance between the functional component (the TNF/PVK molar ratio percent) has resulted in a 300-fold increase of the photocurrent efficiency (?). The study of photcoductivity of sol-gel materials prepared with different PVK contents has confirmed the unneeded use of massive photoconductive materials to obtain optimum performance.

del Monte, Francisco; Ramos, Gonzalo; Belenguer, Tomas; Levy, David

2003-12-01

111

Sol-gel and mod processing of layered perocskite films  

Microsoft Academic Search

Sol-gel and MOD processes have been used to deposit layered perovskite films such as Bi4Ti3O12, SrBi2Ta2O9 and SrBi2NbTaO9 films on top of Si(100) substrates with Ti\\/Pt electrodes. Their structural and electrical properties have been studied as a function of processing. Additionally sol-gel and MOD processes have been applied for SrTiO3 films. The morphology of the layers has been characterised and

Mareike Klee; Uwe Mackens

1996-01-01

112

Sensitive films based on porous sol-gel silica  

NASA Astrophysics Data System (ADS)

The paper is devoted to the sensitive films for application in chemical sensors. These films, made of the sol-gel derived porous silica, were fabricated via a sol-gel dip-coating method. We have obtained silica layers of the minimum refractive index of ~ 1.22 and porosity ~47%. These layers were sensitized with a pH indocator - bromocresole purple. The indicator was introduced into porous silica layers by means of impregnation. Methods and results of characterization of porous silica films, before and after sensitization are presented in this paper. It was shown that films are very sensitive toward ammonia.

Karasi?ski, P.; Tyszkiewicz, C.; Szponik, M.; Rogozi?ski, R.

2014-05-01

113

Hydrophobic self-cleaning surfaces of ZnO thin films synthesized by sol-gel technique Hydrophobic self-cleaning surfaces of ZnO thin films synthesized by sol-gel technique  

Microsoft Academic Search

This paper reported on highly transparent self-cleaning surfaces of zinc oxide synthesized via the sol-gel route. The results, including the x-ray diffraction, optical transmittance spectra, atomic force microscopy and the contact angles, were also reported in the paper, along with a discussion on the hydrophobic properties of zinc oxide. However, upon further investigation of the hydrophobicity of zinc oxide thin

S. Patra; S. Sarkar; S. K. Bera; R. Ghosh; G. K. Paul

2011-01-01

114

Distributed feedback dye-doped sol-gel silica lasers  

NASA Astrophysics Data System (ADS)

Solid state dye lasers with narrow linewidth and short pulse duration have attracted increasing attention because of their potential applications. Distributed feedback (DFB) laser is an effective compact coherent light source capable of tunable output with narrow linewidth. In this dissertation, lasing characteristics of dye doped sol-gel silica distributed feedback lasers have been investigated. The optical properties of sol-gel silica deduced from measurements of DFB laser output have also been studied. High optical homogeneity sol-gel silica slabs doped with desired concentration of Rhodamine 6G (MG), Coumarin 460 (C460), or Exalite 377E (E377) dye have been fabricated. Spatial periodic gain modulation in the dye doped sol-gel silica slab was created by crossing the diffracted pump beams from a holographic grating (1800 lines/mm) used as a beam splitter. Tunable laser emission in the yellow, the blue, and in the near ultraviolet region has been generated from the distributed feedback geometry using sol-gel silica slabs doped with R6G, C460 or E377 dye respectively. Wavelength tuning range of approximately 20 nm around the emission centers (562 nm, 480 nm, 376 nm) has been realized by varying the pump beams intersection angle. The laser linewidth was of the order of 60~80 pm when pump energy was several times over the threshold. Laser pulse trains with sub-nanosecond spikes were induced. A slope efficiency of approximately 4.5% has been obtained. The time behavior of distributed feedback R6G doped sol- gel silica laser has been studied using a N2 laser as the pump source. Sub-nanosecond pulse duration has been obtained. The pulse number in the output pulse train is sensitive to the pump energy. Experimental results of the time behavior are in good agreement with theoretical calculations. The lasing performance of tunable distributed feedback dye-doped sol-gel silica laser operating at different Bragg scattering order (M = 1, 2, 3) has also been studied. Distributed feedback laser operating at higher Bragg scattering order was observed at higher pump energy threshold and with lower energy conversion efficiency. The energy conversion efficiency of 0.7% (for M = 3) and 11% (for M = 2) has been achieved. Based on the Bragg scattering condition and the temperature dependence of the refractive index (?) of the gain medium, temperature tuning of the laser output was realized in experiment from the distributed feedback R6G doped sol-gel silica/PMMA lasers. Wavelength tuning from 573 nm to 556 mm has been demonstrated by varying the temperature from 21°C to 58°C. The laser linewidth was kept below 0.5 mm within the whole tuning range. The thermal coefficient of the emission wavelength has been measured. Finally the thermal coefficient of refractive index of sol-gel silica has been derived from these experimental data. Discontinuity in d?/dT curve attributable to phase transition has been observed in dye doped sol-gel silica slab and PMMA bulk. Temperature tuning performance of DFB laser using high temperature treated sol-gel silica as the gain medium has also been investigated.

Zhu, Xiaolei

115

Synthesis and characterisation of tantalum-incorporating silica hybrid sol–gel thin films for optical applications  

Microsoft Academic Search

A new acrylate-modified silica incorporating tantalum is synthesised via a sol–gel route. After deposition, the few micron-thick films can be photo-polymerised by UV-irradiation. FTIR spectroscopy gives a first insight into the curing process and the chemical structure of the hybrid material. The refractive index of the layers can be modulated by varying the concentration of tantalum in the material. Coatings

Danièle Blanc; Weiping Zhang; Christophe Massard; Jacques Mugnier

2006-01-01

116

A new approach to prepare nanoscopic rare earth metal fluorides: the fluorolytic sol-gel synthesis of ytterbium fluoride.  

PubMed

A new approach for the preparation of approx. 5 nm sized ytterbium fluoride nanoparticles based on the fluorolytic sol-gel route is reported. DLS, TEM, IR and XRD were used to characterize the particles as well as the aging behavior of the sols. Furthermore, a new Yb(III) complex was isolated from the precursor solution and characterized by X-ray single crystal structure determination. PMID:24824632

Schmidt, L; Dimitrov, A; Kemnitz, E

2014-06-25

117

Sol gel assisted ZnO nanorod array template to synthesize TiO2 nanotube arrays  

Microsoft Academic Search

A TiO2 nanotube array with a large surface area is fabricated on a glass substrate using a ZnO nanorod array and sol-gel process, and the structural characteristics of the TiO2 nanotube array are investigated. The well-aligned ZnO nanorod array, which is deposited on ZnO seed layer coated glass substrates by the wet-chemical route, is used as a template to synthesize

Jijun Qiu; Weidong Yu; Xiangdong Gao; Xiaomin Li

2006-01-01

118

Dynamics of Proteins Encapsulated in Silica Sol-Gel Glasses Studied with IR Vibrational Echo Spectroscopy  

E-print Network

Dynamics of Proteins Encapsulated in Silica Sol-Gel Glasses Studied with IR Vibrational Echo dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and -hemoglobin (HbCO) embedded in silica sol-gel structural dynamics experienced by a biomolecule. I. Introduction Proteins embedded in silica sol-gel glasses

Fayer, Michael D.

119

Sol-gel based alumina powders with catalytic applications  

NASA Astrophysics Data System (ADS)

The sol-gel process provides a new approach to the preparation of oxide materials and offers many advantages for making catalysts. Since homogeneous mixing can be achieved at the molecular scale, the chemical reactivity of the oxide surface can be greatly enhanced; thus powders with high surface area and optimized pore size distribution can be obtained at low temperatures. In the present work NiO/Al 2O 3 sol-gel catalysts were obtained by simultaneous gelation of aluminium isopropoxide and nickel nitrate. A comparative study with pure sol-gel alumina was also realized. By physical-structural studies the changes induced by the introduction of the Ni precursor, before and after aluminium alkoxide hydrolysis were highlighted. The introduction of Ni at the beginning of the reaction favors ?-Al 2O 3 crystallization. When Ni is added at the end of reaction, it delays the alumina crystallization and induces the disorder of the lattice. The obtained Ni doped sol-gel derived alumina has been used as catalyst in the finished form for glycerol reforming to generate H 2 for fuel cell applications. Some evaluation results of Ni-doped alumina combined with TiO 2 in photocatalytic glycerol reforming reaction have been included.

Cri?an, Maria; Zaharescu, Maria; Kumari, Valluri Durga; Subrahmanyam, Machiraju; Cri?an, Dorel; Dr?gan, Nicolae; R?ileanu, M?lina; Jitianu, Mihaela; Rusu, Adriana; Sadanandam, Gullapelli; Krishna Reddy, Jakkidi

2011-10-01

120

Sol-gel film formation by dip coating  

SciTech Connect

In this paper, the physical aspects of sol-gel film formation are discussed. The equations governing the steady state film profile, controlled by hydrodynamic flow, capillary pressure and evaporation, are presented along with representative data obtained by imaging ellipsometry. Some issues concerning capillary collapse are also addressed.

Hurd, A.J.; Brinker, C.J.

1990-01-01

121

ARSENIC REMOVAL USING SOL-GEL SYNTHESIZED TITANIUM DIOXIDE NANOPARTICLES  

EPA Science Inventory

In this study, the effectiveness of TiO2 nanoparticles in arsenic adsorption was examined. TiO2 particles (LS) were synthesized via sol-gel techniques and characterized for their crystallinity, surface area and pore volume. Batch adsorption studies were perf...

122

Sol-gel matrices for direct colorimetric detection of analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2000-01-01

123

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2002-11-26

124

Process of forming a sol-gel/metal hydride composite  

DOEpatents

An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

Congdon, James W. (Aiken, SC)

2009-03-17

125

New insights into uranium (VI) sol-gel processing  

SciTech Connect

Nuclear Magnetic Resonance (NMR) investigations on the Oak Ridge National Laboratory process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been extremely useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub 12}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sup 17}O NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, ((UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}){sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results will be presented to illustrate that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2} ((UO{sub 2}){sub 8} O{sub 4} (OH){sub 10}) {center dot} 8H{sub 2}O. This compound is the precursor to sintered UO{sub 2} ceramic fuel. 23 refs., 10 figs.

King, C.M.; Thompson, M.C.; Buchanan, B.R. (Westinghouse Savannah River Co., Aiken, SC (USA)); King, R.B. (Georgia Univ., Athens, GA (USA). Dept. of Chemistry); Garber, A.R. (South Carolina Univ., Columbia, SC (USA). Dept. of Chemistry)

1990-01-01

126

: comparison between magnetron sputtering and sol-gel synthesis  

NASA Astrophysics Data System (ADS)

SiGeO films have been produced by a sol-gel derived approach and by magnetron sputtering deposition. Post-thermal annealing of SiGeO films in forming gas or nitrogen atmosphere between 600 and 900 °C ensured the phase separation of the SiGeO films and synthesis and growth of Ge nanoclusters (NCs) embedded in SiO2. Rutherford backscattering spectrometry analysis evidenced a similar Ge concentration (~12 %), but a different Ge out-diffusion after annealing between the two types of techniques with the formation of a pure SiO2 surface layer (~30 nm thick) in sol-gel samples. The thermal evolution of Ge NCs has been followed by transmission electron microscopy and Raman analysis. In both samples, Ge NCs form with similar size increase (from ~3 up to ~7 nm) and with a concomitant amorphous to crystalline transition in the 600-800 °C temperature range. Despite a similar Ge concentration, a significant lower NCs density is observed in sol-gel samples attributed to an incomplete precipitation of Ge, which probably remains still dispersed in the matrix. The optical absorption of Ge NCs has been measured by spectrophotometry analyses. Ge NCs produced by the sol-gel method evidence an optical band gap of around 2 eV, larger than that of NCs produced by sputtering (~1.5 eV). These data are presented and discussed also considering the promising implications of a low-cost sol-gel based technique towards the fabrication of light harvesting devices based on Ge nanostructures.

Cosentino, S.; Knebel, S.; Mirabella, S.; Gibilisco, S.; Simone, F.; Bracht, H.; Wilde, G.; Terrasi, A.

2014-07-01

127

Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars  

NASA Technical Reports Server (NTRS)

Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report initial results on the production of sol-gel precursors for ceramic products using mineral resources available in martian or lunar soil. The presence of SO2, TiO2, and Al2O3 in both martian (44 wt.% SiO2, 1 wt.% TiO2, 7 wt.% Al2O3) and lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from lunar and martian soil simulars. Clear solutions of sol-gel precursors have been obtained by dissolution of silica from lunar soil similar JSC-1 in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Similarly, sol-gel solutions produced from martian soil simulars reveal higher contents of iron oxides. Characterization of the precursor molecules and efforts to further concentrate and hydrolyze the products to obtain gel materials will be presented for evaluation as ceramic precursors.

Sibille, L.; Gavira-Gallardo, J. A.; Hourlier-Bahloul, D.

2004-01-01

128

Protic ionic liquid as additive on lipase immobilization using silica sol-gel.  

PubMed

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The in?uence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss. PMID:23410924

de Souza, Ranyere Lucena; de Faria, Emanuelle Lima Pache; Figueiredo, Renan Tavares; Freitas, Lisiane dos Santos; Iglesias, Miguel; Mattedi, Silvana; Zanin, Gisella Maria; dos Santos, Onélia Aparecida Andreo; Coutinho, João A P; Lima, Álvaro Silva; Soares, Cleide Mara Faria

2013-03-01

129

Sol-Gel Synthesis of Fluoride Glasses and Thin Films: the Effects of Processing on the Chemical, Physical, Optical, and Rare Earth Fluorescence Properties of Sol - Zbla Glasses  

Microsoft Academic Search

Fluoride glasses have the potential to be ultra -low loss optical fiber and active optical devices due to their intrinsic clarity, wide transmission window, and low phonon energy. Unfortunately, conventional processing methods have failed to produce defect free glasses, fibers, or thin films. However, sol-gel techniques offer high purity, low temperature processing routes conducive to high quality optics. Thus, a

Matthew J. Dejneka

1995-01-01

130

Structural investigations of sol-gel-derived LiYF{sub 4} and LiGdF{sub 4} powders  

SciTech Connect

A soft synthesis route based on the sol-gel process was used for preparing rare-earth tetrafluoride powders from alkoxide precursors. In-situ fluorination was performed by decomposition of a fluorine containing organic compound named 1,1,1-trifluoro-5-methyl-2,4-hexanedione when sintering the as-prepared xerogel to produce crystallized samples. Both to insure complete departure of organic residues as well as to avoid any oxidation into oxyfluoride, annealing treatment was carried out under fluorine atmosphere. Free-oxygen content of resulting samples was evidenced by infrared and Raman spectroscopies. X-ray absorption spectroscopies (XAS) and {sup 19}F nuclear magnetic resonance (NMR) studies showed that samples heat treated at 300 deg. C are already crystallized but for a full crystallization in LiGdF{sub 4} and LiYF{sub 4} a thermal treatment at 550 deg. C is needed. Temperature dependence of powder morphology was analyzed by scanning electron microscopy (SEM). - Graphical abstract: The sol-gel route is a soft process, which allows developing versatile-shaped compounds. A fluorine organic compound named 1,1,1-trifluoro-5-methyl-2,4-hexadione was used to synthesis LiGdF{sub 4} and LiYF{sub 4} powders based on the sol-gel method. These materials can be used as host lattices for rare-earth ions to provide phosphors.

Lepoutre, S. [Laboratoire des Materiaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal et Ecole Nationale Superieure de Chimie de Clermont-Ferrand, 24 Avenue des Landais, 63177 Aubiere cedex (France); Boyer, D. [Laboratoire des Materiaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal et Ecole Nationale Superieure de Chimie de Clermont-Ferrand, 24 Avenue des Landais, 63177 Aubiere cedex (France)], E-mail: damien.boyer@univ-bpclermont.fr; Potdevin, A.; Dubois, M. [Laboratoire des Materiaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal et Ecole Nationale Superieure de Chimie de Clermont-Ferrand, 24 Avenue des Landais, 63177 Aubiere cedex (France); Briois, V. [Synchrotron SOLEIL, L'Orme des Merisiers, BP48, 91192 Gif-sur-Yvette Cedex (France); Mahiou, R. [Laboratoire des Materiaux Inorganiques, CNRS UMR 6002, Universite Blaise Pascal et Ecole Nationale Superieure de Chimie de Clermont-Ferrand, 24 Avenue des Landais, 63177 Aubiere cedex (France)

2007-11-15

131

Morphology evolution of ZrB{sub 2} nanoparticles synthesized by sol-gel method  

SciTech Connect

Zirconium diboride (ZrB{sub 2}) nanoparticles were synthesized by sol-gel method using zirconium n-propoxide (Zr(OPr){sub 4}), boric acid (H{sub 3}BO{sub 3}), sucrose (C{sub 12}H{sub 22}O{sub 11}), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C{sub 12}H{sub 22}O{sub 11} was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB{sub 2} particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB{sub 2} were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB{sub 2} related to the gelation temperature obeyed the 'oriented attachment mechanism' of crystallography. - Graphical Abstract: Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. Highlights: > ZrB{sub 2} nanoparticles were synthesized by sol-gel method in an non-aqueous solution system. > AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. > C{sub 12}H{sub 22}O{sub 11} was selected since it can be completely decomposed to carbon. > Increasing the gelation temperature, the particles changed from sphere-like to rod-like ones. > Crystalline nature of ZrB{sub 2} obeyed the 'oriented attachment mechanism' of crystallography.

Zhang Yun [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li Ruixing, E-mail: ruixingli@yahoo.com [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Jiang Yanshan; Zhao Bin; Duan Huiping [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li Junping; Feng Zhihai [Aerospace Research Institute of Materials and Processing Technology, Beijing 100076 (China)

2011-08-15

132

Second-harmonic generation from sol-gel-derived ferroelectric and piezoelectric thin films  

NASA Astrophysics Data System (ADS)

Sol-gel routes were developed to Ba2NaNb5O15, BaTiO3, Ba0.8Pb0.2TiO3, Ba0.8Sr0.2TiO3, Bi4Ti3O12, LiNbO3, LiTaO3, Pb5Ge3O11, PbTiO3, Pb0.85La0.15Ti0.96O3, PbZr0.2Ti0.8O3, WO3 and ZnO thin films. Second harmonic generation (SHG) from these films deposited on fused SiO2 was investigated as a function of processing temperature. The SHG values were found to be related to the second-order nonlinear optical susceptibilities of the bulk materials, and dependent on the crystal size and crystalline orientation of the film. The highest SHG observed was from PbTiO3 films which is consistent with the fact that the d-coefficient of PbTiO3 is the highest among that of any room temperature ferroelectric. The poor SHG activity of BaTiO3-based films was due to the very small grain size of the sol-gel derived material.

Boulton, J. M.; Teowee, Gimtong T.; Bommersbach, W. M.; Uhlmann, Donald R.

1992-12-01

133

Optical detection of parasitic protozoa in sol-gel matrices  

NASA Astrophysics Data System (ADS)

Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

1994-10-01

134

Tunable Optical Properties of Metal Nanoparticle Sol-Gel Composites  

NASA Technical Reports Server (NTRS)

We demonstrate that the linear and non-linear optical properties of sol-gels containing metal nanoparticles are highly tunable with porosity. Moreover, we extend the technique of immersion spectroscopy to inhomogeneous hosts, such as aerogels, and determine rigorous bounds for the average fractional composition of each component, i.e., the porosity of the aerogel, or equivalently, for these materials, the catalytic dispersion. Sol-gels containing noble metal nanoparticles were fabricated and a significant blue-shift in the surface plasmon resonance (SPR) was observed upon formation of an aerogel, as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping and aggregation this blue-shift does not strictly obey standard effective medium theories. Mitigation of these complications is achieved by avoiding the use of alcohol and by annealing the samples in a reducing atmosphere.

Smith, David D.; Snow, Lanee A.; Sibille, Laurent; Ignont, Erica

2001-01-01

135

Sol-gel synthesis and characterization of yttrium gallium garnets  

NASA Astrophysics Data System (ADS)

Precursor powders for yttrium gallium garnet (Y3Ga5O12, YGG) were prepared by a simple sol-gel method based on the formation of metal chelates in aqueous solvents. A systematic study of sol-gel technique synthesized YGG samples is presented using different complexing agents. Six high-purity organic substances were used as complexing agents, namely, tartaric acid, 1,2-ethanediol, citric acid, ethylene diamine tetra-acetic acid (EDTA), malonic acid, and oxalic acid. These agents were found to influence the characteristics of the end products, in particular their homogeneity. The phase purity, composition, and microstructure of the polycrystalline samples were studied by thermoanalytical methods (TGADTA), x-ray diffraction (XRD) analysis, IR spectroscopy, and scanning electron microscopy (SEM). From the typical XRD patterns of different synthesis products it is concluded that only the use tartaric acid, 1,2-ethanediol, citric acid, and EDTA yields a single YGG phase.

Leleckaite, Asta; Urbonaite, Sigita; Tõnsuaadu, Kaia; Kareiva, Aivaras

2005-08-01

136

Sol-Gel-Derived Hybrid Coatings for Corrosion Protection  

Microsoft Academic Search

The corrosion resistance of sol-gel-derived, organic-inorganic, silica-based hybrid coatings was studied. Hybrid sols were prepared by copolymerizing tetraethylorthosilicate (TEOS) and 3-methacryloxypropyltrimethoxysilane (MPS) with a two-step acid-catalyst process. Hybrid coatings were dip-coated on 304 and 316 stainless steel substrates and annealed at 300°C for 30 minutes. The adhesion, flexibility, and biocompatibility of the coatings were examined. Hybrid coatings were found to

T. P. Chou; C. Chandrasekaran; G. Z. Cao

2003-01-01

137

Novel thermochromism in silica sol-gel materials  

Microsoft Academic Search

In this contribution we provide evidence for thermochromic color changes unique to silica based materials formed at low temperatures by the sol-gel process. The materials formed have potential application as temperature sensitive light filters, visual temperature indicators, self-diagnostic labels for electronic devices and IR recording media. The dopants, diamine complexes of copper(II)\\/nickel(II) chloride, change from purple to green following heating

Martin Gardener; Carole C. Perry

2000-01-01

138

Sol–gel hydroxyapatite coatings on stainless steel substrates  

Microsoft Academic Search

Thin film hydroxyapatite deposits onto sandblasted 316L stainless steel substrates were prepared using water-based sol–gel technique recently developed in our lab. The coatings were annealed in air at 375°C, 400°C, and 500°C. Phase formation, surface morphology, interfacial microstructure, and interfacial bonding strength of the coatings were investigated. Apatitic structure developed within the coatings while, annealing at temperatures ?400°C, while those

Dean-Mo Liu; Quanzu Yang; Tom Troczynski

2002-01-01

139

Control of rehydration in sol-gel glasses  

Microsoft Academic Search

Optical properties of monoliths synthesized via the sol gel process result in a large number of residual silanol (Si-OH) groups, even after annealing at 900 C. High silanol content quenches emission from rare earth ions via excitation of vibrations of the silanol groups. Medium density glasses (1.5gcm-3) have a highly interconnected porous structure that allows the diffusion of molecules throughout

Carlos Ortiz; Daniel Boye

2007-01-01

140

Erbium in photosensitive hybrid organoaluminosilicate sol-gel glasses  

Microsoft Academic Search

Microstructural features of a new hybrid organoaluminosilicate glass are described. The glass is prepared by low temperature acid catalyzed hydrolysis and polycondensation of organoalkoxides. This sol-gel method produces transparent materials for one-step, crack-free thin film formation suitable for fabrication of passive and active optical waveguides. Aluminum NMR reveals that the inclusion of erbium ions affects the structure of the glass

Galina Milova; S. Iraj Najafi; A. Skirtach; David J. Simkin; Mark P. Andrews

1997-01-01

141

Sol-Gel Synthesized Adsorbents for Metal Separation  

Microsoft Academic Search

A series of organo-ceramic adsorbents have been synthesized by a sol-gel processing technique for metal ion extraction. These adsorbents generally have significantly high metal uptake capacities, good physical-chemical stabilities, and well-designed pore geometries compared to other pre-existing metal-chelating ceramic-based adsorbents. This work describes the synthesis and evaluation of pyrazole and calix[4]arene crown adsorbents for selective separation of platinum, palladium, and

L.L. Tavlarides; J. S. Lee; K. H. Nam; N. Agarwal

2006-01-01

142

Replication of optical MEMS structures in sol–gel materials  

Microsoft Academic Search

A replication method of fabrication for micro electro mechanical systems (MEMS) structures is presented, for use as an alternative to silicon processing. UV-curable ORMOCER® sol–gel is used as base material. The basic fabrication process involves deposition and patterning of a sacrificial spacer layer and a combined molding and photolithography step. This method allows creation of free-standing micro-mechanical elements with monolithic

S. Obi; M. T. Gale; A. Kuoni; N. De Rooij

2004-01-01

143

Synthesis of zirconium oxide nanoparticle by sol-gel technique  

SciTech Connect

Zirconium oxide nanoparticle is synthesized using sol-gel technique. Various mole ratio of ammonia solution and nitric acid relative to zirconium propoxide is added in the reaction to study the effect on the crystallinity and particle size on zirconium oxide particle. Zirconium oxide synthesized with nitric acid have the smallest particle size under FESEM image and show the increasing formation of crystalline tetragonal phase under XRD diffractogram.

Lim, H. S.; Ahmad, A.; Hamzah, H. [School of Chemical Science and Food Technology, Faculty of Science and Technology, National University of Malaysia, 43600 Bangi (Malaysia)

2013-11-27

144

Molecular forms of coumarin-307 in sol-gel glasses.  

PubMed

Coumarin-307(C-307) impregnated sol-gel glass samples were prepared by two methods - (I) predoping using HNO3 as catalyst, and (II) postdoping using HNO3 as catalyst and formamide as drying control chemical additive (DCCA). The absorption/fluorescence properties including fluorescence lifetime of the dye in these sol-gel host matrices were studied and results were compared with dye in methanol (MeOH). In addition to usual non-polar form of C-307 that exists in MeOH, amino-protonated form and dimer of dye have also been found to co-exist in the dried state of samples prepared by predoping method. This behaviour of dye was uncommon to sol and gel states of materials. The fluorescence quantum yield (Qf) of C-307 doped solid was found to be 0.77 and it was almost constant in the concentration range 5 x 10(16) to 8.8 x 10(17) cm(-3). On the other hand, only non-polar form of C-307 has been observed in the samples prepared by postdoping method. The Qf value of dye was 0.96 in the postdoped samples. To explain such behaviour of C-307 in the two types of sol-gel matrices: dye concentration, role of HNO3, water, formamide and matrix effect have been taken into account. PMID:16933143

Deshpande, Aparna V; Kumar, Uday

2006-09-01

145

Sol-gel Technology and Advanced Electrochemical Energy Storage Materials  

NASA Technical Reports Server (NTRS)

Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

Chu, Chung-tse; Zheng, Haixing

1996-01-01

146

Comparative study of nanocrystalline titanium dioxide obtained through sol-gel and sol-gel-hydrothermal synthesis.  

PubMed

TiO2 particles were prepared by sol-gel method alone and by sol-gel method combined with hydrothermal treatment. The structural and photocatalytic properties of the two series of photocatalysts were compared. XRD studies revealed that rutilization was faster in the series of photocatalysts, which had been additionally subjected to a hydrothermal process (SG-HT). The hydrothermally treated photocatalysts also displayed a higher specific surface area than those which had only been synthesized using the sol-gel process (SG) and subjected to low calcination temperatures of up to 873 K, while this tendency was inverted at higher temperatures. In accordance with the above observation, the hydrothermally treated series of photocatalysts had a lower particle size than the SG series calcined immediately after the sol-gel process up to 873 K, with this relation being inverted for the highest two temperatures which were studied (973 K and 1023 K) and which saw the commencement of rutilization. Increases in average particle size were observed for both series, with a polyhedral morphology seen as calcination temperature rose. FTIR studies highlighted the presence of the band at 2351 cm(-1) in the SG-HT photocatalysts, characteristic of surface-adsorbed CO2. This was not seen in the SG or P25 photocatalysts. In terms of photoreactivity, the best photocatalyst in the SG-HT series was that calcined at 923 K and in the SG series at 1023 K (SG-1023). Comparing these two photocatalysts and the commercial P25 photocatalyst, SG-1023 was found to be the most photoactive in both the photodegradation and the mineralization of phenol. PMID:23582907

Seck, E I; Doña-Rodríguez, J M; Pulido Melián, E; Fernández-Rodríguez, C; González-Díaz, O M; Portillo-Carrizo, D; Pérez-Peña, J

2013-06-15

147

Morphology evolution of ZrB 2 nanoparticles synthesized by sol-gel method  

NASA Astrophysics Data System (ADS)

Zirconium diboride (ZrB 2) nanoparticles were synthesized by sol -gel method using zirconium n-propoxide (Zr(OPr) 4), boric acid (H 3BO 3), sucrose (C 12H 22O 11), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr) 4 hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C 12H 22O 11 was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB 2 particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 °C to a particle chain at 75 °C, and then form rod-like particles at 85 °C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB 2 were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB 2 related to the gelation temperature obeyed the "oriented attachment mechanism" of crystallography.

Zhang, Yun; Li, Ruixing; Jiang, Yanshan; Zhao, Bin; Duan, Huiping; Li, Junping; Feng, Zhihai

2011-08-01

148

Amperometric hydrogen peroxide biosensor with sol–gel\\/chitosan network-like film as immobilization matrix  

Microsoft Academic Search

A new type of sol–gel\\/organic hybrid composite material based on the cross-linking of natural polymer chitosan with (3-aoryloxypropyl) dimethoxymethylsilane was developed for the fabrication of an amperometric H2O2 biosensor. The composite film was used to immobilize horseradish peroxidase (HRP) on a gold disk electrode. The properties of sol–gel\\/chitosan and sol–gel\\/chitosan-HRP films have been carefully characterized by atomic force microscopy and

Gang Wang; Jing-Juan Xu; Hong-Yuan Chen; Zu-Hong Lu

2003-01-01

149

Multiparameter evaluation of fast sol–gel process by terahertz measurements  

Microsoft Academic Search

We present a feasibility study to apply terahertz (THz) spectroscopy and THz imaging as non-destructive diagnostic tools for\\u000a sol–gel analysis, manufacturing and quality control. By performing THz spectroscopy on liquid and solid samples we were able\\u000a to follow several key parameters during the sol–gel formation process and of the final product. Sol–gel transformations were\\u000a monitored by THz absorption, whereas density

Raz Gvishi; Avraham Englander; Gadi Peleg

2008-01-01

150

Novel inorganic\\/organic hybrid materials based on blown soybean oil with sol–gel precursors  

Microsoft Academic Search

New ceramer coatings based on blown soybean oil with sol–gel precursors were prepared and evaluated as a function of the blowing process and sol–gel precursors content. Soybean oils were blown at three different rates in order to optimize the blowing process. Three sol–gel precursors, titanium (IV) i-propoxide, titanium (IV) di-i-propoxide bis-acetoacetonate, and zirconium n-propoxide were then used with the blown

Ganghua Teng; Joseph R Wegner; Greta J Hurtt; Mark D Soucek

2001-01-01

151

Second-harmonic generation from sol-gel-derived ferroelectric and piezoelectric thin films  

Microsoft Academic Search

Sol-gel routes were developed to Ba2NaNb5O15, BaTiO3, Ba0.8Pb0.2TiO3, Ba0.8Sr0.2TiO3, Bi4Ti3O12, LiNbO3, LiTaO3, Pb5Ge3O11, PbTiO3, Pb0.85La0.15Ti0.96O3, PbZr0.2Ti0.8O3, WO3 and ZnO thin films. Second harmonic generation (SHG) from these films deposited on fused SiO2 was investigated as a function of processing temperature. The SHG values were found to be related to the second-order nonlinear optical susceptibilities of the bulk materials, and dependent

J. M. Boulton; Gimtong T. Teowee; W. M. Bommersbach; Donald R. Uhlmann

1992-01-01

152

Lead ion-selective electrode prepared by sol–gel and PVC membrane techniques  

Microsoft Academic Search

Sol–gel electrode and coated-wire ion-selective electrode (CWISE) based on Schiff base as a neutral carrier, was successfully developed for detection of Pb(II) in aqueous solution.The sol–gel and CWISE exhibited linear response with Nernstian slope of 29.1 and 28.9mV\\/decade, respectively, within the concentration ranges of 5.0×10?6 to 1.0×10?1molL?1 lead ion for sol–gel and coated. The sol–gel and CWISE has shown detection

M. Mazloum Ardakani; M. Khayat Kashani; M. Salavati-Niasari; A. A. Ensafi

2005-01-01

153

Sol Gel-Derived SBA-16 Mesoporous Material  

PubMed Central

The aim of this article is to review current knowledge related to the synthesis and characterization of sol gel-derived SBA-16 mesoporous silicas, as well as a review of the state of the art in this issue, to take stock of knowledge about current and future applications. The ease of the method of preparation, the orderly structure, size and shape of their pores and control, all these achievable through simple changes in the method of synthesis, makes SBA-16 a very versatile material, potentially applicable in many areas of science and molecular engineering of materials. PMID:20957080

Rivera-Munoz, Eric M.; Huirache-Acuna, Rafael

2010-01-01

154

Epitaxial Growth of Yb2O3 Buffer Layers on Biaxially Textured-Ni (100) Substrates by Sol-Gel Process  

SciTech Connect

In order to develop an alternative buffer layer architecture using the sol-gel process to produce YBCO (YBa2Cu307+) coated conductors, Yb203 has been chosen as the candidate material. Buffer layers of fi03 were epitaxkdly grown on biaxially textured-Ni (100) substrates by the sol gel process for the first time. The ~03 precursor solution was prepared from an alkoxide sol-gel route in 2-xnetho~ethanol and was deposited on textured-Ni (100) substrates by either spin coating or dip coating methods. The amorphous film was then processed at 1160oC under flowing (96%)MH2(4%) gas mixture for one hour. The fi03 iihn exhibited a strong c-axis orientation on the Ni (100) substrates. The phi and omega scans indicated good in plane and out of plane orientations. The X-ray (222) pde figure showed a cube-on-cube epitaxy. High current YBCO films were grown on the Y&03 sol-gel buffered-Ni substrates.

Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Feenstra, R.; Goyal, A.; Kroeger, D.M.; Lee, D.F.; Martin, P.M.; Morrell, J.S.; Paranthaman, M.; Sun, E.Y.; Verebelyi, D.T.; Williams, R.K.

1999-04-05

155

Hydrophobic self-cleaning surfaces of ZnO thin films synthesized by sol-gel technique Hydrophobic self-cleaning surfaces of ZnO thin films synthesized by sol-gel technique  

NASA Astrophysics Data System (ADS)

This paper reported on highly transparent self-cleaning surfaces of zinc oxide synthesized via the sol-gel route. The results, including the x-ray diffraction, optical transmittance spectra, atomic force microscopy and the contact angles, were also reported in the paper, along with a discussion on the hydrophobic properties of zinc oxide. However, upon further investigation of the hydrophobicity of zinc oxide thin films, we found that the contact angles originally reported were not reproducible, and hence this might have led to incorrect and ambiguous analysis of the properties of zinc oxide thin films. The inconsistency in the data and the ambiguities oblige the authors to retract the above article.

Patra, S.; Sarkar, S.; Bera, S. K.; Ghosh, R.; Paul, G. K.

2011-07-01

156

Manipulation and characterization of thin-film interfacial chemistry: Sol-gel deposition and single molecule tracking experiments  

NASA Astrophysics Data System (ADS)

Single molecule trajectories of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbo - cyanine perchlorate (DiI) fluorophores diffusing on planar supported 1,2-dimyristoyl-snglycero- 3-phosphocholine (DMPC) lipid bilayers imaged through total internal reflection fluorescence (TIRF) microscopy at different temperatures are investigated. The spatial resolution limit for detecting molecular motion is evaluated by characterizing the apparent motion which arises from the limited signal-to-noise ratio (S/N) of imaged and simulated stationary DiI molecules. Statistical criteria for reliably distinguishing molecular motion from stationary molecules using F-test statistics, including the computation of local signal-to-noise ratios are then established and used for reliably detecting subdiffraction motion of DiI molecules on DMPC. The same single molecule tracking concept is used in investigating the temperature dependence of subdiffraction diffusional confinement of single Rhodamine 6G molecules in polymer brushes of poly (N-isopropylacrylamide), pNIPAAm, above and below its lower critical solution temperature (LCST) of 32°C. Reliably distinguishing subdiffraction molecular motion from stationary events is crucial in validating the application of single molecule tracking experiment in probing nanometersized hydrophobic environments of polymer structure. A versatile and rapid sol-gel technique for the fabrication of high quality one-dimensional photonic bandgap materials was developed. Silica/titania multilayer materials are fabricated by a sol-gel chemistry route combined with dip-coating onto planar or curved substrate. A shock-cooling step immediately following the thin film heat-treatment process is introduced. The versatility of this sol-gel method is demonstrated by the fabrication of various Bragg stack-type materials with fine-tuned optical properties. Measured optical properties show good agreement with theoretical simulations confirming the high quality of these sol-gel fabricated optical materials. Finally, magnetic functionalization studies of sol-gel derived Co-ion doped titania thin films using superconducting quantum interference device (SQUID) magnetometry and an attempt to measure their magneto-optical properties using a home-built Faraday rotation setup are discussed. The experimental limitations in reliably measuring magnetization responses of these thin films are introduced and discussed in detail. The summary and outlook chapters summarize the scientific significance of each research project and briefly introduce ongoing research based on the work and the results presented in this dissertation.

Barhoum, Moussa

157

Influence of processing parameters on the luminescence of sol-gel derived PrPO{sub 4}  

SciTech Connect

PrPO{sub 4} synthesis by the sol-gel process was carried out using an alkoxide route. Powders purity and morphology were analyzed by means of X-ray diffraction, laser granulometry and scanning electron microscopy. Moreover, praseodymium fluorescence in that lattice was recorded by laser induced spectroscopy at room temperature. Upon excitation into the {sup 3}P{sub 0} high energy level, emission in the red wavelength range is observed from this state as well as from the {sup 1}D{sub 2} level. Finally, dependence of the phosphorus precursor and hydrolysis rate on the quantum efficiency was investigated.

Chadeyron-Bertrand, G. [Laboratoire des Materiaux Inorganiques UMR 6002 CNRS, Universite Blaise Pascal and ENSCCF, 24 Avenue des Landais, 63177 Aubiere Cedex (France)]. E-mail: chadeyr@chimtp.univ-bpclermont.fr; Vial, S. [Laboratoire des Materiaux Inorganiques UMR 6002 CNRS, Universite Blaise Pascal and ENSCCF, 24 Avenue des Landais, 63177 Aubiere Cedex (France); Cellier, J. [Laboratoire des Materiaux Inorganiques UMR 6002 CNRS, Universite Blaise Pascal and ENSCCF, 24 Avenue des Landais, 63177 Aubiere Cedex (France); Boyer, D. [Laboratoire des Materiaux Inorganiques UMR 6002 CNRS, Universite Blaise Pascal and ENSCCF, 24 Avenue des Landais, 63177 Aubiere Cedex (France); Mahiou, R. [Laboratoire des Materiaux Inorganiques UMR 6002 CNRS, Universite Blaise Pascal and ENSCCF, 24 Avenue des Landais, 63177 Aubiere Cedex (France)

2005-09-01

158

Optimization of sol-gel synthesis of CoFe2O4 nanowires using template assisted vacuum suction method  

NASA Astrophysics Data System (ADS)

In this study, cobalt ferrite nanowires were synthesized by a sol-gel route using anodized aluminum oxide (AAO) template by applying mechanical vacuum suction. The parameters of calcination temperature and pH value were optimized subsequently. The single phase cobalt ferrite was obtained at 600 °C. The results showed that pH=1 is appropriate for synthesis of uniform nanowires because at the higher pH values the autocombustion of the gel, with making cracks in nanowires, will be happened. Furthermore, the nanowires showed higher coercivity in the direction parallel to the axis of the nanowires (Hc?=1050 Oe) rather than that in the perpendicular direction (Hc?=772 Oe).

Pirouzfar, A.; Seyyed Ebrahimi, S. A.

2014-12-01

159

Index modulation Bragg gratings directly imprinted on sol gel layers  

NASA Astrophysics Data System (ADS)

Among the fabrication techniques of integrated optical devices, the sol-gel chemistry is now performant enough to make thin films of transparent materials with controlled purity and composition, at low temperature. Semi-mineral semi-organic solutions allow dip coating followed by low temperature baking to deposit vitreous films up to eight micrometers thick which are free from cracks. A local polymerization process through UV exposure enables hybrid components compatible with electronic planar silicon or III- V components. This UV imprinting method is used here to make index modulation gratings with use of a holographic equipment as an alternative to the use of a costly phase mask. Gratings have been imprinted on various sol-gel films; single layer, with a protective coating, and/or with an isolating buffer layer from the substrate, which is silicon and glass. Diffraction magnitude is measured in the various cases, as well as analysis and computer simulations are performed. Wavelength filters are experimented and studied. This shows the potential of this low cost technology in integrated optics, for application in telecommunications.

Moreau, Yves; Arguel, Philippe; Coudray, Paul; Porque, Jerome; Etienne, Pascal

1998-01-01

160

Novel thermochromism in silica sol-gel materials  

NASA Astrophysics Data System (ADS)

In this contribution we provide evidence for thermochromic color changes unique to silica based materials formed at low temperatures by the sol-gel process. The materials formed have potential application as temperature sensitive light filters, visual temperature indicators, self-diagnostic labels for electronic devices and IR recording media. The dopants, diamine complexes of copper(II)/nickel(II) chloride, change from purple to green following heating to 100 degrees C and revert to purple on cooling in the atmosphere. This color change has been explained by the substitution of water molecules by chloride ions in the first coordination sphere of the metal ions. When the same compounds are incorporated into a silica sol-gel matrix under acidic conditions the gel-glasses may be pale green, dark green, yellow, olive-yellow, blue or brown depending on the metal ion chosen and the extent of thermal treatment. Studies on the complexes themselves and on granular silicas doped with some of the complexes are assisting us in understanding the molecular mechanisms that give rise to these color changes.

Gardener, Martin; Perry, Carole C.

2000-05-01

161

Nanostructured Energetic Materials with Sol-Gel Methods  

SciTech Connect

The utilization of sol-gel chemical methodology to prepare nanostructured energetic materials as well as the concepts of nanoenergetics is described. The preparation and characterization of two totally different compositions is detailed. In one example, nanostructured aerogel and xerogel composites of sol-gel iron (III) oxide and ultra fine grained aluminum (UFG Al) are prepared, characterized, and compared to a conventional micron-sized Fe{sub 2}O{sub 3}/Al thermite. The exquisite degree of mixing and intimate nanostructuring of this material is illustrated using transmission and scanning electron microscopies (TEM and SEM). The nanocomposite material has markedly different energy release (burn rate) and thermal properties compared to the conventional composite, results of which will be discussed. Small-scale safety characterization was performed aerogels and xerogels of the nanostructured thermite. The second nanostructured energetic material consists of a nanostructured hydrocarbon resin fuel network with fine ammonium perchlorate (NH{sub 4}ClO{sub 4}) oxidizer present.

Gash, A; Satcher, J; Simpson, R; Clapsaddle, B

2003-11-25

162

Optical materials by a modified sol-gel nanoparticle process  

NASA Astrophysics Data System (ADS)

Optical sol-gel materials have been of interest for many years. The reason is that through the preparation of sold with nanoparticulate liquid structures, transparent coatings of many inorganic oxides can be produced. By using oxides for example, with different refractive indices, reflective or antireflective coatings can be fabricated. To obtain stable layers, the gel coating have to be densified at higher temperatures, in general between 400 and 600 degrees C. This may be suitable for glass surfaces, but not for temperature sensitive substrates like plastics. In addition to this, if multilayer coatings have to be produced, between each step a densification process has to be carried out before the net coating step takes place. This leads to an unsatisfying situation if industrial low cost processing is required. In addition to this, the dip coating process is not suitable for high speed or large area coating techniques. This is one of the reasons whey the sol-gel process never has gained a real high significance for industrial coatings on glass and is limited to special products so far.

Schmidt, Helmut K.; Mennig, Martin

2000-05-01

163

Electrospun sol-gel fibers for fluorescence-based sensing  

NASA Astrophysics Data System (ADS)

Fluorescence based biosensors have the ability to provide reliable pathogen detection. However, the performance could be improved by enhancing the effective surface area of the biosensor. We report on a new nanofibrous fluorescencebased biosensor, whereas a sol-gel platform mesh was constructed by utilizing electrospinning techniques. Furthermore, incorporating cetyltrimethylammonium bromide (CTAB) and conducting pore-forming techniques resulted in a high surface area material suitable for biosensor immobilization. The biosensor was designed to detect Helicobacter hepaticus bacterium by sandwiching the pathogen between two antibodies, one labeled with Alexa Fluor 546 fluorescent dye and the other with 20nm Au nanoparticles. In the presence of pathogen, the close proximity of Au nanoparticles quenched the Alexa Fluor fluorescence, suggesting that the electrospun fiber platforms are suitable for sensing H. Hepaticus. Additionally, sol-gel fibers used as biosensor platform have the added benefit of increased immobilization, as fluorescence intensity from immobilized biosensors is 8.5x106 cps higher on fibers than on a flat, non-porous substrate.

Memisevic, Jasenka; Riley, Lela; Grant, Sheila A.

2009-05-01

164

Suppression of arsenopyrite surface oxidation by sol-gel coatings.  

PubMed

Oxidation of arsenopyrite (FeAsS) in mine tailings is considered as the major cause of arsenic release in groundwater around mineral mine sites. Oxidation rate is increased by the biooxidation of chemolithoautotrophic bacteria, such as Acidithiobacillus ferrooxidans via the adsorption mechanism. Hence, coating with thin films as a physical barrier for oxidants surrounding the mineral surface is one of the effective abatement strategies. In this work, we studied and characterized the formation of thin films using sol-gel on arsenopyrite and investigated the resistance of thin films to biological and chemical oxidations. We selected methyltrimethoxysilane (MTMOS), tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (AAPS) as sol-gel precursors. MTMOS coating arsenopyrite particles at a H2O/Si molar ratio of 2 suppressed both biological oxidation and chemical oxidation and was superior to other alkoxysilane monomers. Factors involved in oxidation suppression are the crack-free morphology and the hydrophobicity of MTMOS coating. The Si-O-Si spectrum by Fourier transform infrared (FTIR) distinctly found for the MTMOS film is considered to indicate the formation of the networks of the film, and the Fe-O-Si spectrum confirmed the bonding of the film to the arsenopyrite surface. PMID:16233789

Khummalai, Nitinai; Boonamnuayvitaya, Virote

2005-03-01

165

Titanium (IV) sol-gel chemistry in varied gravity environments  

NASA Astrophysics Data System (ADS)

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. The test systems and experimental results obtained will be presented. 1. Okubo, T., Tsuchida, A., Okuda, T., Fujitsuna, K., Ishikawa, M., Morita, T., Tada, T. , Kinetic Analyses of Colloidal Crystallization in Microgravity -Aircraft Experiments. . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999. 153: p. 515-524. 2. Okubo, T., Tsuchida, A., Kobayashi, K., Kuno, A., Morita, T., Fujishima, M., Kohno, Y., Kinetic Study of the Formation Reaction of Colloidal Silica Spheres in Microgravity Using Aircraft. Colloid Polymer Science, 1999. 277(5): p. 474-478. 3. Pienaar, C.L., Chiffoleau, G. J. A., Follens, L. R. A., Martens, J. A., Kirschhock, C. E. A., Steinberg, T. A., Effect of Gravity on the Gelation of Silica Sols. Chem. Mater., 2007. 19(4): p. 660-664. 4. Smith, D.D., et al., Effect of Microgravity on the Growth of Silica Nanostructures. Langmuir, 2000. 16(26): p. 10055-10060. 5. Zhang, X., Johnson, D.P., Manerbino, A.R., Moore, J.J., Schowengerdt, F. , Recent Mi-crogravity Results in the Synthesis of Porous Materials. AIP Conference Proceedings (Space Technology and Applications International Forum-1999, Pt. 1), 1999. 458: p. 88-93. 6. Dunbar, P.B., Bendzko, N.J.,, 1H and 13C NMR observation of the reaction of acetic acid with titanium isopropoxide. Materials Chemistry and Physics, 1999. 59: p. 26-35. 7. Krunks, M., Oja, I., T˜nsuaadu, K., Es-Souni, M., Gruselle, M., Niinistü,. L, Thermoanalytical study of acetylacetonate-modified titanium (iv) isopropoxide as precursor for TiO2 films. Journal of Thermal Analysis and Calorimetry, 2005: p. 483-488. 8. Moran, P.D., Bowmaker, G. A., Cooney, R. P., Vibrational Spectra and Molecular Associa-tion of Titanium Tetraisopropoxide. Inorg. Chem., 1998. 37(1): p. 2741-2748. 9. Somogyvari, A., Serpone, N.,, Evidence for five-coordination in titanium(1V) complexes. A nuclear magnetic resonance investigation. Canadian Journal of Chemistry, 1977. 56: p. 316-319.

Hales, Matthew; Martens, Wayde; Steinberg, Theodore

166

Transpiration cooled ultraviolet sol-gel silica optics  

NASA Astrophysics Data System (ADS)

All rocket guidance systems essentially require broadband optical transmission windows. These windows must also be temperature insensitive to transmission, thermal shock resistant, thermally stable, reasonably strong, and impact resistant. At hypersonic velocity, convective cooling is preferred to radiative cooling. Transpiration cooling is a novel and effective mode of convective cooling. Porous silica windows offer excellent rocket windows for transpiration cooling at a relatively inexpensive price. Sol-gel technology is an enabling technology which facilitates the fabrication of these rocket windows. This research used sol-gel technology to demonstrate the concept of transpiration-cooled porous silica windows. These windows were fabricated with various pore sizes and characterized with respect to gas diffusion, transpiration, high temperature transmission, thermal stability and shock resistance, hardness, impact resistance, and strength. The manufacturability aspect was also addressed. The diffusion of various gases through porous silica windows was studied and their permeabilities measured. In the experimental range, Knusden diffusion seemed to be the predominant mass transport mechanism. At a low transpiration velocity of 0.52 cm/s of helium, a 44 C temperature drop was observed showing the promise of this material for rocket window application. High temperature spectroscopy showed improved performance. The porous silica windows had thermal stability and thermal shock resistance and reasonable mechanical properties.

Seth, Vinay K.; Noques, Jean-Luc

1991-04-01

167

Bactericidal micron-thin sol-gel films prevent pin tract and periprosthetic infection.  

PubMed

Orthopedic injuries constitute the majority of wounds sustained by U.S. soldiers in recent conflicts. The risk of infection is considerable with fracture fixation devices. In this pilot study, we examined the use of unique bactericidal micron-thin sol-gel films on fracture fixation devices and their ability to prevent and eradicate infections. External fixation was studied with micron-thin sol-gel coated percutaneous pins releasing triclosan and inserted medially into rabbit tibiae. A total of 11 rabbits received percutaneous pins that were either uncoated or sol-gel/triclosan coated. Internal fracture fixation was also studied using sol-gel coated intramedullary (IM) nails releasing vancomycin in the intramedullary tibiae. Six sheep received IM nails that were coated with a sol-gel film that either contained vancomycin or did not contain vancomycin. All animals were challenged with Staphylococcus aureus around the implant. Animals were euthanized at 1 month postoperative. Rabbits receiving triclosan/sol-gel coated percutaneous pins did not show signs of infection. Uncoated percutaneous pins had a significantly higher infection rate. In the sheep study, there were no radiographic signs of osteomyelitis with vancomycin/sol-gel coated IM nails, in contrast to the observations in the control cohort. Hence, the nanostructured sol-gel controlled release technology offers the promise of a reliable and continuous delivery system of bactericidals from orthopedic devices to prevent and treat infection. PMID:25102546

Qu, Haibo; Knabe, Christine; Burke, Megan; Radin, Shula; Garino, Jonathan; Schaer, Thomas; Ducheyne, Paul

2014-08-01

168

Single longitudinal mode lasing of coumarin-doped sol-gel silica laser  

Microsoft Academic Search

.   Homogeneity of sol-gel-derived silica was improved by slowing down the drying and aging rate. Single longitudinal mode lasing\\u000a was achieved in sol-gel silica doped with coumarin 460 dye. The laser linewidth was 1.58 GHz and the output wavelength was\\u000a at 467 nm.

S. K. Lam; X.-L. Zhu; D. Lo

1999-01-01

169

Single longitudinal mode lasing of coumarin-doped sol-gel silica laser  

Microsoft Academic Search

Homogeneity of sol-gel-derived silica was improved by slowing down the drying and aging rate. Single longitudinal mode lasing was achieved in sol-gel silica doped with coumarin 460 dye. The laser linewidth was 1.58 GHz and the output wavelength was at 467 nm.

S. K. Lam; X.-L. Zhu; D. Lo

1999-01-01

170

A comparative evaluation of corrosion protection of sol–gel based coatings systems  

Microsoft Academic Search

Sol–gel technology offers a wide choice of chemistries and is currently perceived as a potential replacement for current chromate treatments. The corrosion prevention behavior of a commercially available sol–gel surface pretreatment with six different primers was evaluated using electrochemical impedance spectroscopy. Eighteen different coatings systems were selected for evaluation. The test panels were prepared in three separate treatment groups of

M Khobaib; L. B Reynolds; M. S Donley

2001-01-01

171

Sol-Gel Processing of Amorphous Nanoporous Silicas: Thin Films and Bulk  

Microsoft Academic Search

The preceding discussion has illustrated that sol-gel processing is a versatile means of preparing ceramics with controlled nanostructures. Using simple strategies such as aggregation of fractals, controlled drying shrinkage, pyrolysis of organic templates, partial sintering and surface derivatization, pore sizes may be controlled in the nanometer and subnanometer ranges of interest for sensors, membranes, and catalysis. Compared to zeolites, sol-gel

C. Jeffrey Brinker; Stephen Wallace; Narayan K. Raman; Rakesh Sehgal; Joshua Samuel; Stephen Contakes

172

Thin film porous membranes based on sol-gel chemistry for catalytic sensors  

Microsoft Academic Search

Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel

R. C. Hughes; S. V. Patel; M. W. Jenkins; T. J. Boyle; T. J. Gardner; C. J. Brinker

1998-01-01

173

Fabrication of advanced electrochemical energy materials using sol-gel processing techniques  

NASA Technical Reports Server (NTRS)

Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

Chu, C. T.; Chu, Jay; Zheng, Haixing

1995-01-01

174

Investigations on the photocatalytic activity of sol–gel derived plain and Fe 3+\\/Nb 5+-doped titania coatings on glass substrates  

Microsoft Academic Search

Plain and doped (Fe3+ and Nb5+) titania coatings were deposited by dip coating on soda lime glass substrates using titania sol synthesized by sol–gel route in combination with commercial nanoparticle dispersions. The dopant concentrations were fixed at 0.07wt% and the coatings heat treated at 400°C were characterized with respect to their thickness, phase composition, hydrophilicity\\/hydrophobicity and microstructure. Photocatalytic activity testing

R. Subasri; M. Tripathi; K. Murugan; J. Revathi; G. V. N. Rao; T. N. Rao

2010-01-01

175

Epitaxial growth of La 2Zr 2O 7 thin films on rolled Ni-substrates by sol–gel process for high T c superconducting tapes  

Microsoft Academic Search

A solution process was used to grow epitaxial La2Zr2O7 (LZO) buffer layers on roll-textured Ni (100) substrates to produce YBa2Cu3O7?? (YBCO)-coated conductors. The LZO precursor solution was prepared by an all alkoxide sol–gel route using mixed metal methoxyethoxides in 2-methoxyethanol. The partially hydrolyzed solution was either spin-coated or dip-coated onto the textured Ni substrates. The amorphous thin film was then

T. G Chirayil; M. Paranthaman; D. B Beach; D. F Lee; A. Goyal; R. K Williams; X. Cui; D. M Kroeger; R. Feenstra; D. T Verebelyi; D. K Christen

2000-01-01

176

Alternative approaches to the fluorescence metrology of sol-gel nanoparticles using pH changes and thin films  

E-print Network

, University of Strathclyde, Glasgow, G4 0NG, Scotland, UK. Silica sol-gel related materials have widespread films the silica sol-gel behaves differently from in bulk solution, with the particles growing muchAlternative approaches to the fluorescence metrology of sol-gel nanoparticles using pH changes

Strathclyde, University of

177

Raman Studies of the Nanostructure of Sol-Gel Materials  

NASA Astrophysics Data System (ADS)

Four sol-gel systems (alumina, aluminum hydroxide, zirconia, and magnesia) were investigated, primarily by laser spectroscopy, on several series of materials prepared by systematically varying the synthesis procedures. Nanocrystalline boehmite, gamma -AlO(OH), was found to be the principal component in the sol-gel alumina system. Materials were prepared by the hot-water hydrolysis/condensation of rm Al(OC_4H_9)_3, the Yoldas process, as a function of process variables such as the time spent in the sol phase. Small but systematic changes, as a function of sol aging time, were discovered in the lineshape and position of the dominant boehmite Raman band observed in the alumina hydrogels. These spectral changes were interpreted in terms of nanocrystallinity-induced finite-size effects associated with the slow growth of AlO(OH) nanocrystals in the sol. X-ray diffraction experiments were used to determine nanocrystal sizes (as small as 3 nm for gels prepared from fresh sols) and to estimate growth kinetics from the Raman-lineshape results. These results appear to be among the first available for crystallite growth kinetics (ripening) in the near-atomic-scale nanocrystal regime. The trihydroxide polymorph system is closely related to the sol-gel alumina system. The processing temperature and the method of hydrolysis were varied, in order to determine their effect on the trihydroxide phase mix. The trihydroxide phase mix does not change with time; it depends only on the initial hydrolysis conditions. Bayerite is the primary phase present for materials processed at 25 C, while nordstrandite is the primary phase present for materials processed at 60 C. It is shown that the trihydroxide crystal nucleation kinetics are responsible for the Al(OH)_3 phase mix. Hydroxide/oxyhydroxide phase-mix kinetics were also studied; this ratio increases with time. The associated rate constant decreases with increasing temperature. Sol-gel zirconia was prepared by using atmospheric water to hydrolyze a mixture of zirconium propoxide, acetic acid, and n-propanol. This produces a clear gel. Hydrogen peroxide was found to chemically react with the gels. Clean Raman spectra reveal a broad-band structure (the full width at half maximum is 150 cm^{-1} ) centered at about 460 cm^{ -1}. Raman and luminescent spectra (both obtained on the Raman spectrometer) were used to monitor the conversion of magnesium-carbonate-based materials to magnesium oxide, as a function of temperature. This new phase-determination technique utilizes the krypton 674.1 nm laser line so that the carbonate symmetric-stretch band and the MgO:Cr ^{+++} luminescence band are readily observable on the same spectrum. (Abstract shortened by UMI.).

Doss, Calvin James

178

Sol-gel multilayers applied by a meniscus coating process  

SciTech Connect

We describe a meniscus coating method to produce high-laser damage threshold, silica/alumina sol-gel multilayer reflectors on 30 {plus} cm substrates for laser-fusion applications. This process involves forcing a small suspension flow through a porous applicator tube, forming a falling film on the tube. A substrate contacts this film to form a meniscus. Motion of the substrate relative to the applicator entrains a thin film on the substrate, which leaves behind a porous, optical quality film upon solvent evaporation. We develop a solution for the entrained film thickness as a function of geometry, flow and fluid properties by an analysis similar to that of the classical dip-coating problem. This solution is compared with experimental measurements. Also, preliminary results of multilayer coating experiments with a prototype coater are presented, which focus on coating uniformity and laser damage threshold (LDT).

Britten, J.A.; Thomas, I.M.

1992-03-19

179

Microstructural evolution of titania sol-gel thin films  

SciTech Connect

Thin films of crystalline titania with different grain sizes and porosities were prepared by dip-coating on Si (100) substrates starting from a sol-gel process. Three synthesis procedures were developed and compared, using acetylacetone (acac, with HCl) and acetic acid (HOAc) as modifying agents or directly using hydrochloric acid as catalyst. The structural evolution of the films was characterized by Glazing Angle X-ray Diffraction (XRD), Spectroscopic Ellipsometry and Atomic Force Microscopy (AFM). Anatase phase was observed on all of the films calcined at 440 C. The grain sizes and crystallinity generally increased with calcination temperature. Thin films obtained from acac and HOAc-modified titanium sols had fine grains (50--80 nm) and less porosity (<10%) after calcination at 1,000 C. Thin films derived from the sol catalyzed directly with acid had the largest grains (90--130 nm), higher crystallinity and greater porosity (17%).

Yan, Y.; Chaudhuri, S.R.; Chen, D.G.; Bolker, B.; Sarkar, A. [YTC America Inc., Camarillo, CA (United States)

1994-12-31

180

Magnetic thin films produced by sol-gel processes  

NASA Astrophysics Data System (ADS)

Iron oxide films on borosilicate glasses were produced with the sol-gel method. The ESR spectra of the as-produced films exhibit two signals, one at g about 4.2 and the other at g about 2. A ferromagnetic signal was detected by heat-treating the samples in hydrogen atmosphere between 500 and 800 °C. Angular variation of the ferromagnetic resonance signals revealed an internal field parallel to the plane of the films. The internal field was about 3500 G in the film heat treated at 620 °C for 120 min. Scanning electron microscopy was also used for detailed surface characterization. Before treatments the film is characterized by a fine texture and a few voids whose dimensions are about 5×15 ?. After treatments the film contains particles about 15 ? in size.

Kordas, G.; Weeks, R. A.; Arfsten, N.

1985-04-01

181

Photosensitivity in a silica-based sol-gel glass  

SciTech Connect

Photosensitivity in glasses containing Au and Ce was first reported by Dalton in 1943 and later reaffirmed by Stookey. The photothermal reduction of Au ions to form metallic colloids was determined to be responsible for the {open_quotes}ruby{close_quotes} color produced in these glasses. In this work, the photosensitive effect has been confirmed for the first time in a silica sol-gel glass containing Au and Ce. Two methods of producing Au colloids in this glass were investigated, one involved a short ultraviolet (UV) exposure followed by a thermal treatment, the other a simultaneous UV irradiation and thermal treatment. Colloid formation was studied using optical absorption spectroscopy, whereas the role of Ce in the photosensitive process was elucidated using optical absorption and fluorescence spectroscopic techniques.

Korwin, D.M.; Pye, L.D. [Alfred Univ., NY (United States)

1996-12-31

182

Active sol-gel thin film on nanostructured plasmonic surface  

NASA Astrophysics Data System (ADS)

Sol-gel hybrid films based on alkyl bridged polysilsesquioxanes and doped with phenol red molecules, were synthesized for sensing purposes. Doped films changes colour from yellow to orange to red when exposed to hydrochloric acid (HCl) both in solution and gas phases. The synthesis was optimized in order to produce porous films after spin coating. The porosity increases reacting surface area and chemical reactivity of the sensing thin film. Porosity, optical and structural characterizations of these films were investigated by transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Spectroscopic Ellipsometry (SE). Variation of optical characteristics upon immersion of the film in the solution was characterized by UV-visible (UV-vis) spectroscopy. Moreover the same porous sensitive hybrid film was deposited on gold sinusoidal grating in order to detect variations of the dielectric film optical constant after HCl solution dip. This variation was revealed by monitoring surface plasmon polariton excitations.

Pistore, A.; Guglielmi, M.; Brusatin, G.; Kang, H. K.; Ferraris, C.; Romanato, F.

2010-11-01

183

Entropic Elasticity at the Sol-Gel Transition  

E-print Network

The sol-gel transition is studied in two purely entropic models consisting of hard spheres in continuous three-dimensional space, with a fraction $p$ of nearest neighbor spheres tethered by inextensible bonds. When all the tethers are present ($p=1$) the two systems have connectivities of simple cubic and face-centered cubic lattices. For all $p$ above the percolation threshold $p_c$, the elasticity has a cubic symmetry characterized by two distinct shear moduli. When $p$ approaches $p_c$, both shear moduli decay as $(p-p_c)^f$, where $f\\simeq 2$ for each type of the connectivity. This result is similar to the behavior of the conductivity in random resistor networks, and is consistent with many experimental studies of gel elasticity. The difference between the shear moduli that measures the deviation from isotropy decays as $(p-p_c)^h$, with $h\\simeq 4$.

Oded Farago; Yacov Kantor

2001-05-24

184

Ceramic superconductors synthesized by sol-gel methods  

NASA Astrophysics Data System (ADS)

A sol-gel method is described based on the use of organic complexing agents in liquid solution, such as citric acid, ethylene-diamine-tetra-acetic acid (EDTA) and others. It is shown how the procedures can be designed on a scientific basis, using pM?-pH diagrams for the respective cation and complexing agent. This technique yields powders and sintered materials with superior properties to the dry mix and calcine method. An important advantage of the method is its versatility due to the fact that stable complexes can be formed for a wide range of elements. Precise control of stoichiometry is possible, however the residual carbon level is more difficult to control.

Van der Biest, O.; Kwarciak, J.; Dierickx, D.; Dhalle, M.; Boon, W.; Bruynseraede, Y.

185

Mayenite Synthesized Using the Citrate Sol-Gel Method  

SciTech Connect

A citrate sol-gel method has been used to synthesize mayenite (Ca12Al14O33). X-ray powder diffraction data show that the samples synthesized using the citrate sol-gel method contained CaAl2O4 and CaCO3 along with mayenite when fired ex-situ in air at 800 C but were single phase when fired at 900 C and above. Using high temperature x-ray diffraction, data collected in-situ in air at temperatures of 600 C and below showed only amorphous content; however, data collected at higher temperatures indicated the first phase to crystallize is CaCO3. High temperature x-ray diffraction data collected in 4% H2/96% N2 does not show the presence of CaCO3, and Ca12Al14O33 starts to form around 850 C. In comparison, x-ray powder diffraction data collected ex-situ on samples synthesized using traditional solid-state synthesis shows that single phase was not reached until samples were fired at 1350 C. DTA/TGA data collected either in a nitrogen environment or air on samples synthesized using the citrate gel method suggest the complete decomposition of metastable phases and the formation of mayenite at 900 C, although the phase evolution is very different depending on the environment. Brunauer-Emmett-Teller (BET) measurements showed a slightly higher surface area of 7.4 0.1 m2/g in the citrate gel synthesized samples compared to solid-state synthesized sample with a surface area of 1.61 0.02 m2/g. SEM images show a larger particle size for samples synthesized using the solid-state method compared to those synthesized using the citrate gel method.

Ude, Sabina N [ORNL] [ORNL; Rawn, Claudia J [ORNL] [ORNL; Meisner, Roberta A [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL)] [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Kirkham, Melanie J [ORNL] [ORNL; Jones, Gregory L. [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Payzant, E Andrew [ORNL] [ORNL

2014-01-01

186

Synthesis and characterization of nitric oxide-releasing sol-gel microarrays.  

PubMed

Diazeniumdiolate-modified sol-gel microarrays capable of releasing low levels of nitric oxide are reported as a viable means for improving the blood compatibility of a surface without fully modifying the underlying substrate. Several parameters are characterized including: (1) NO surface flux as a function of sol-gel composition and microarray geometry; (2) microstructure dimensions and spacing for optimal blood compatibility; and (3) the effect of sol-gel surface modification on analyte accessibility to platinum electrodes. The sol-gel microarrays release biologically relevant levels of NO under physiological conditions for >24 h. In vitro platelet adhesion assays indicate that a NO surface flux of 2.2 pmol cm(-2) s(-1) effectively reduces platelet adhesion to glass substrates modified with sol-gel microstructures separated by 50 microm. The blood compatibility observed for these micropatterned surfaces is comparable to NO-releasing sol-gel films. When the separation between NO-releasing microstructures is reduced to 10 microm, the NO surface flux required to reduce platelet adhesion is lowered to 0.4 pmol cm(-2) s(-1). Finally, the oxygen response of platinum electrodes modified with NO-releasing sol-gel microarrays indicates that selective modification via micropatterning enhances analyte accessibility to the sensor surface. PMID:15518528

Robbins, Mary E; Hopper, Erin D; Schoenfisch, Mark H

2004-11-01

187

Sol-gel processes and materials. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search  

SciTech Connect

The bibliography contains citations of selected patents concerning sol-gel processes and sol-gel derived materials and products. Selected patents include sol-gel compositions, ceramic and refractory materials, fabrication of silica glass, sol-gel thin films and coatings, transparent inorganic oxide glass, luminescent quartz glass, catalysts and catalyst supports, nuclear fuels preparation, abrasives for grinding wheels, sol-gel production of microspheres, alumina composites, photographic materials, and dental materials. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1995-12-01

188

Mediated patterning of sol-gel thin layers: Shrinkage, decohesion, and lift-off  

NASA Astrophysics Data System (ADS)

This thesis explores the unique de-cohesion and lift-off processes that occur during mediated patterning of integrated sol-gel thin films of functional materials. Mediated deposition, an additive patterning approach, was introduced by Jeon et al. (J. Mater. Res., 10[12]: 2996--9 (1995)), where microcontact printing (mu-CP) facilitated the selective transfer of a molecular 'ink' (e.g., octadecyltrichlorosilane, ODTS) to the substrate, and de-cohesion of sol-gel films occurred exclusively above the printed ink regions after heat treatment (<150°C). Patterned sol-gel films of uniform thickness were revealed after facile lift-off of cracked fragments, without the use of etchants. In this thesis, the origin and mechanics of de-cohesion and lift-off were determined through direct observations and measurements. The disparate mechanical behaviors of sol-gel films on functionalized and unmodified surfaces were determined, with emphasis on interfacial strength, in-plane biaxial stress, thin film mechanics, and crack propagation for sol-gel layers on silicon, glass and fused silica substrates. In addition, direct patterning of sol-gel layers was demonstrated for the first time on curved glassy surfaces using mu-CP and mediated patterning methods. The shrinkage and densification of sol-gel layers were determined by in-situ and ex-situ measurements, where a ˜30% decrease in thickness (t) was typical during drying of sol-gel layers (T < 300°C). Constrained shrinkage, resulting from adhesion to the supporting silicon substrate, led to a coherent (crack-free) film with biaxial stresses of ˜200 MPa (t ˜ 50 nm). For ODTS-mediated sol-gel films, however, precise in-situ wafer curvature measurements determined that film stresses never exceeded 75 MPa. Additionally, interfacial adhesive strength between the substrate and the sol-gel film were evaluated for the first time using a unique pulsed-laser stress-wave technique. An adhesive strength threshold of 15 MPa was determined for sol-gel films on ODTS-functionalized silicon, whereas, the threshold strength of films deposited on unmodified silicon was determined as >25 MPa and greater than the fracture strength of silicon. In this work, hydrophobic surface regions, facilitated by directed mu-CP of a molecular film, affected adhesion so as to reduce the substrate constraint and promote de-cohesion of the sol-gel film on the sub-micron scale. That is, selective de-cohesion and lift-off were enabled by the control of local mechanical interfacial constraints.

Mikalsen, Erik Arthur

189

Vapor-Diffusion-Controlled Sol-Gel Synthesis of Flaky Lithium Vanadium Oxide and Its Electrochemical Behavior  

SciTech Connect

Effectively modifying an existing synthesis method for materials can prove as useful as developing a new one. In this work, we revisited a conventional sol?gel synthesis of lithium vanadium oxide, a promising electrode material for rechargeable lithium batteries. Employing a kinetically controlled, vapor diffusion strategy (in which ammonia vapor was slowly diffused into the solution), we modified the conventional method to obtain a thin, flaky, lithium vanadium oxide with an average thickness of ?120 nm. In comparison, material prepared by the conventional sol?gel route (in which aqueous ammonia was dropwise added to the solution) exhibited an agglomeration of irregular particles with a typical size of ?10 ?m. When evaluated as cathode material for rechargeable lithium batteries, this flaky material displayed a stable, reversible capacity of ?250 and ?115 mAh/g at discharge rates of 0.1 C and 2 C, respectively, considerably better than the agglomerated sample. The reasons for this improved performance were investigated by evaluating the electrochemical reaction kinetics, morphological and structural stability using cyclic voltammetry, scanning electron microscopy, and X-ray diffraction.

Zhang, Hong-Li; Neilson, James R.; Morse, Daniel E.

2010-01-01

190

Laser micromachining of hybrid sol-gels: application to fabrication of micro-optical elements  

NASA Astrophysics Data System (ADS)

We have prepared an organic/inorganic hybrid using sol-gel process. The material exhibits thermal, mechanical and optical properties well adapted to the patterning by laser micromachining. We have achieved the fabrication of optical elements by this mean validating the process at micrometric scale. Optical waveguides have been fabricated in 3-4 micrometer thick hybrid sol-gel films deposited by spin coating on borosilicate glass substrates. Here laser ablation is used to remove matter on both sides of the waveguide core. The laser micromachining of hybrid sol-gel is also adapted to the fabrication of multilevel diffractive optical elements. Indeed, the ablation depth can be precisely controlled by the fluence of the laser and/or the number of pulses. This study demonstrates that laser micromachining of hybrid sol-gels permits the fast fabrication of effective optical devices, making this process well adapted to rapid prototyping or fabrication of masters.

Clauss, Estelle; Rehspringer, Jean-Luc; Mager, Loïc; Fort, Alain; Fontaine, Joël

2006-04-01

191

The physics and chemistry of semiconductor nanocrystals in sol-gel derived optical microcavities  

E-print Network

The incorporation of semiconductor nanocrystals (NCs) into sol-gel derived matrices presents both novel applications as well as a robust platform in which to investigate the nonlinear optical properties of NCs. This thesis ...

Chan, Yinthai

2006-01-01

192

High second-order optical nonlinearities in thermally poled sol-gel silica  

NASA Astrophysics Data System (ADS)

Silica glass samples prepared by a sol-gel process, the mixture of silica sol for gelation and colloidal silica particles, have been thermally poled in vacuum by continuous high voltage (8-12 kV) at elevated temperature (280 °C). High second-order nonlinearities (>1 pm/V), located under the anodic surface, have been measured and the values are higher than those obtained in fused silica glass, poled under the same conditions. A model for thermal poling is suggested which explains the experimental results in sol-gel silica and the difference between thermal poling of sol-gel and fused silica. The granular structure and the boundaries of sol-gel silica seem to play a major role in establishing the electrical properties of the depletion layer during and after poling.

Pruneri, V.; Bonfrate, G.; Kazansky, P. G.; Takebe, H.; Morinaga, K.; Kohno, M.; Kuwasaki, K.; Takeuchi, T.

1999-05-01

193

Production of cerium oxide microsheres by an internal gelation sol-gel process  

E-print Network

The experiments performed for this research were completed to produce solid cerium oxide microspheres by an internal gelation sol-gel process. The motivation for this work was to develop a process that would enable the fabrication of a storage...

Wegener, Jeffrey J.

2010-01-14

194

Molecular receptors in metal oxide sol-gel materials prepared via molecular imprinting  

DOEpatents

A method is provided for molecularly imprinting the surface of a sol-gel material, by forming a solution comprised of a sol-gel material, a solvent, an imprinting molecule, and a functionalizing siloxane monomer of the form Si(OR).sub.3-n X.sub.n, wherein n is an integer between zero and three and X is a functional group capable of reacting with the imprinting molecule, evaporating the solvent, and removing the imprinting molecule to form the molecularly imprinted metal oxide sol-gel material. The use of metal oxide sol-gels allows the material porosity, pore size, density, surface area, hardness, electrostatic charge, polarity, optical density, and surface hydrophobicity to be tailored and be employed as sensors and in catalytic and separations operations.

Sasaki, Darryl Y. (Albuquerque, NM); Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Daitch, Charles E. (Charlottesville, VA); Shea, Kenneth J. (Irvine, CA); Rush, Daniel J. (Philadelphia, PA)

2000-01-01

195

Sol–gel horseradish peroxidase biosensor for hydrogen peroxide detection by chemiluminescence  

Microsoft Academic Search

Horseradish peroxidase (HRP) was immobilized by microencapsulation in sol–gel crystals derived from tetramethyl orthosilicate. A sol–gel biosensor based on the chemiluminescence reaction of the hydrogen peroxide–luminol–HRP system was developed. Calibration plots for hydrogen peroxide have been established by chemiluminescence measurements in a cuvette and through an optical fibre modified at its end with the immobilized HRP gel. The detection limit

A Navas D??az; M. C Ramos Peinado; M. C Torijas Minguez

1998-01-01

196

Bioencapsulation within synthetic polymers (Part 1): sol–gel encapsulated biologicals  

Microsoft Academic Search

Since its inception a decade ago, sol–gel encapsulation has opened up an intriguing new way to immobilize biological materials. An array of substances, including catalytic antibodies, DNA, RNA, antigens, live bacterial, fungal, plant and animal cells, and whole protozoa, have been encapsulated in silica, metal-oxide, organosiloxane and hybrid sol–gel polymers. The advantages of these ‘living ceramics’ might give them applications

Iqbal Gill; Antonio Ballesteros

2000-01-01

197

Bioencapsulation within synthetic polymers (Part 2): non-sol–gel protein–polymer biocomposites  

Microsoft Academic Search

Since the introduction of sol–gel bioencapsulation and the demonstration that biological function can be incorporated into, and preserved within, polymer matrices, a number of alternative polymers have been used to immobilize proteins. Various enzymes have been trapped in such diverse polymers as epoxy-amine resins, polyvinyl plastics, polyurethane foams and silicone elastomers. Together with sol–gel encapsulates, these biocomposites represent a powerful

Iqbal Gill; Antonio Ballesteros

2000-01-01

198

Microstructure Control of RF and Carbon Aerogels Prepared by Sol-Gel Process  

Microsoft Academic Search

Carbon aerogels derived from an organic sol-gel process and supercritical drying are novel porous materials with interconnected structures and high electrical conductivity, which are considered to be ideal electrode materials for supercapacitors and rechargeable batteries. In this paper we report resorcinol-formaldehyde (RF) aerogels that have been prepared with high RC ratio (molar ratio of resorcinol to catalyst) by sol-gel process

Jun Shen; Jinqiang Hou; Yanzhi Guo; Hui Xue; Guangming Wu; Bin Zhou

2005-01-01

199

Influence of the Layer Morphology on the Electrical Properties of Sol Gel Transparent Conducting Oxide Coatings  

Microsoft Academic Search

Tranparent conducting coatings have been prepared by sol gel methods either by a conventional sol-gel process (Antimony doped Tin Oxide—ATO, Aluminium doped Zinc Oxide—AZO) or a new wet chemical process using fully dispersed crystalline nanoparticles (ATO, Indium Tin Oxide—ITO). The dip coating technique has been used as deposition technique with single coating thickness varying from a few nanometer to ca.

Christian Goebbert; Guido Gasparro; Thomas Schuler; Thomas Krajewski; Michel A. Aegerter

2000-01-01

200

Preparation of C[sub 70]-doped solid silica gel via sol-gel process  

Microsoft Academic Search

In this paper, the authors report a successful fabrication of C[sub 70]-doped silica solid gel via the sol-gel technique. The sol-gel process is a technique that can be used to prepare transparent oxide glasses by hydrolysis and condensation of alkoxide precursors. Little or no heating is required, and consequently the gel can be doped with molecules whose poor thermal stability

S. Dai; J. P. Young; R. N. Compton; G. Mamantov

1992-01-01

201

Composition-dependent performance of sol–gel host matrices doped with Rh 6G  

Microsoft Academic Search

Laser dye rhodamine 6G (Rh 6G) was incorporated into sol–gel glasses prepared by using three methods: (i) by using HCl as catalyst, (ii) by using HNO3 as catalyst and (iii) by using HNO3 as catalyst and formamide as drying control chemical additive (DCCA). The performance of these sol–gel matrices as hosts was evaluated by studying the absorption\\/fluorescence behavior of the

Aparna V Deshpande; Rashmi R Panhalkar

2002-01-01

202

Synthesis and characterization of sol gel silica films doped with size-selected gold nanoparticles  

Microsoft Academic Search

Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol-gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous\\/organic system and, subsequently, dispersed in an acid-catalysed sol-gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction

M. C. Ferrara; L. Mirenghi; A. Mevoli; L. Tapfer

2008-01-01

203

Electrosynthesis of thin sol–gel films at a three-phase junction  

Microsoft Academic Search

Thin, functionalised silica films of between 4 and 15nm thickness were prepared by sol–gel processing at an electrode organic phase aqueous phase junction by slow withdrawal of a conducting support through the liquid–liquid interface. Protons were electrogenerated in the aqueous phase and catalysed the hydrolysis of the sol–gel precursor in the organic phase. The film was characterised using atomic force

Joanna Niedziolka-Jonsson; Martin Jonsson-Niedziolka; Wojciech Nogala; Barbara Palys

2011-01-01

204

A novel impedimetric immunosensor based on sol-gel derived Barium Strontium Titanate composite filnm  

Microsoft Academic Search

We report the development of a novel impedimetric immunosensor based on sol-gel derived barium strontium titanate (BST) composite film. On a platinum electrode, a layer of rough and porous BST composite film is deposited using sol-gel technique. A gold electrode is placed in parallel to the Pt electrode with a separating distance of 1 mm. 10 muL Dl water is

Sun Lingling; Tan Ooi Kiang; Mao Baowei; Tan Lay Im; Gan Leong Huat; Gan Yik Yuen

2006-01-01

205

Oxidation protection of carbon-carbon composites by sol-gel ceramic coatings  

Microsoft Academic Search

Carbon-carbon composites were coated with Calcium Magnesium Zirconium Phosphate (CMZP) and Mg-doped Al2TiO5 sol-gels in order to form an oxygen barrier at temperatures above ~650°C. The coatings were applied using a dipping technique and controlled drying procedures. It was determined that 10 coats of CMZP sol-gel fired every other coat created crack free coatings and oxidation protection. Mg-doped AlTi2O5 coatings

J. N. Stuecker; D. A. Hirschfeld; D. S. Martin

1999-01-01

206

Characterization of LiTaO3 thin films fabricated by sol-gel technique  

Microsoft Academic Search

Lithium tantalite (LiTaO3) thin films have been fabricated by sol–gel technique and crystallized by RTA process. The effect of heating temperature on the structural properties of LiTaO3 is investigated. The thin films are characterized by means of X-ray diffraction, Raman spectroscopy and thermal analysis (DCA\\/DTA). After the optimization of the growth parameters of LiTaO3 prepared by sol–gel processing, the pyroelectric

S. Youssef; R. Al Asmar; J. Podlecki; F. Pascal-delannoy; Y. Zaatar; A. Foucaran

2007-01-01

207

Piezoelectric thick film ultrasonic transducers fabricated by a sol–gel spray technique  

Microsoft Academic Search

Thick film broadband ultrasonic transducers (UTs) produced by a sol–gel spray technique and operated below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol–gel solution. The 50–100 ?m thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a

M Kobayashi; T. R Olding; M Sayer; C.-K Jen

2002-01-01

208

Scale effects in abrasive wear of composite sol–gel alumina coated light alloys  

Microsoft Academic Search

Chemically-bonded composite sol–gel (CB-CSG) coatings have been developed that incorporate calcined ceramic powder particles (filler) dispersed in a sol–gel (SG) matrix (binder). As a result, they have significantly reduced densification strains compared to conventional SG coatings. The CB-CSG coatings, which are several orders of magnitude thicker than typical micron-thick SG films, can be produced easily by spray depositing onto Al

S Wilson; H. M Hawthorne; Q Yang; T Troczynski

2001-01-01

209

Evaluation and characterization of nanostructure hydroxyapatite powder prepared by simple sol–gel method  

Microsoft Academic Search

Many attempts have been focused on preparing of synthetic hydroxyapatite (HA), which closely resembles bone apatite and exhibits excellent osteoconductivity. Low temperature formation and fusion of the apatite crystals have been the main contributions of the sol–gel process in comparison with conventional methods for HA powder synthesis. This paper describes the synthesis of nano-HA particles via a sol–gel method. Nanocrystalline

M. H. Fathi; A. Hanifi

2007-01-01

210

Spectroscopic properties of cerium in sol-gel glasses  

NASA Astrophysics Data System (ADS)

Glasses containing Ce were prepared by the sol-gel method at elevated temperatures. Two parallel series, one in air and one in nitrogen atmosphere, were obtained. The main constituent of the glasses was silica SiO 2 obtained by hydrolysis of ethoxysilane (TEOS). Spectroscopic properties of the glasses were studied by time-resolved and steady-state luminescence spectroscopy. In the present paper we made an effort to distinguish between the blue luminescence arising from Ce(III) and that obtained from the silica host which is connected with defects in the matrix. While the spectra of both pure silica and Ce activated silica excited at 337 nm or longer wavelength have the similar emission peaking between 400 and 450 nm, the emission of silica is broader and its decay time shorter than that of Ce(III). It seems that Ce quenches the luminescence of the silica centers. When excited at 308 nm by an excimer laser we detect short-lived emission of Ce(III) peaking between 350-380 nm which may be due to excitation to the conductivity band and subsequent recombination of the excited electrons with a hole.

Reisfeld, Renata; Patra, Amitava; Panczer, Gerard; Gaft, Michael

1999-10-01

211

Transparent conductive sol-gel thin films for photonic applications  

NASA Astrophysics Data System (ADS)

Antimony doped tin dioxide (SnO2:Sb) thin films are fabricated by a new simplified sol-gel process. Films are prepared from an alcoholic solution of SnCl4(DOT)4H2O doped with SbCl3. Films are deposited by the spin coating process on sodalime glass, borosilicate glass, silicon wafers and ceramic alumina substrates. The chemical reactions during the heat treatment are monitored by DSC and TG. The chemical composition of the coatings are determined by scanning electron microscopy (SEM). Sheet resistance, Rs, is measured using a linear four-probe technique. Optical properties of the films are also determined. The resistivity of the thin films are presented as a function of the antimony doping level. The smallest sheet resistance of 200 (Omega) /$DAL is found for a 250 nm thick coating on a borosilicate substrate. It is observed that the sheet resistance does not decrease linearly with increasing film thickness. Fabrication possibilities of these materials for the integrated optics based sensors including patterning methods are discussed.

Kololuoma, Terho K.; Rantala, Juha T.; Vaehaekangas, Jouko; Laitinen, Risto S.

1999-03-01

212

Control of rehydration in sol-gel glasses  

NASA Astrophysics Data System (ADS)

Optical properties of monoliths synthesized via the sol gel process result in a large number of residual silanol (Si-OH) groups, even after annealing at 900 C. High silanol content quenches emission from rare earth ions via excitation of vibrations of the silanol groups. Medium density glasses (1.5gcm-3) have a highly interconnected porous structure that allows the diffusion of molecules throughout the material. Diffusion of atmospheric water molecules results in chemiadsorption reactions that increase silanol group content, adding to quenching. By monitoring the intensity of terbium (Tb^3+) emissions from the ^5D3 level relative to the ^5D4 level, we report an 80% decrease in ratio within 12 hours. Monoliths prepared with of N,N-dimethylformamide, a drying control chemical additive (DCCA), were annealed at 1050 C and maintained good optical quality with nearly complete densification of the material (2.1gcm-3). DCCAs minimize the capillary stresses in the network during drying, even during the onset of viscous flow at the glass transition. Monoliths prepared with DMF and annealed at 1050 C for 6 hours showed no change in their ^5D3: ^5D4 intensity ratio upon exposure to the atmosphere.

Ortiz, Carlos; Boye, Daniel

2007-11-01

213

Sol-gel template synthesis of semiconductor nanostructures  

SciTech Connect

The template method for preparing nanostructures entails synthesis of the desired material within the pores of a nanoporous membrane or other solid. A nonofibril or tubule of the desired material is obtained within each pore. Methods used previously to deposit materials within the pores of such membranes include electrochemical and electroless deposition and in situ polymerization. This paper describes the first use of sol-gel chemistry to prepare semiconductor nanofibrils and tubules within the pores of an alumina template membrane. TiO{sub 2}, WO{sub 3}, and ZnO nanostructures have been prepared. TiO{sub 2} nanofibrils with diameters of 22 nm were found to be single crystals of anatase with the c-axis oriented along the fibril axis. Bundles of these fibrils were also found to be single crystalline, suggesting that the individual fibrils are arranged in a highly organized fashion within the bundle. Finally, 200 nm diameter TiO{sub 2} fibrils were used as photocatalysts for the decomposition of salicylic acid. 30 refs., 8 figs.

Lakshmi, B.B.; Dorhout, P.K.; Martin, C.R. [Colorado State Univ., Fort Collins, CO (United States)] [Colorado State Univ., Fort Collins, CO (United States)

1997-03-01

214

/dopamine films prepared by sol-gel method  

NASA Astrophysics Data System (ADS)

Dopamine was encapsulated into nanoporous amorphous TiO2 matrix by sol-gel method under atmospheric conditions. A second sample was obtained by the addition of the crown-ether 15C5 in this previous sample. Thin films were spin-coated on glass wafers. No heat treatment was employed in both films. All films were characterized using infrared spectroscopy, high resolution transmission electronic microscopy, X-ray diffraction, optical absorption and scanning electronic microscopy. Despite the films prepared with 15C5 were no calcined, a partial crystallization was identified. Anatase and rutile nanoparticles with sizes of 4-5 nm were obtained. Photoconductivity technique was used to determine the charge transport mechanism on these films. Experimental data were fitted with straight lines at darkness and under illumination wavelengths at 320, 400, and 515 nm. It indicates an ohmic behavior. Photovoltaic and photoconductivity parameters were determined from the current density vs. the applied-electrical-field results. Amorphous film has bigger photovoltaic and photoconductive parameters than the partially crystalline film. Results observed in the present investigation prove that the nanoporous TiO2 matrix can protect the dopamine inhibiting its chemical instability. This fact modifies the optical, physical and electrical properties of the film, and is intensified when 15C5 is added.

Valverde-Aguilar, G.; Prado-Prone, G.; Vergara-Aragón, P.; Garcia-Macedo, J.; Santiago, Patricia; Rendón, Luis

2014-09-01

215

Development and application of sol-gel-derived platforms for chemical and biological sensing  

NASA Astrophysics Data System (ADS)

The sol-gel process allows the production of controlled pore glasses under ambient temperature and pressure conditions. The low temperature processing conditions allows the incorporation of organic and even biological species within these glass composites. Thus, the tunable physical characteristics of the final sol-gel composite (e.g., porosity, refractive index) coupled with the ability to "immobilize" chemical and biological recognition elements within these matrices, make them attractive as chemical sensing platforms. The successful inclusion of a recognition element within these matrices requires a detailed understanding of how the sol-gel-processed materials affects the dopant species. Toward this end, we have investigated the behavior of a series of model dopants (organic fluorophores and proteins) entrapped within sol-gel-derived composites as a means to determine the sol-gel-processed composite affects the dopant. We also present new methods for producing stable, sol-gel-based thin films. Finally, we used these thin-film formats to produce a prototypical immunosensor, and tunable pressure-sensitive coatings.

Jordan, Jeffrey David

216

Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction  

SciTech Connect

Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of Diels-Alder adduct used as the bridging group, we can change the temperature at which the retro-Diels-Alder reaction will occur.

SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.; PRABAKAR,SHESHASAYANA; GREAVES,JOHN; SHEA,KENNETH J.

1999-12-08

217

Fabrication of highly uniform and porous MgF2 anti-reflective coatings by polymer-based sol-gel processing on large-area glass substrates  

NASA Astrophysics Data System (ADS)

Despite recent progress in the fabrication of magnesium fluoride (MgF2) anti-reflective coatings (ARCs), simple, effective and scalable sol-gel fabrication of MgF2 ARCs for large-area glass substrates has prospective application in various optoelectronic devices. In this paper, a polymer-based sol-gel route was devised to fabricate highly uniform and porous MgF2 ARCs on large-area glass substrates. A sol-gel precursor made of polyvinyl acetate and magnesium trifluoroacetate assisted in the formation of uniformly mesoporous MgF2 ARCs on glass substrates, leading to the attainment of a refractive index of ˜1.23. Systematic optimization of the thickness of the ARC in the sub-wavelength regime led to achieving ˜99.4% transmittance in the case of the porous MgF2 ARC glass. Precise control of the thickness of porous MgF2 ARC glass also resulted in a mere ˜0.1% reflection, virtually eliminating reflection off the glass surface at the target wavelength. Further manipulation of the thickness of the ARC on either side of the glass substrate led to the fabrication of relatively broadband, porous MgF2 ARC glass.

Raut, Hemant Kumar; Safari Dinachali, Saman; Konadu Ansah-Antwi, Kwadwo; Anand Ganesh, V.; Ramakrishna, Seeram

2013-12-01

218

Large-area sol-gel highly-reflective coatings processed by the dipping technique  

SciTech Connect

The Centre d`Etudes de Limeil-Valenton is currently involved in a project which consists of the construction of a 2 MJ/500TW (351-nm) pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research. With 240 laser beams, the proposed megajoule-class laser conceptual design necessitates 44-cm x 2 44-cm x 6-cm cavity-end mirrors (1053-nm) representing more than 50-m{sup 2} of coated area. These dielectric mirrors are made of quaterwave stacks of SiO{sub 2} and ZrO{sub 2}-PVP (PolyVinylPyrrolidone) and are prepared from colloidal suspensions (sols) using the sol-gel route. After a sustained search effort. we have prepared (SiO{sub 2}/ZrO{sub 2}-PVP){sup 10} mirrored coatings with up to 99% reflection at 1053-nm and for different incidence use. Adequate laser-conditioned damage thresholds ranging 14 - 15 J/cm{sup 2} at 1053-nm wavelength and with 3-ns pulse duration were achieved. Large-area mirrors with good coating uniformity and weak edge-effect were produced by dip-coating at room temperature and atmospheric pressure.

Belleville, P. [CEA - Centre d`Etudes de Limeil-Valenton, Saint George (France); Pegon, P. [REOSC - Groupe Sfim, St Pierre du Perray (France)

1997-12-01

219

Glass-based confined structures fabricated by sol-gel and radio frequency sputtering  

NASA Astrophysics Data System (ADS)

Some of the main results obtained in the field of glass-based photonic crystal (PC) systems using complementary techniques, such as radio frequency (RF) sputtering and sol-gel route, are presented. Initially, rare earth-activated one-dimensional PCs fabricated by RF-sputtering technique will be discussed, specifically the cavity is constituted by an Er-doped SiO active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO2/TiO2 layers. Moreover, from near infrared, transmittance and variable angle reflectance spectra have verified the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm at 0 deg and quality factor of 890. In the second case, a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix will be presented in detail. This system has been designed as a structure that displays an iridescent green color that can be attributed to the PC effect. This feature has been exploited to create a chemical sensor; in fact optical measurements have evidenced that this system presents a different optical response as a function of the solvent applied on the surface, showing: (1) high sensitivity, (2) fast response, and (3) reversibility of the signal change.

Chiappini, Andrea; Armellini, Cristina; Carpentiero, Alessandro; Vasilchenko, Iustyna; Lukowiak, Anna; Risti?, Davor; Varas, Stefano; Normani, Simone; Mazzola, Maurizio; Chiasera, Alessandro

2014-07-01

220

Optical constants and electrochromic properties of sol-gel V{2}O{5} thin films  

NASA Astrophysics Data System (ADS)

Vanadium pentoxide thin films are prepared by the sol-gel route by dissolving V{2}O{5} powder (99.5% purity) in H{2}O{2} solution. The solution is spin - coated on glass substrates for optical (UV-VIS-NIR) analysis, and on ITO-coated glass substrates for electrochromic measurements. The samples are then annealed at 150 ° C for 1 hour. The resulting films have a yellow-orange color, typical of polycrystalline V{2}O{5}. The optical and physical constants (n, ? , Eg, the thickness d and the mean thickness inhomogeneity ? ) of the films are calculated using a simple and accurate method based on the transmission spectrum alone. Electrochromism of the films is studied using cyclic voltammetry (CV) in propylene carbonate solution containing 1 mol/1LiClO{4}. The films show reversible multichromism (yellow-green-blue) upon Li+ ion insertion/extraction. The absorbance of films colored at three different potentials is measured in the UV-VIS wavelength range, and this study shows that the changes in the optical absorption are consistent with the film color changes. Finally, the optical and electrochromic properties of the films prepared by this method are compared with those of the sputtered films already studied in our previous works.

Benmoussa, M.; Outzourhit, A.; Bennouna, A.; Ameziane, E. L.

2005-03-01

221

Non-aqueous electrochemical cell  

SciTech Connect

This patent describes a non-aqueous electrochemical cell. It comprises: an anode, a cathode and a non-aqueous electrolyte, the anode comprising a substrate having a mixture of at lease two elements selected from the group consisting of sodium, potassium, cesium and rubidium, and the anode having a skin or coating of an alkali metal.

Cipriano, R.A.

1992-02-04

222

Dynamics of proteins encapsulated in silica sol-gel glasses studied with IR vibrational echo spectroscopy.  

PubMed

Spectrally resolved infrared stimulated vibrational echo spectroscopy is used to measure the fast dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and -hemoglobin (HbCO) embedded in silica sol-gel glasses. On the time scale of approximately 100 fs to several picoseconds, the vibrational dephasing of the heme-bound CO is measurably slower for both MbCO and HbCO relative to that of aqueous protein solutions. The fast structural dynamics of MbCO, as sensed by the heme-bound CO, are influenced more by the sol-gel environment than those of HbCO. Longer time scale structural dynamics (tens of picoseconds), as measured by the extent of spectral diffusion, are the same for both proteins encapsulated in sol-gel glasses compared to that in aqueous solutions. A comparison of the sol-gel experimental results to viscosity-dependent vibrational echo data taken on various mixtures of water and fructose shows that the sol-gel-encapsulated MbCO exhibits dynamics that are the equivalent of the protein in a solution that is nearly 20 times more viscous than bulk water. In contrast, the HbCO dephasing in the sol-gel reflects only a 2-fold increase in viscosity. Attempts to alter the encapsulating pore size by varying the molar ratio of silane precursor to water (R value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady-state spectroscopic results. The vibrational echo data are discussed in the context of solvent confinement and protein-pore wall interactions to provide insights into the influence of a confined environment on the fast structural dynamics experienced by a biomolecule. PMID:16551107

Massari, Aaron M; Finkelstein, Ilya J; Fayer, Michael D

2006-03-29

223

Investigation of a new electrochemical cyanide sensor based on Ag nanoparticles embedded in a three-dimensional sol–gel  

Microsoft Academic Search

In this study, a novel sensor for cyanide detection was developed by self-assembling of a sol–gel network and silver nanoparticles. Silver doped silica nanocomposite was synthesized via a sol–gel technique combined with a nanoparticle preparing method. Then a cleaned gold electrode (GE) was immersed in a hydrolyzed mercaptopropyltrimethoxysilane (MPS) sol–gel solution containing Ag nanoparticles (AgNPs) to assemble three-dimensional silica gel.

Aboozar Taheri; Meissam Noroozifar; Mozhgan Khorasani-Motlagh

2009-01-01

224

A novel amperometric immunosensor based on three-dimensional sol–gel network and nanoparticle self-assemble technique  

Microsoft Academic Search

A novel hepatitis B surface antigen (HBsAg) immunosensor has been developed by self-assembling gold nanoparticles to a thiol-containing sol–gel network. A cleaned gold electrode was first immersed in a hydrolyzed mercaptopropyltrimethoxysilane (MPS) sol–gel solution to assemble three-dimensional silica gel, and then gold nanoparticles were chemisorbed onto the thiol groups of the sol–gel network. Finally, hepatitis B surface antibody (HBsAb) was

Ruping Liang; Jianding Qiu; Peixiang Cai

2005-01-01

225

Synthesis conditions for encapsulating cytochrome c and catalase in SiO 2 sol-gel materials  

Microsoft Academic Search

The encapsulation of biological molecules in sol-gel materials has led to the development of a new class of chemical and biomedical sensors. The influence of sol-gel synthesis conditions on the stability, chemical function, and enzymatic reactivity for horse heart cytochrome c and bovine liver catalase encapsulated in silica sol-gel materials was studied. The effects of synthesis pH, alcohol\\/alkoxide ratio, and

J. M. Miller; B. Dunn; J. S. Valentine; J. I. Zink

1996-01-01

226

Sol-gel nanocasting synthesis of patterned hierarchical LaFeO3 fibers with enhanced catalytic CO oxidation activity  

Microsoft Academic Search

Hierarchical LaFeO3 fibers were prepared by a sol-gel nanocasting method using a cotton cloth as the template. The resulting LaFeO3 fibers inherited the initial network morphology of the template very well and showed enhanced catalytic CO oxidation activity and satisfactory stability compared to the counterpart particles prepared by the conventional sol-gel method.Hierarchical LaFeO3 fibers were prepared by a sol-gel nanocasting

Pengna Li; Xianluo Hu; Lei Zhang; Hongxing Dai; Lizhi Zhang

2011-01-01

227

A comparative synthesis and physicochemical characterizations of Ni/Al2O3-MgO nanocatalyst via sequential impregnation and sol-gel methods used for CO2 reforming of methane.  

PubMed

Carbon dioxide reforming of methane is an interesting route for synthesis gas production especially over nano-sized catalysts. The present research deals with catalyst development for dry reforming of methane with the aim of reaching the most stable catalyst. Effect of preparation method, one of the most significant variables, on the properties of the catalysts was taken in to account. The Ni/Al2O3-MgO catalysts were prepared via sol-gel and sequential impregnation methods and characterized with XRD, FESEM, EDAX, BET and FTIR techniques. The reforming reactions were carried out using different feed ratios, gas hourly space velocities (GHSV) and reaction temperatures to identify the influence of operational variables. FESEM images indicate uniform particle size distribution for the sample synthesized with sol-gel method. It has been found that the sol-gel method has the potential to improve catalyst desired properties especially metal surface enrichment resulting in catalytic performance enhancement. The highest yield of products was obtained at 850 degrees C for both of the catalysts. During the 10 h stability test, CH4 and CO2 conversions gained higher values in the case of sol-gel made catalyst compared to impregnated one. PMID:23901507

Aghamohammadi, Sogand; Haghighi, Mohammad; Karimipour, Samira

2013-07-01

228

Sol-Gel Synthesis of Fluoride Glasses and Thin Films: the Effects of Processing on the Chemical, Physical, Optical, and Rare Earth Fluorescence Properties of Sol - Zbla Glasses.  

NASA Astrophysics Data System (ADS)

Fluoride glasses have the potential to be ultra -low loss optical fiber and active optical devices due to their intrinsic clarity, wide transmission window, and low phonon energy. Unfortunately, conventional processing methods have failed to produce defect free glasses, fibers, or thin films. However, sol-gel techniques offer high purity, low temperature processing routes conducive to high quality optics. Thus, a modified sol-gel technique was investigated as an alternative approach for fluoride glass production. Hydrous oxide gels and thin films were prepared by hydrolyzing an alcoholic solution of alkoxides and hydroxides. Subsequent fluorination of the gels in gaseous hydrogen fluoride led to the successful formation of ZBLA (rm 57ZrF _4-36BaF_2-4LaF _3-3AlF_3, in mol%) fluoride glasses. However, the resulting glasses had inferior optical properties. The thermal processing and analysis of these materials was then studied to determine the cause of the poor transparency and to find a remedy. The poor transparency of the sol-gel fluoride glasses was due to residual organics that led to carbon and reduced zirconium species that were strongly absorbing. However, optical quality glasses could be produced by removing these contaminants via treatment with a high temperature oxidizing atmosphere such as NF_3 or SF _6 without introducing other contaminants such as oxygen. The resulting glasses had chemical, electrical, mechanical, and optical properties commensurate with conventionally prepared glasses. It was also found that hydrocarbon contamination could be avoided altogether by using an inorganic sol-gel process involving the polymerization of zirconium hydroxychloride salts. To study the gel structure and local environment of rare earth dopants during thermal processing and conversion of the gel, Eu^{3+} fluorescence spectroscopy was employed. The Eu^{3+ } fluorescence revealed a change in site symmetry and decrease in host phonon energy upon fluorination. In addition to the well known red Eu^{3+ } luminescence, ultraviolet, blue, and green emissions were also observed in fluoride glasses and discovered to be concentration dependent. The Eu^ {3+} fluorescence was concluded to be a good probe for evaluating sol-gel fluoride materials and that the concentration dependence of the high energy emissions of Eu^{3+} was due to electric dipole-dipole and dipole-quadrupole cross relaxations.

Dejneka, Matthew J.

1995-01-01

229

Room temperature sol-gel fabrication and functionalization for sensor applications  

NASA Astrophysics Data System (ADS)

The structure and physical properties of a thin titania sol-gel layer prepared on silicon and silica surfaces were examined. Spectroscopic (FTIR, UV-VIS spectroscopy), refractive index (ellipsometry) and microscopic (light microscopy and SEM/EDS) tools were used to examine both chemical uniformity and physical uniformity of the sol-gel glass layers. The conditions for the fabrication of uniform layers were established, and room temperature dopant incorporation was examined. The absorption bands of porphyrin-containing titania sol-gel layers were characterized. By addition of a metal salt to the titania layer, it was possible to metallate the free-base porphyrin within and change the UV-VIS absorbance of the porphyrin, the basis of metal detection using porphyrins. The metalloporphyrins were detected by localized laser ablation inductive coupled mass spectroscopy (LA-ICP-MS), indicating fairly uniform distribution of metals across the titania surface.

Huyang, George; Canning, John; Petermann, Ingemar; Bishop, David; McDonagh, Andrew; Crossley, Maxwell J.

2013-06-01

230

High-energy-density sol-gel thin film based on neat 2-cyanoethyltrimethoxysilane.  

PubMed

Hybrid organic-inorganic sol-gel dielectric thin films from a neat 2-cyanoethyltrimethoxysilane (CNETMS) precursor have been fabricated and their permittivity, dielectric strength, and energy density characterized. CNETMS sol-gel films possess compact, polar cyanoethyl groups and exhibit a relative permittivity of 20 at 1 kHz and breakdown strengths ranging from 650 V/?m to 250 V/?m for film thicknesses of 1.3 to 3.5 ?m. Capacitors based on CNETMS films exhibit extractable energy densities of 7 J/cm(3) at 300 V/?m, as determined by charge-discharge and polarization-electric field measurements, as well as an energy extraction efficiency of ~91%. The large extractable energy resulting from the linear dielectric polarization behavior suggests that CNETMS films are promising sol-gel materials for pulsed power applications. PMID:23427818

Kim, Yunsang; Kathaperumal, Mohanalingam; Smith, O'Neil L; Pan, Ming-Jen; Cai, Ye; Sandhage, Kenneth H; Perry, Joseph W

2013-03-13

231

Characterisation of bismuth-doped yttrium iron garnet layers prepared by sol-gel process  

NASA Astrophysics Data System (ADS)

Yttrium iron garnets and Bi-substituted yttrium iron garnets were prepared by two different sol-gel processes. We investigated the evolution with temperature of XRD patterns and of the magnetisation of powders issued from sol-gel solution decomposition. We prepared layers on silica glass by the spin- or dip-coating processes. XRD patterns on layers were also obtained. The dependency of the Faraday effect upon the light wavelength and Bi amount was shown. The main result is the possibility to prepare stable sol-gel solutions containing bismuth, yttrium and iron precursors which lead to garnet phase after annealing at low temperature. These bismuth-doped garnet phases give the expected magneto-optical properties. These processes are promising for the preparation of inexpensive magneto-optical recording media.

Rehspringer, J.-L. J.-L.; Bursik, J.; Niznansky, D.; Klarikova, A.

2000-03-01

232

Influence of pyrogenic particles on the micromechanical behavior of thin sol-gel layers.  

PubMed

Coatings based on sol-gel technology with different types of nanoparticles embedded into the sol-gel matrix were fabricated, and the resulting properties were investigated. Pyrogenic silica nanoparticles were added to the sol before coating. The silica particles varied in primary particle size and agglomerate size, and in their surface modification. The particles were wetted in ethanol and dispersed to certain finenesses. The difference in agglomerate size was partly caused by varying particle types, but also by the dispersing processes that were applied to the particles. The resulting coatings were examined by visual appearance and SEM microscopy. Furthermore, their micromechanical properties were determined by nanoindentation. The results show an important influence from the added nanoparticles and their properties on the visual appearance as well as the micromechanical behavior of the sol-gel coatings. It is shown that, in fact, the particle size distribution can have a major impact on the coating properties as well as the surface modification. PMID:21630652

Schönstedt, B; Garnweitner, G; Barth, N; Mühlmeister, A; Kwade, A

2011-07-01

233

Optical activation of Si nanowires using Er-doped, sol-gel derived silica  

SciTech Connect

Optical activation of Si nanowires (Si-NWs) using sol-gel derived Er-doped silica is investigated. Si-NWs of about 100 nm diameter were grown on Si substrates by the vapor-liquid-solid method using Au catalysts and H{sub 2} diluted SiCl{sub 4}. Afterwards, Er-doped silica sol-gel solution was spin-coated, and annealed at 950 deg. C in flowing N{sub 2}/O{sub 2} environment. Such Er-doped silica/Si-NWs nanocomposite is found to combine the advantages of crystalline Si and silica to simultaneously achieve both high carrier-mediated excitation efficiency and high Er{sup 3+} luminescence efficiency while at the same time providing high areal density of Er{sup 3+} and easy current injection, indicating the possibility of developing sol-gel activated Si-NWs as a material platform for Si-based photonics.

Suh, Kiseok; Shin, Jung H.; Park, Oun-Ho; Bae, Byeong-Soo; Lee, Jung-Chul; Choi, Heon-Jin [Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon (Korea, Republic of); Department of Materials Science and Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon (Korea, Republic of); Materials Science and Technology Division, Korea Institute of Science and Technology (KIST), P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); School of Advanced Materials Science and Engineering, Yonsei University, Yonsei, 120-74 (Korea, Republic of)

2005-01-31

234

Ultrapure glass optical waveguide development in microgravity by the sol-gel process  

NASA Technical Reports Server (NTRS)

Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process referred to here is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation. The use of gels offers several advantages such as high purity and lower melting times and temperatures. The sol-gel process is studied for utilization in the preparation of multicomponent ultrapure glass batches for subsequent containerless melting of the batches in space to prepare glass blanks for optical waveguides.

Mukherjee, S. P.; Holman, R. A.

1981-01-01

235

Thin film porous membranes based on sol-gel chemistry for catalytic sensors  

SciTech Connect

Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel films have little effect on the sensing response to H{sub 2} alone. However, in the presence of other gases, the nanoporous film modifies the sensor behavior in several beneficial ways. (1) They have shown that the sol-gel coated sensors were only slightly poisoned by high concentrations of H{sub 2}S while uncoated sensors showed moderate to severe poisoning effects. (2) For a given partial pressure of H{sub 2}, the signal from the sensor is modified by the presence of O{sub 2} and other oxidizing gases.

Hughes, R.C.; Patel, S.V.; Jenkins, M.W.; Boyle, T.J.; Gardner, T.J.; Brinker, C.J.

1998-05-01

236

Optical activation of Si nanowires using Er-doped, sol-gel derived silica  

NASA Astrophysics Data System (ADS)

Optical activation of Si nanowires (Si-NWs) using sol-gel derived Er-doped silica is investigated. Si-NWs of about 100 nm diameter were grown on Si substrates by the vapor-liquid-solid method using Au catalysts and H2 diluted SiCl4. Afterwards, Er-doped silica sol-gel solution was spin-coated, and annealed at 950 °C in flowing N2/O2 environment. Such Er-doped silica/Si-NWs nanocomposite is found to combine the advantages of crystalline Si and silica to simultaneously achieve both high carrier-mediated excitation efficiency and high Er3+ luminescence efficiency while at the same time providing high areal density of Er3+ and easy current injection, indicating the possibility of developing sol-gel activated Si-NWs as a material platform for Si-based photonics.

Suh, Kiseok; Shin, Jung H.; Park, Oun-Ho; Bae, Byeong-Soo; Lee, Jung-Chul; Choi, Heon-Jin

2005-01-01

237

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.  

PubMed

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses. PMID:23171477

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

238

Sol-gel deposited electrochromic films for electrochromic smart window glass  

SciTech Connect

Electrochromic windows offer the ability to dynamically change the transmittance of a glazing. With the appropriate sensor and controls, this smart window can be used for energy regulation and glare control for a variety of glazing applications. The most promising are building and automotive applications. This work covers the use of sol-gel deposition processes to make active films for these windows. The sol-gel process offers a low-capital investment for the deposition of these active films. Sol-gel serves as an alternative to more expensive vacuum deposition processes. The sol-gel process utilizes solution coating followed by a hydrolysis and condensation. In this investigation the authors report on tungsten oxide and nickel oxide films made by the sol-gel process for electrochromic windows. The properties of the sol-gel films compare favorably to those of films made by other techniques. A typical laminated electrochromic window consists of two glass sheets coated with transparent conductors, which are coated with the active films. The two sheets are laminated together with an ionically conductive polymer. The range of visible transmission modulation of the tungsten oxide was 60% and for the nickel oxide was 20%. The authors used the device configuration of glass/SnO{sub 2}:F/W0{sub 3}/polymer/Li{sub Z}NiO{sub x}H{sub y}/SnO{sub 2}:F glass to test the films. The nickel oxide layer had a low level of lithiation and possibly contained a small amount of water. Lithiated oxymethylene-linked poly(ethylene oxide) was used as the laminating polymer. Commercially available SnO{sub 2}:F/glass (LOF-Tec glass) was used as the transparent conducting glass. The authors found reasonable device switching characteristics which could be used for devices.

Oezer, N. [Istanbul Univ. (Turkey). Faculty of Science; Lampert, C.M. [Star Science (United States); Rubin, M. [Lawrence Berkeley National Lab., CA (United States). Environmental Energy Technologies Div.

1996-08-01

239

Novel Sol-Gel Based Pt Nanocluster Catalysts for Propane Dehydrogenation  

SciTech Connect

We report propane dehydrogenation behavior of catalysts prepared using two novel synthesis strategies that combine inverse micelle Pt nanocluster technology with silica and alumina sol-gel processing. Unlike some other sol-gel catalyst preparations. Pt particles in these catalysts are not encapsulated in the support structure and the entire Pt particle surface is accessible for reaction. Turnover frequencies (TOF) for these catalysts are comparable to those obtained over Pt catalysts prepared by traditional techniques such as impregnation, yet the resistance to deactivation by carbon poisoning is much greater in our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.

Boespflug, Elaine; Kawola, Jeffrey S.; Martino, Anthony; Sault, Allen G.

1999-08-09

240

Silver doped YBCO coated conductor development by sol-gel process  

Microsoft Academic Search

The nonfluorinated YBa2Cu3O7-x (YBCO) coated conductors with 1-3 wt%Ag have been fabricated by sol-gel process. Ag doped YBCO films were fabricated on CeO2\\/YSZ\\/CeO2 buffer layered Ni tapes by continuous sol-gel dip coating process. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analysis were used to characterize the YBCO coated conductor. The superconducting properties (Tc and Jc) of Ag doped YBCO

Z. Aslanoglu; Y. Akin; M. I. El-Kawni; L. Arda; W. Sigmund; Y. S. Hascicek

2003-01-01

241

Sol-gel-derived alumina-supported copper oxide sorbent for flue gas desulfurization  

Microsoft Academic Search

Nanostructured mesoporous CuO\\/γ-AlâOâ granular sorbents were prepared by the sol-gel method. Performance of the sol-gel-derived CuO\\/γ-AlâOâ sorbents for SOâ removal was studied in a fixed-bed adsorption system. SOâ breakthrough curves with a feed stream of air containing 2000 ppm SOâ were measured at different temperatures (300--500 C) and flow rates (interstitial velocity of 0.25--6.96 cm\\/s). The optimum sulfation and regeneration

Zhong-Min Wang; Y. S. Lin

1998-01-01

242

Site selective generation of sol-gel deposits in layered bimetallic macroporous electrode architectures.  

PubMed

The elaboration of an original composite bimetallic macroporous electrode containing a site-selective sol-gel deposit is reported. Regular colloidal crystals, obtained by a modified Langmuir-Blodgett approach, are used as templates for the electrogeneration of the desired metals in the form of a well-defined layered bimetallic porous electrode. This porous matrix shows a spatially modulated electroactivity which is subsequently used as a strategy for targeted electrogeneration of a sol-gel deposit, exclusively in one predefined part of the porous electrode. PMID:22260622

Lalo, Hélène; Bon-Saint-Côme, Yémima; Plano, Bernard; Etienne, Mathieu; Walcarius, Alain; Kuhn, Alexander

2012-02-01

243

Sol-gel derived nanostructured cerium oxide film for glucose sensor  

Microsoft Academic Search

Sol-gel derived nanostructured cerium oxide (CeO2) film deposited on gold (Au) electrode has been utilized for physisorption of glucose oxidase (GOx). X-ray diffraction, atomic force microscopy, UV-visible spectroscopy, and electrochemical techniques have been used to characterize sol-gel derived CeO2?Au electrode and GOx?CeO2?Au bioelectrode. The response characteristics of the glucose bioelectrode (GOx?CeO2?Au) indicate linearity, detection limit and shelf-life as 50–400 mg?dL,

Anees A. Ansari; Pratima R. Solanki; B. D. Malhotra

2008-01-01

244

Sol-gel derived nanostructured cerium oxide film for glucose sensor  

Microsoft Academic Search

Sol-gel derived nanostructured cerium oxide (CeO2) film deposited on gold (Au) electrode has been utilized for physisorption of glucose oxidase (GOx). X-ray diffraction, atomic force microscopy, UV-visible spectroscopy, and electrochemical techniques have been used to characterize sol-gel derived CeO2\\/Au electrode and GOx\\/CeO2\\/Au bioelectrode. The response characteristics of the glucose bioelectrode (GOx\\/CeO2\\/Au) indicate linearity, detection limit and shelf-life as 50-400 mg\\/dL,

Anees A. Ansari; Pratima R. Solanki; B. D. Malhotra

2008-01-01

245

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

NASA Astrophysics Data System (ADS)

Sol-gel silica thin films embedding an ytterbium quinolinolato complex (YbClQ4) have been obtained using different alkoxides. Homogeneous, crack- and defect-free thin films of optical quality have been successfully deposited on glass substrate by dip-coating. The silica thin films have been characterized by time-resolved photoluminescence. The luminescence properties of the YbClQ4 are preserved in silica films prepared through an optimized sol-gel approach. The excited state lifetime of the lanthanide is comparable to those observed in bulk and longer than the corresponding ones in solution.

Figus, Cristiana; Quochi, Francesco; Artizzu, Flavia; Piana, Giacomo; Saba, Michele; Mercuri, Maria Laura; Serpe, Angela; Deplano, Paola; Mura, Andrea; Bongiovanni, Giovanni

2014-10-01

246

Polymer-Titanium hybrids obtained by radical polymerization and Sol-Gel process  

Microsoft Academic Search

The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and\\/or poly(ethyl\\u000a acrylate) (PEtA) with TiO2 was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved\\u000a simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl\\u000a acetoacetate (AlAcAc), was used. Covalent bonds between

Dan Donescu; Sever Serban; Kristiana Gosa; Cristian Petcu

2005-01-01

247

Piezoelectric thick film ultrasonic transducers fabricated by a sol-gel spray technique.  

PubMed

Thick film broadband ultrasonic transducers (UTs) produced by a sol-gel spray technique and operated below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol-gel solution. The 50-100 microm thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a signal to noise ratio of more than 25 dB are experimentally obtained for the operating temperatures up to 250 degrees C. PMID:12479598

Kobayashi, M; Olding, T R; Sayer, M; Jen, C K

2002-10-01

248

The sol-gel entrapment of noble metals in hybrid silicas: a molecular insight  

PubMed Central

Background Why are metal nanoparticles sol-gel entrapped in ORMOSIL so active and stable? In other words, why ORMOSIL-entrapped metal nanoparticles are more active and selective than many heterogenized counterparts, including silica-entrapped noble metals? Results Unveiling specific interactions between MNPs and the molecular structure of ORMOSIL, this work investigates subtle structural aspects through DRIFT spectroscopy. Conclusions The results point to interactions between entrapped Pd and Pt nanocrystallites with the organosilica sol-gel cages similar to those taking place in enzymes. PMID:24079552

2013-01-01

249

Characterization of Sol-Gel derived scintillating LuBO3 films doped with rare earth ions.  

E-print Network

Characterization of Sol-Gel derived scintillating LuBO3 films doped with rare earth ions. C. Mansuy-669" DOI : 10.1016/j.tsf.2005.12.235 #12;Abstract Rare earth doped LuBO3 thin films have been prepared, 81.20. Fw, Keywords : Sol-Gel, Scintillators, XPS, RBS, Rare earth ions, Luminescence hal-00154764

Boyer, Edmond

250

Electrochemical and In Vitro Behavior of Nanostructure Sol-Gel Coated 316L Stainless Steel Incorporated with Rosemary Extract  

NASA Astrophysics Data System (ADS)

The corrosion resistance of AISI 316L stainless steel for biomedical applications, was significantly enhanced by means of hybrid organic-inorganic sol-gel thin films deposited by spin-coating. Thin films of less than 100 nm with different hybrid characters were obtained by incorporating rosemary extract as green corrosion inhibitor. The morphology, composition, and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX, and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 21.2 MPa for the hybrid sol-gel coating. The effect of rosemary extract, with various added concentrations from 0.012 to 0.1%, on the anticorrosion properties of sol-gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Rosemary extract additions (0.05%) have significantly increased the corrosion protection of the sol-gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol-gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol-gel thin films are practical hybrid films in biomedical applications.

Motalebi, Abolfazl; Nasr-Esfahani, Mojtaba

2013-06-01

251

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

EPA Science Inventory

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...

252

Sol–gel synthesis and lithium ion conduction properties of garnet-type Li{sub 6}BaLa{sub 2}Ta{sub 2}O{sub 12}  

SciTech Connect

Graphical abstract: Li{sub 6}BaLa{sub 2}Ta{sub 2}O{sub 12}, prepared by sol–gel synthesis method, shows a total Li-ion conductivity of 1.69 × 10{sup ?5} S/cm at 298 K and an activation energy is 0.40 eV. Highlights: ? Garnet-type fast ion conductor LLBTO was synthesized by modified sol–gel Pechini method. ? The synthesis temperature is significantly lower (200 K) than conventional solid state synthesis methods. ? The ionic conductivity of sol–gel synthesized LLBTO is 1.69 × 10{sup ?5} S/cm. -- Abstract: High lithium ion conductive garnet-type barium lanthanum lithium tantalate, Li{sub 6}BaLa{sub 2}Ta{sub 2}O{sub 12} (LLBTO), was prepared by a modified sol–gel Pechini method from the appropriate mixtures of lithium carbonate, lanthanum oxide, barium carbonate and tantalum ethoxide. The thermal decomposition of the precursor powder was investigated by TG/DTA analysis. The LLBTO precursor powders were annealed at various temperatures between 923 and 1123 K for 6 h in air. The transformation process from precursor powder to crystalline garnet-like phase was analyzed by X-ray powder diffraction (XRPD). The morphology of the powders annealed at various temperatures was investigated by scanning electron microscopy (SEM). The resultant pelletized Li{sub 6}BaLa{sub 2}Ta{sub 2}O{sub 12}, prepared by sol–gel synthesis method, shows a total Li-ion conductivity of 1.69 × 10{sup ?5} S/cm at 298 K and an activation energy is 0.40 eV. The ionic conductivities reported in this study are slightly higher than those reported for LLBTO sample synthesized by conventional solid state synthesis route.

Kokal, I., E-mail: i.kokal@tue.nl [Energy Materials and Devices, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Ramanujachary, K.V. [Department of Chemistry and Biochemistry, Rowan University, Glassboro, New Jersey, NJ 08028 (United States)] [Department of Chemistry and Biochemistry, Rowan University, Glassboro, New Jersey, NJ 08028 (United States); Notten, P.H.L.; Hintzen, H.T. [Energy Materials and Devices, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)] [Energy Materials and Devices, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)

2012-08-15

253

Novel potentiometric immunosensor for determination of diphtheria antigen based on compound nanoparticles and bilayer two-dimensional sol–gel as matrices  

Microsoft Academic Search

A novel method for fabrication of a diphtheria potentiometric immunosensor has been developed by means of self-assembling compound nanoparticles to a thiol-containing sol–gel network. A cleaned gold electrode was first immersed in a 3-mercaptopropyltrimethoxysilane (MPS) sol–gel solution to assemble a silica sol–gel monolayer. The silane entities were then polymerized into a two-dimensional sol–gel network (2D network) by dipping into aqueous

Dianping Tang; Ruo Yuan; Yaqin Chai; Yan Liu; Jianyuan Dai; Xia Zhong

2005-01-01

254

The growth of LiNbO 3 (0 0 6) on MgO (0 0 1) and LiTaO 3 (0 1 2) substrates by sol–gel procedure  

Microsoft Academic Search

LiNbO3 films, which were based on a non-hydrolytic sol–gel route, were deposited on LiTaO3 (012) and MgO (001) substrates. After drying, thin films with amorphous structure were obtained. During heat treatment followed by drying, amorphous structure changed into crystalline structure. Both cases of LiNbO3 films showed high orientation of LiNbO3 (006) planes as well as other orientations. The influences of

Ryoung-Han Kim; Hyung-Ho Park; Gi-Tae Joo

2001-01-01

255

Non-Aqueous Capillary Electrophoresis  

NASA Astrophysics Data System (ADS)

Non-aqueous capillary electrophoresis and capillary electrochromatography are special variants of these techniques. Here, organic solvents or their mixtures with or without dissolved electrolytes are used as separation buffer or mobile phase, respectively. The most important features of non-aqueous systems are: better solubility of more hydrophobic ionic substances (many natural products) than in water, much less current and Joule heating allows for using highly concentrated buffers and/or larger capillary internal diameters, polar interactions are enhanced in organic solvents which is often highly advantageous in chiral separation systems. This chapter presents most frequently used solvents, their properties, as well as shows pH* scale which is often used in non-aqueous systems.

Szumski, Micha?; Buszewski, Bogus?aw

256

Enzyme Stabilization by Covalent Binding in Nanoporous Sol-Gel Glass for  

E-print Network

Enzyme Stabilization by Covalent Binding in Nanoporous Sol-Gel Glass for Nonaqueous Biocatalysis mate- rial for enzyme immobilization. A model enzyme, -chy- motrypsin, was efficiently bound onto the glass via a bifunctional ligand, trimethoxysilylpropanal, with an ac- tive enzyme loading of 0.54 wt

Wang, Ping

257

Exploring the synthesis and characterization of nanoenergetic materials from sol-gel chemistry  

Microsoft Academic Search

Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed 'proton scavenging' mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide\\/hydroxide,

Jeremy D. Walker

2007-01-01

258

Sol-gel chemical sensors for surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection. Unfortunately, the inability of SERS to perform quantitative chemical analysis has slowed its general use in laboratories. This is largely due to the difficulty of manufacturing either active surfaces that yield reproducible enhancements, or surfaces that are capable of reversible chemical adsorption, or both. In an effort to meet this need, we have developed metal-doped sol-gels that provide surface-enhancement of Raman scattering. The porous silica network offers a unique environment for stabilizing SER active metal particles and the high surface area increases the interaction between the analyte and metal particles. This eliminates the need to concentrate the analyte on the surface by evaporating the solvent. The sol-gel is easily coated on a variety of surfaces, such as fiber optics, glass slides, or glass tubing, and can be designed into sample flow systems. Here we present the development of both gold- and silver-doped sol-gels, which have been used to coat the inside walls of glass sample vials for SERS applications. The performance of the metal-doped sol-gels was evaluated using p-aminobenzoic acid, to establish enhancement factors, detection limits, dynamic response range, reversibility, reproducibility, and suitability to commercial spectrometers. Measurements of trace chemicals, such as adenine and cocaine, are also presented.

Lee, Vincent Y.; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

1999-02-01

259

Copper loaded on sol-gel-derived alumina adsorbents for phosphine removal.  

PubMed

The hydride gas of phosphine (PH3) is commonly used for semiconductor and optoelectronic industries. The local scrubbers must immediately abate it because of its high toxicity. In this study, copper (Cu) loaded on the sol-gel-derived gamma-alumina (Al2O3) adsorbents are prepared and tested to investigate the possibility of PH3 removal and sorbent regeneration. Test results showed that during the breakthrough time of over 99% PH3 removal efficiency, the maximum adsorption capacity of Cu loaded on the sol-gel-derived gamma-Al2O3 adsorbent is 18 mg-PH3/g-adsorbent. This is much higher than that of Cu loaded on the commercial gamma-Al2O3 adsorbent--8.6 mg-PH3/g-adsorbent. The high specific surface area, narrow pore size distribution, and well dispersion of Cu loaded on the sol-gel-derived gamma-Al2O3 could be the reasons for its high PH3 adsorption capacity. The regeneration test shows that Cu loaded on the sol-gel-derived gamma-Al2O3 adsorbent can be regenerated after a simple air purging procedure. The cumulative adsorption capacity for five regeneration cycles is 65 mg-PH3/g-adsorbent, which is approximately double that of the Cu/zeolite adsorbent demonstrated in the literature. PMID:20480862

Hsu, Jung-Nan; Bai, Hsunling; Li, Shou-Nan; Tsai, Chuen-Jinn

2010-05-01

260

Graded-index antireflective coatings for high power lasers deposited by sol-gel process  

NASA Astrophysics Data System (ADS)

Gradient index alkali borosilicate antireflection films for use in laser systems were deposited by the sol-gel process. It is found that laser damage thresholds of these films, measured with 1.07 micro m, 1 ns pulses are four times greater than thresholds of widely used, multilayer, antireflection coatings.

Lowdermilk, W. H.; Mukherjee, S. P.

1981-11-01

261

Mullite interaction with bismuth oxide from minerals and sol-gel processes F. Gridi-Bennadji *  

E-print Network

Mullite interaction with bismuth oxide from minerals and sol-gel processes F. Gridi-Bennadji * , J doped by bismuth oxide was studied by TGA and DTA, X ray diffraction, and electron microscopy (SEM and mullite, glass and Al- rich oxides are formed. Mullite exhibits an accentuated acicular morphology along 3

Paris-Sud XI, Université de

262

Enhanced Proteolytic Activity of Covalently Bound Enzymes in Photopolymerized Sol Gel  

E-print Network

Enhanced Proteolytic Activity of Covalently Bound Enzymes in Photopolymerized Sol Gel Maria T (BAEE) and two peptides, neuro- tensin and insulin chain B. The coupling of the enzyme to the monolith functional group links to an inactive amine on trypsin to form an imine bond. The proteolytic activity

Zare, Richard N.

263

Analysis and theory of gas transport in microporous sol-gel derived ceramic membranes  

Microsoft Academic Search

Sol-gel modification of mesoporous alumina membranes is a very successful technique to improve gas separation performance. Due to the formed microporous top layer, the membranes show activated transport and molecular sieve-like separation factors. This paper concentrates on the mechanism of activated transport (also often referred to as micropore diffusion or molecular sieving). Based on a theoretical analysis, results from permeation

R. S. A. de Lange; K. Keizer; A. J. Burggraaf

1995-01-01

264

The influence of surfactants on the roughness of titania sol-gel films  

SciTech Connect

Substrate dipping in a composite sol-gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO{sub 2}) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol-gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV-vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO{sub 2} film was obtained with a short immersion of fiberglass into the sol-gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 deg. C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO{sub 2} films prepared from the sol-gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 {mu}m. Smooth TiO{sub 2} films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO{sub 2} films can enhance the inherent photocatalytic activity.

Medina-Valtierra, Jorge [Departamento de Ingenieria Quimica y Bioquimica, Instituto Tecnologico de Aguascalientes, Av. A. Lopez Mateos Ote. No. 1801, Fracc. Bona Gens, Aguascalientes 20256 (Mexico)]. E-mail: jormeval@yahoo.com; Frausto-Reyes, Claudio [Centro de Investigaciones en Optica A.C., Loma del Bosque No. 115, Col. Lomas del Campestre, Leon, Gto. 37150 (Mexico)]. E-mail: cfraus@cio.mx; Calixto, Sergio [Centro de Investigaciones en Optica A.C., Loma del Bosque No. 115, Col. Lomas del Campestre, Leon, Gto. 37150 (Mexico)]. E-mail: scalixto@cio.mx; Bosch, Pedro [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, Cd. Universitaria, Mexico, D.F. 04510 (Mexico)]. E-mail: croqcroqcroq@yahoo.com; Hugo Lara, Victor [Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico, D.F. 09340 (Mexico)]. E-mail: lacv@xanum.uam.mx

2007-03-15

265

The effect of silica-coating by sol-gel process on resin-zirconia bonding.  

PubMed

The effect of silica-coating by sol-gel process on the bond strength of resin composite to zirconia was evaluated and compared against the sandblasting method. Four groups of zirconia samples were silica-coated by sol-gel process under varied reagent ratios of ethanol, water, ammonia and tetraethyl orthosilicate and for different deposition times. One control group of zirconia samples were treated with sandblasting. Within each of these five groups, one subgroup of samples was kept in dry storage while another subgroup was aged by thermocycling for 6,000 times. Besides shear bond testing, the surface topography and surface elemental composition of silica-coated zirconia samples were also examined using scanning electron microscopy and X-ray photoelectron spectroscopy. Comparison of silica coating methods revealed significant differences in bond strength among the Dry groups (p<0.001) and Thermocycled groups (p<0.001). Comparison of sol-gel deposition times also revealed significant differences in bond strength among the Dry groups (p<0.01) and Thermocycled groups (p<0.001). Highest bond strengths were obtained after 141-h deposition: Dry (7.97±3.72 MPa); Thermocycled (2.33±0.79 MPa). It was concluded that silica-coating of zirconia by sol-gel process resulted in weaker resin bonding than by sandblasting. PMID:23370886

Lung, Christie Ying Kei; Kukk, Edwin; Matinlinna, Jukka Pekka

2013-01-01

266

Encapsulation of the ferritin protein in sol-gel derived silica glasses  

Microsoft Academic Search

A significant recent development in sol-gel science has been the encapsulation of biomolecules such as proteins and enzymes in optically transparent silica glasses. This paper reports on the encapsulation of an iron (Fe) storage protein, ferritin, to develop a magnetic silica glass. Native ferritin, which has a nanometer-sized microcrystalline Fe oxide core, was encapsulated in optically transparent silica glasses using

Esther H. Lan; Bruce Dunn; Joan Selverstone Valentine; Jeffrey I. Zink

1996-01-01

267

Raman Spectra of Molecules Adsorbed on Ag Centers in Sol-Gel Matrices  

Microsoft Academic Search

Silica monoliths and submicron spheres containing silver nanoparticles have been obtained using the sol gel technology. The Ag inclusions were synthesized via the counterdiffusion method. The silver-doped matrices were immersed in solutions of an organic dye (indocyanine green) enabling the solute molecules to interact with surface of the Ag-doped silica matrices. Raman spectra of free solutions of the organic molecules

Krzysztof Maruszewski; Marek Jasiorski; Dariusz Hreniak; Wies?aw Str?k; Krzysztof Hermanowicz; Krystyna Heiman

2003-01-01

268

Analysis of sol gel silica titania films doped with Ag and Er using artificial neural networks  

Microsoft Academic Search

Sol gel processing is a cheap and versatile method of producing silica on silicon films for planar integrated optics. It leads to high Er incorporation and to easy incorporation of Ag, that can intensify the rare-earth photoluminescence. Different heat treatments and compositions must be tested to optimise the properties of the films grown, and the annealing may lead to redistribution

N. R. Nené; A. Vieira; A. C. Marques; R. M. Almeida; A. R. Ramos; E. Alves; N. P. Barradas

2006-01-01

269

Ellipsometric spectroscopy study of cobalt oxide thin films deposited by sol–gel  

Microsoft Academic Search

Due to their unique optical properties, solar selective coatings enhance the thermal efficiency of solar photothermal converters. Hence it seems to be interesting to study the optical properties of promising materials as solar selective coatings. In an earlier work, it was demonstrated that sol–gel deposited cobalt oxide thin films possess suitable optical properties as selective coatings. In this work, cobalt

E. Barrera-Calva; J. C. Martínez-Flores; L. Huerta; A. Avila; M. Ortega-López

2006-01-01

270

Graded Index Sol-Gel Antireflection Coatings , Jonathan Grandidier1,2  

E-print Network

adjusted so that the refractive indices are tunable from n=1.1 to n=1.5. Reflectance measurements also show that reflectivity decreases across the entire spectrum with added sol- gel multilayers. Index Terms -- Solgel hydrolysis and condensation reactions to transform a colloidal solution into a solid network (gel) (Figure 1

Grandidier, Jonathan

271

Low-density nanoporous iron foams synthesized by sol-gel autocombustion  

PubMed Central

Nanoporous iron metal foams were synthesized by an improved sol-gel autocombustion method in this report. It has been confirmed to be pure phase iron by X-ray diffraction measurements. The nanoporous characteristics were illustrated through scanning electron microscope and transmission electron microscope images. Very low density and quite large saturation magnetization has been performed in the synthesized samples. PMID:22333555

2012-01-01

272

DEVELOPMENT OF A FABRICATION PROCESS FOR SOL-GEL\\/METAL HYDRIDE COMPOSITE GRANULES  

Microsoft Academic Search

An external gelation process was developed to produce spherical granules that contain metal hydride particles in a sol-gel matrix. Dimensionally stable granules containing metal hydrides are needed for applications such as hydrogen separation and hydrogen purification that require columns containing metal hydrides. Gases must readily flow through the metal hydride beds in the columns. Metal hydrides reversibly absorb and desorb

E Hansen; E Eric Frickey; L Leung Heung

2004-01-01

273

Characterization of boria-alumina mixed oxides prepared by a sol-gel method.  

E-print Network

of aluminum tri-sec-butoxide in presence of (NH4)2BB 4O7.4H2O. Then, the solid-state magic angle spinning NMRCharacterization of boria-alumina mixed oxides prepared by a sol- gel method. Part 1: NMR constituted of octahedral aluminum species. Al O Al Boehmite matrix: Octahedral alumina species arrangement O

Paris-Sud XI, Université de

274

Fabrication of gratings and design of diffractive optical elements embossed on sol-gel films  

NASA Astrophysics Data System (ADS)

Ion exchange, plasma deposition and flame hydrolysis are typically employed techniques for fabricating glass waveguides and gratings. These techniques have several drawbacks such as involvement of expensive instruments, multi-step procedure and high temperature treatment. These drawbacks make it difficult for their adoption mass production. The sol-gel process is a simple and inexpensive way for making glass, and embossing into sol-gel films provides a simple alternative for fabricating surface profile gratings and other integrated optical devices. In this paper, we report the usage of the embossing technique to fabricate gratings and diffractive optical elements (DOEs) in the sol-gel cladding layer of a waveguide. The designed DOEs manipulate out-coupled light from a slab waveguide and form 3 lines of equal intensity at a stipulated distance. The DOEs were designed as two-level optics by the direct binary search method based on the scalar diffractive theory, and the master molders used in the embossing were fabricated by UV laser writing on photoresist combined with reactive ion etching. We chose organic modified silane in the sol-gel process and no baking was needed, greatly minimizing possible shrinkage of the thin film.

Tan, Gu; Chan, Yuen Chuen; Liu, Jian; Liaw, ChinYi; Lam, Yee Loy; Zhou, Yan

1999-11-01

275

Sol-gel glasses: a new material for solar fluorescent planar concentrators?  

NASA Astrophysics Data System (ADS)

Inorganic glasses prepared by the 'cold' chemical sol-gel process can present an alternative host material for organic fluorescent dyes. We report on measurements done on thin Si02 layers prepared as sol-gels and doped with various dyes on a glass substrate. The preparation is done by dip-coating of the substrate in the corresponding alcoxide solutions. Good quality layers without crazing after drying are achieved with a thickness of up to 1-2 microns. The measurements include absorption measurements (UV to IR), fluorescence and excitation measurements (visible to NIR), and measurements of photo-decomposition. The optical properties of the dye molecules in the layer and in the sol-gel solutions are studied as a function of dye concentration and changes in the thermal treatment of the layers. The results are examined for their applicability to FPC's. Further we report on small silver islands (submicron size) brought into the sol-gel solution as stabilized colloids or by chemical reduction of Ag+ salts. According to theoretical predictions, the electromagnetic interaction of silver surface plasmons and dye molecules can result, under certain conditions, in an enhanced fluorescence quantum efficiency and photostability of the dye.

Hinsch, Andreas; Zastrow, Armin

1990-08-01

276

Boehmite filled hybrid sol–gel system as directly writable hard etching mask for pattern transfer  

Microsoft Academic Search

We discuss some preliminary results on the development of a new kind of positive tone resist whose peculiarity is an extreme dry etch resistance. This profitable property is obtained by loading and compatibilizing with ceramic nano particles a radiation sensitive sol–gel silica based hybrid organic\\/inorganic system. With an appropriate choice of the nano particles, the investigated approach is suitable to

Gianluca Grenci; Gioia Della Giustina; Alessandro Pozzato; Giovanna Brusatin; Massimo Tormen

2011-01-01

277

Nonlinear absorption and optical limiting properties in sol-gel solidified gold nanorods  

Microsoft Academic Search

The Optical nonlinearities and optical limiting (OL) properties of Sol-gel solidified gold nanorods were investigated by using Z-scan technique and OL measurement, respectively, with nanosecond pulses at 532nm. The experimental results show that their strong nonlinear optical performances depend on the sizes of nanorods. The surface plasmon absorption is the main mechanism.

Shiliang Qu; Huidan Zeng; Chongjun Zhao; Shiyou Fu; Tianyou Peng; Xiongwei Jiang; Congshan Zhu; Jianrong Qiu

2003-01-01

278

The development and characterization of sol-gel substrates for chemical and optical applications  

Microsoft Academic Search

The sol gel process can be used to make monolithic porous glass for various scientific and engineering uses. The porosity of the material imparts a large surface area which is advantageous in applications such as catalyst supports or in the study of surface mediated chemical reactions. The chemical stability and transparency of the porous glass also make it suitable for

Kevin William Powers

1998-01-01

279

Aluminium Electrodes Effect the Operation of Titanium Oxide Sol-gel Memristors  

Microsoft Academic Search

By a comparison between memristors made with aluminium and gold electrodes, this letter demonstrates that aluminium electrodes are an essential component of the TiO$_2$ sol-gel flexible memristor . Both slow varying `analogue' and sudden switching `digital' memristor devices have been observed. Limiting the oxygen exposure of the bottom aluminium electrode favours the creation of digital memristors over analogue ones. A

Ella Gale; David Pearson; Stephen Kitson; Andrew Adamatzky; Ben de Lacy Costello

2011-01-01

280

Optical materials for surface-enhanced Raman applications based on sol-gel encapsulated gold particles  

Microsoft Academic Search

A photochemical method of producing nanometer gold particles in optically transparent sol-gel silicate materials is described. Organometallic gold precursor compounds are dissolved in the sol and encapsulated in the growing silicate network. Irradiation of the doped monoliths with ultraviolet light causes the photodeposition of gold particles within the silica gel or xerogel. The particles are characterized by their electronic absorption

Fatemeh Akbarian; Bruce S. Dunn; Jeffrey I. Zink

1994-01-01

281

Immobilization of Biomolecules in Sol–Gels: Biological and Analytical Applications  

Microsoft Academic Search

The encapsulation or generation of new surfaces that can fix biomolecules firmly without altering their original conformations and activities is still challenging for the utilization of biochemical functions of active biomolecules. Presently, sol–gel chemistry offers new and interesting possibilities for the promising encapsulation of heat-sensitive and fragile biomolecules (enzyme, protein, antibody and whole cells of plant, animal and microbes); mainly,

Vivek Babu Kandimalla; Vijay Shyam Tripathi; Huangxian Ju

2006-01-01

282

Stress effects in sol-gel derived ferroelectric thin films L. Lian and N. R. Sottosa)  

E-print Network

Stress effects in sol-gel derived ferroelectric thin films L. Lian and N. R. Sottosa) Department 26 August 2003; accepted 19 October 2003 Residual stress development during processing of sol investigates the effects of stress on field-induced polarization switching in ferroelectric Pb Zr0.52Ti0.48)O3

Sottos, Nancy R.

283

Manganese oxide thin films prepared by nonaqueous sol–gel processing: preferential formation of birnessite  

Microsoft Academic Search

High quality manganese oxide thin films with smooth surfaces and even thicknesses have been prepared with a nonaqueous sol–gel process involving reduction of tetraethylammonium permanganate in methanol. Spin-coated films have been cast onto soft glass, quartz, and Ni foil substrates, with two coats being applied for optimum crystallization. The addition of alkali metal cations as dopants results in exclusive formation

Stanton Ching; Steven M. Hughes; Timothy P. Gray; Eric J. Welch

2004-01-01

284

Nanoindentation and adhesion of sol-gel-derived hard coatings on polyester  

E-print Network

Nanoindentation and adhesion of sol-gel-derived hard coatings on polyester C.M. Chan, G.Z. Cao,a) H on the plastic surface. Nanoindentation analysis revealed that the coatings have a surface hardness up to 2.5 ± 0

Cao, Guozhong

285

Tribology of water and oil repellent sol–gel coatings for optical applications  

Microsoft Academic Search

Oil and water repellent sol–gel silica coatings may be used to extend the use and lifetime of certain computer displays, optoelectronic devices, and optical components such as touch screens. Organic–inorganic coatings consisting of organically modified silica are an optimal class of materials to use for such applications as they are substantially more durable than conventional polymers while having low processing

A. J. Kessman; D. K. P. Huckaby; C. R. Snyder; S. N. Kukureka; D. R. Cairns

2009-01-01

286

Preparation of perovskite alumina ceramic membrane using sol–gel method  

Microsoft Academic Search

Perovskite alumina membranes have been synthesized using the sol–gel method. This method involved the peptization of a sol prepared from aluminum secondary-butoxide. The effect of binder on the sol viscosity and crack formation of membrane during drying were studied. It was noted that increasing of binder concentration led to increase sol viscosity. TGA analysis showed that, there is no significant

A. L. Ahmad; N. F. Idrus; M. R. Othman

2005-01-01

287

Preparation of alexandrite by the sol-gel process and its characterisation  

Microsoft Academic Search

Alexandrite is an important material which finds applications in many spheres of science and engineering. It is present in nature as a mineral called “chrysoberyl”. But as its occurrence is limited and impure, this mineral has been produced synthetically to meet various requirements.This paper describes a sol-gel method of preparation of this mineral based on citrate gel processing and identifies

S. Saha; B. P. Mistry

1996-01-01

288

Hybrid Powder-Sol-Gel Ferroelectric Thin Films on Metallic Membranes for Piezoelectric Applications  

Microsoft Academic Search

3 ?m thick lead zirconate titanate films were processed via a hybrid sol-gel-powder method on Inconel substrates for pressure sensor applications. Microstructure, ferroelectric, dielectric and piezoelectric properties are reported. It is shown that crack- free films with good high remnant polarization, and high effective piezoelectric coefficient, d33, could be processed. Sensor membranes were obtained from these film heterostructures, and their

M. Es-Souni; S. Maximov; J. Krause; A. Piorra; G. Stange; C.-H. Solterbeck

2006-01-01

289

Photopatterning of hybrid sol-gel glasses for optical and nonlinear optical applications  

NASA Astrophysics Data System (ADS)

The present paper deals with the development of hybrid sol-gel glasses as host matrixes for molecules having quadratic NLO properties. Second order non-linearities can be observed after poling in order to orient these molecules. However, due to their small size, thermal relaxation processes lead to a decrease of the induced orientation with time. Host matrixes showing a high rigidity and corresponding to a final material presenting a reduced free volume should overcome this drawback. An interesting way is to use the rigidity conferred by an organic-inorganic sol-gel matrix that can polymerize under irradiation. Photopatterning of the layer and simultaneous copolymerization of the hybrid precursor with functionalized chromophores should enhance the second order NLO response. The results presented in this paper focus on the formulation and conditioning of laminated hybrid sol-gel layers with a thickness of 100 ?m that remain crack-free under condensation and photopolymerization. Results are presented concerning the generation of 1 ?m gratings obtained under spatially controlled visible illumination using interference pattern at 514 nm. Diffraction efficiencies up to 90 % are obtained for an incident intensity of 30 mW.cm-2. The next step is now the incorporation of functionalized chromophores in the hybrid sol-gel matrix leading to a study of NLO properties of the final material.

Feuillade, Mathieu; Croutxe-Barghorn, Celine; Mager, Loic; Carre, Christiane P.; Fort, Alain F.

2004-09-01

290

Sol-gel deposition of buffer layers on biaxially textured metal substances  

DOEpatents

A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

Shoup, Shara S. (Woodstock, GA); Paranthamam, Mariappan (Knoxville, TN); Beach, David B. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

2000-01-01

291

Lanthanide nanoparticle doped low-loss sol-gel amplifier materials  

NASA Astrophysics Data System (ADS)

Organic-inorganic hybrid sol-gel materials have attracted increasing attention in recent years as low-cost, rugged materials for integrated optical devices such as optical couplers, splitters, and electro-optic modulators. These materials can be easily processed by spin-coating, wet-etching photolithography, and low-temperature baking. Precise control of waveguide core-cladding refractive indices produces well-confined low-loss propagation and good matching of the absolute refractive index to that of fused silica results in low optical coupling loss to optical fiber. The increased thermal and mechanical stability of these materials, relative to optical polymers, results in numerous packaging options and improved reliability. However organic-inorganic hybrid sol-gel materials have not yet been often used as host of active dopants such as erbium (III) ions for 1550nm optical amplification. This limitation owes primarily to matrix and chelate dominated nonradiative relaxation processes, as high phonon energy OH and OH-like oscillators can bridge off the energy from the excited erbium (III) ions at very high rates. Different strategies have been proposed to protect erbium (III) ions from matrix and chelate quenching, including host and ligand fluorination, and inorganic microstructure shielding. Here we report on our work of encapsulating erbium (III) ions in transparent, refractive index matched, and highly re-dispersible lanthanum phosphate nanoparticles and the work of examining the optical properties of these nanoparticles as active dopants in organic-inorganic hybrid sol-gels adopting 2-methacryloxypropyl trimethoxysilane (MAPTMS) as a precursor. 980nm laser pumped photoluminescence at 1535nm was obtained from solid bulk samples of 300mg La.99Er.01PO4 nanoparticles doped in 1mL hybrid sol-gel. Thick bulk samples of this composition exhibited exceptional clarity and little trace of nanoparticle scattering effects. The lifetime of the nanoparticle doped hybrid sol-gel composite was measured to be 220?s, indicating an intermediate relaxation rate between that of an erbium organic complex and annealed erbium doped glass. La.99Er.01PO4 nanoparticle doped hybrid sol-gel films were also prepared and the refractive index was measured to be 1.4966 at 1550nm, which is very close to that of optical fiber and provides a suitable index difference from an undoped and metal oxide tuned sol-gel at 1.4870 to comprise an efficient single-mode waveguide system.

Gan, Haiyong; Norwood, Robert A.; Li, Li; DeRose, Christopher T.; Wu, Jianfeng; Thomas, Jayan; Fardad, M. Amir; Schuelzgen, Axel; Peyghambarian, Nasser N.; De Silva, Channa R.; Zheng, Zhiping

2005-08-01

292

Conformal sol-gel coatings on three-dimensional nanostructured templates  

NASA Astrophysics Data System (ADS)

Sol-gel processing techniques, such as spin coating and dip coating, have successfully been utilized over the past several decades to apply conformal coatings on planar substrates; however, controlled film growth on three-dimensional (3-D) nanostructured templates using the sol-gel process remains a significant challenge. Obstacles such as, uncontrolled hydrolyzation and condensation of metal alkoxide precursors on nanostructured surfaces are a few of the obstacles which lead to coatings with undesirable thicknesses and excess inorganic particles. A little over a decade ago, a surface sol-gel process was developed which utilizes stepwise film growth of anhydrous metal alkoxide precursors with hydroxylated surfaces. The surface sol-gel process provides control over the applied coating thickness and is viewed as a wet chemical analog to atomic layer deposition (ALD). The work presented in this dissertation has focused on applying conformal sol-gel derived coatings with controlled thicknesses on 3-D nanostructured templates. The templates utilized in this work were derived from biological species, such as diatoms and butterflies, as well as a synthetic photoresist polymer (SU-8). Coatings were applied on the templates using a conventional reflux/evaporation deposition process and a custom-built computer controlled surface sol-gel pumping system. The coatings applied using the reflux/evaporation process yielded conformal coatings with uncontrolled film thicknesses whereas the coatings applied using the surface sol-gel process yielded conformal coatings with controlled thicknesses. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using the reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate-based coatings were obtained on the magnesia frustule replicas possessing uncontrolled thicknesses and excess inorganic particles using the reflux/evaporation deposition process. The europium-doped barium titanate coated frustules exhibited bright red photoluminescent properties upon stimulation with an ultraviolet light source. Silica-based diatom frustules were also utilized as 3-D nanostructured templates for fabrication of a micro-scale nitric oxide gas sensor. Tin oxide coatings were applied on the silica frustules using the automated surface sol-gel pumping system. An organic dendrimer method was developed for amplifying hydroxyl groups on the silica frustule surfaces to enhance the surface sol-gel deposition process. Conformal coatings with controlled thicknesses were obtained on the hydroxyl amplified frustule surfaces; however, little if any deposition was observed on the frustules that were not subjected to the hydroxyl amplification process. A single tin oxide coated diatom frustule served as a gas sensor component which was sensitive to very low concentrations of nitric oxide gas. The automated surface sol-gel system was also used to apply multicomponent tin oxide-doped titania alkoxide chemistries on the wing scales of a blue Morpho butterfly. The alkoxide solutions reacted directly with the OH functionalities provided by the native chitin chemistry of the scales. The tin oxide served as a rutile nucleating agent which allowed the titania to completely crystallize in the high refractive index rutile titania phase with doping concentrations of tin oxide as low as 7 mol% after annealing at 450°C. The tin oxide-doped titania coatings were both nanocrystalline and nanothick and replicated the nanostructured scales with a high degree of accuracy. Undoped titania coatings applied on the scales required a heat treatment of 900°C to crystallize the coating in the rutile titania phase which led to adverse coarsening effects which destroyed the nanostructed features of the scales. Tin oxide-doped titania coatings were also deposited on synthetic polymer (SU-8) pho

Weatherspoon, Michael R.

293

Low temperature and UV curable sol-gel coatings for long lasting optical fiber biosensors  

NASA Astrophysics Data System (ADS)

The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with the analyte can occur within an element of the optical fiber. One of the techniques for this kind of biosensors is to remove the fiber optic cladding and substitute it for biological coatings that will interact with the parameter to sensorize. The deposition of these layers can be made by sol-gel technology. The sol-gel technology is being increasingly used mainly due to the high versatility to tailor their optical features. Incorporation of suitable chemical and biochemical sensing agents have allowed determining pH, gases, and biochemical species, among others. Nonetheless, the relatively high processing temperatures and short lifetime values mean severe drawbacks for a successful exploitation of sol-gel based coated optical fibres. With regard to the latter, herein we present the design, preparation and characterization of novel sol-gel coated optical fibres. Low temperature and UV curable coating formulations were optimized to achieve a good adhesion and optical performance. The UV photopolymerizable formulation was comprised by glycidoxypropyltrimethoxysilane (GLYMO), Tetraethylorthosilicate (TEOS) and an initiator. While the thermoset coating was prepared by using 3-aminopropyltrimethoxysilane, GLYMO, and TEOS as main reagents. Both curable sol-gel coated fibres were analysed by FTIR, SEM and optical characterization. Furthermore, in the present work a new technique for silica cladding removal has been developed by ultra-short pulses laser processing, getting good dimensional accuracy and surface integrity.

Otaduy, D.; Villar, A.; Gomez-Herrero, E.; Goitandia, A. M.; Gorritxategi, E.; Quintana, I.

2010-04-01

294

Magnetic resonance as a structural probe of a uranium (VI) sol-gel process  

SciTech Connect

NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub l2}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sub 17}0 NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, [(UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}]{sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results show that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an ``intercalation`` cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2}[(UO{sub 2}){sub 8}O{sub 4}(OH){sub 10}] {center_dot} 8H{sub 2}0. This compound is the precursor to sintered U0{sub 2} ceramic fuel.

King, C.M.; Thompson, M.C.; Buchanan, B.R. [Westinghouse Savannah River Co., Aiken, SC (United States); King, R.B. [Georgia Univ., Athens, GA (United States). Dept. of Chemistry; Garber, A.R. [South Carolina Univ., Columbia, SC (United States). Dept. of Chemistry

1989-12-31

295

Magnetic resonance as a structural probe of a uranium (VI) sol-gel process  

SciTech Connect

NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub l2}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sub 17}0 NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, ((UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}){sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results show that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2}((UO{sub 2}){sub 8}O{sub 4}(OH){sub 10}) {center dot} 8H{sub 2}0. This compound is the precursor to sintered U0{sub 2} ceramic fuel.

King, C.M.; Thompson, M.C.; Buchanan, B.R. (Westinghouse Savannah River Co., Aiken, SC (United States)); King, R.B. (Georgia Univ., Athens, GA (United States). Dept. of Chemistry); Garber, A.R. (South Carolina Univ., Columbia, SC (United States). Dept. of Chemistry)

1989-01-01

296

Electrical properties of PZT thin films grown by sol–gel and PLD using a seed layer  

Microsoft Academic Search

Lead Zirconate Titanate (PZT) thin films (with molar ratio of Zr:Ti::65\\/35) were deposited by pulsed laser deposition (PLD) and sol–gel technique on Pt\\/Si (111), and Pt\\/Si (100) substrates. A seed layer of PbTiO3 (0.1?m) was coated by sol–gel on the substrates before depositing PZT by PLD and sol–gel. A metal\\/ferroelectric\\/metal (MFM) capacitor structure, formed by depositing gold electrode on top

S. K. Pandey; A. R. James; Chandra Prakash; T. C. Goel; K. Zimik

2004-01-01

297

Electrochemiluminescence detection of NADH and ethanol based on partial sulfonation of sol–gel network with gold nanoparticles  

Microsoft Academic Search

We developed a stable, sensitive electrochemiluminescence (ECL) biosensor based on the synthesis of a new sol–gel material with the ion-exchange capacity sol–gel to coimmobilize the Ru(bpy)32+ and enzyme. The partial sulfonated (3-mercaptopropyl)-trimethoxysilane sol–gel (PSSG) film acted as both an ion exchanger for the immobilization of Ru(bpy)32+ and a matrix to immobilize gold nanoparticles (AuNPs). The AuNPs\\/PSSG\\/Ru(bpy)32+ film modified electrode allowed

Liu Deng; Lihua Zhang; Li Shang; Shaojun Guo; Dan Wen; Fuan Wang; Shaojun Dong

2009-01-01

298

Synthesis and characterization of sol-gel-derived nanomaterials and nanocrystalline electroless metal coatings  

NASA Astrophysics Data System (ADS)

CuS (minimum size of 2.5 nm), Ag2S (minimum and average size of 2.5 nm and 26 nm respectively), and Au (with minimum size of <10 nm) nanoparticles dispersed within the sol-gel derived hydroxypropyl cellulose (HPC)-silica films are synthesized using the gas diffusion technique. The effectiveness of HPC polymer, as a 'compatibilizer', to synthesize semiconductor and metal nanoparticles distributed uniformly within the silica film is demonstrated. The sol-gel derived HPC-silica films containing dispersed nanoparticles are characterized using x-ray photoelectron spectroscopy (XPS) to understand the mechanism of formation of nanoparticles within the film. The XPS core-level binding energies (B.E.) for the nanoparticles are observed to be sensitive to the variation in the chemical composition at the surface and their size. The 'cluster size effect' is shown to be useful in predicting the average nanoparticle size. Nanocrystalline ZrO2 particles are successfully synthesized using sol-gel technique utilizing HPC polymer as a 'steric barrier'. The use of HPC polymer is demonstrated to synthesize submicron-sized, non-agglomerated, and spherical as well as nanocrystalline ZrO2 particles by adjusting the sol-gel synthesis parameters. The effect of sol-gel synthesis parameters on ZrO2 nanocrystallite size, its distribution, and the phase evolution behavior of ZrO2 is studied. The optimum sol-gel synthesis parameters for synthesizing nanocrystalline ZrO2 with 100% tetragonal phase are identified. Cu/CuO-ZrO2 composite powder is synthesized using the electroless metal deposition technique. The mechanism of electroless deposition of Cu over ZrO2 particle surface is investigated using XPS. On the basis of 'cluster size effect', it is suggested that, the electroless metal deposition process activates the non-catalytic ceramic substrate surface by depositing metallic Pd0 clusters and not by the accepted Pd-Sn alloy catalyst. Fly ash cenosphere particle surface is also activated by metallic Pd0 clusters under similar coating conditions. The cenosphere particles are further coated with Ag using Pd-activation. The Cu and Ag-coated cenosphere particles find application in manufacturing conducting polymers used for electromagnetic interference (EMI) shielding application. The use of cost-effective activator (AgNO3) is demonstrated for coating the cenosphere particles with Cu for commercialization. The use of Focussed Ion Beam (FIB) microscopy technique is demonstrated to directly measure the coating-thickness.

Shukla, Satyajit Vishnu

299

Non-aqueous electrolyte solutions  

NASA Astrophysics Data System (ADS)

Non-aqueous electrolyte solutions are nowadays intensively studied owing to their unique properties for their application in various electrochemical devices and procedures. Important advances have already been made in high-energy primary batteries, wet capacitors, electroplating, phase-transfer catalysis and electro-organic synthesis; advances are expected in further fields such as high-energy secondary batteries, non-emissive displays, solar cells, thin-film procedures and coating. A survey is given both for successful recent applications and expectations.

Gores, H.-J.; Barthel, J.

1983-10-01

300

Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior  

SciTech Connect

Highlights: ? New sol–gel routes to replace chromates for corrosion protection of aluminum. ? Effect of cerium concentration on the microstructure of xerogel. ? Electrochemical and mechanical performances of hybrid coating with different cerium contents. ? Good correlation between the different results with an optimal cerium content of 0.01 M. -- Abstract: An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(O{sup s}Bu){sub 3}, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating.

Cambon, Jean-Baptiste, E-mail: cambon@chimie.ups-tlse.fr [Institut Carnot CIRIMAT, Université de Toulouse, UMR CNRS 5085, 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France)] [Institut Carnot CIRIMAT, Université de Toulouse, UMR CNRS 5085, 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France); Esteban, Julien; Ansart, Florence; Bonino, Jean-Pierre; Turq, Viviane [Institut Carnot CIRIMAT, Université de Toulouse, UMR CNRS 5085, 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France)] [Institut Carnot CIRIMAT, Université de Toulouse, UMR CNRS 5085, 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France); Santagneli, S.H.; Santilli, C.V.; Pulcinelli, S.H. [Departamento F?sico-Química, Instituto de Química, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil)] [Departamento F?sico-Química, Instituto de Química, Universidade Estadual Paulista, UNESP, CP 355, 14801-970 Araraquara, SP (Brazil)

2012-11-15

301

Sol-gel preparation and characterization of SiO2 coated VO2 films with enhanced transmittance and high thermochromic performance  

NASA Astrophysics Data System (ADS)

Vanadium dioxide (VO2) films prepared at low-temperature with a low cost are considerable for energy-saving applications. Here, SiO2 coated VO2 films with clearly enhanced visible transmittance by introducing antireflection coatings (ARCs) and excellent thermochromic performance were present. The VO2 films have been prepared via a stable and low-cost sol-gel synthesis route using vanadium pentaoxide powder as precursor, and their structural, morphological, optical and electrical properties and thermochromic performance were systemically characterized. The resistance of VO2 films varies by 4 orders of magnitude and the transmittance changes from 11.8% to 69.3% at 2500 nm while no significant deviation appears in the visible region during metal-insulator transition (MIT). Nanoporous SiO2 coating with good optical transparency was coated on the surface of VO2 film via sol-gel dip-coating technique to enhance its optical transmittance, and the visible transmittance is increased by 14.6% due to the significantly decreased reflectance. The critical transition temperature (63 °C) and infrared switching properties of VO2 films are not much deteriorated by applying SiO2 layer. The synergistic effect of antireflection and thermochromism on SiO2 coated VO2 films was investigated.

Li, Dezeng; Shan, Yongkui; Huang, Fuqiang; Ding, Shangjun

2014-10-01

302

Photoresist-free fully self-patterned transparent amorphous oxide thin-film transistors obtained by sol-gel process.  

PubMed

We demonstrated self-patterned solution-processed amorphous oxide semiconductor thin-film transistors (TFTs) using photosensitive sol-gels. The photosensitive sol-gels were synthesized by adding ?-diketone compounds, i.e., benzoylacetone and acetylacetone, to sol-gels. The chemically modified photosensitive sol-gels showed a high optical absorption at specific wavelengths due to the formation of metal chelate bonds. Photoreactions of the modified solutions enabled a photoresist-free process. Moreover, Zn-Sn-O with a high Sn ratio, which is hard to wet-etch using conventional photolithography due to its chemical durability, was easily patterned via the self-patterning process. Finally, we fabricated a solution-processed oxide TFT that included fully self-patterned electrodes and an active layer. PMID:24686314

Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

2014-01-01

303

Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process  

PubMed Central

We demonstrated self-patterned solution-processed amorphous oxide semiconductor thin-film transistors (TFTs) using photosensitive sol-gels. The photosensitive sol-gels were synthesized by adding ?-diketone compounds, i.e., benzoylacetone and acetylacetone, to sol-gels. The chemically modified photosensitive sol-gels showed a high optical absorption at specific wavelengths due to the formation of metal chelate bonds. Photoreactions of the modified solutions enabled a photoresist-free process. Moreover, Zn–Sn–O with a high Sn ratio, which is hard to wet-etch using conventional photolithography due to its chemical durability, was easily patterned via the self-patterning process. Finally, we fabricated a solution-processed oxide TFT that included fully self-patterned electrodes and an active layer. PMID:24686314

Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

2014-01-01

304

Sol-gel nanocasting synthesis of patterned hierarchical LaFeO3 fibers with enhanced catalytic CO oxidation activity  

NASA Astrophysics Data System (ADS)

Hierarchical LaFeO3 fibers were prepared by a sol-gel nanocasting method using a cotton cloth as the template. The resulting LaFeO3 fibers inherited the initial network morphology of the template very well and showed enhanced catalytic CO oxidation activity and satisfactory stability compared to the counterpart particles prepared by the conventional sol-gel method.Hierarchical LaFeO3 fibers were prepared by a sol-gel nanocasting method using a cotton cloth as the template. The resulting LaFeO3 fibers inherited the initial network morphology of the template very well and showed enhanced catalytic CO oxidation activity and satisfactory stability compared to the counterpart particles prepared by the conventional sol-gel method. Electronic supplementary information (ESI) available: Materials, detailed experimental procedures and characterization, XRD patterns, SEM and TEM images, BET data and XPS spectra. See DOI: 10.1039/c0nr00760a

Li, Pengna; Hu, Xianluo; Zhang, Lei; Dai, Hongxing; Zhang, Lizhi

2011-03-01

305

Regioselective hydroaminomethylation of vinylarenes by a sol-gel immobilized rhodium catalyst.  

PubMed

In the course of our studies toward the development of new heterogeneous conditions for better controlling regioselectivity in organic reactions, we investigated the application of sol-gel immobilized organometallic catalyst for regioselective hydroaminomethylation of vinylarenes with aniline or nitroarene derivatives in an aqueous microemulsion. By immobilization of 6 mol % [Rh(cod)Cl]2 within a hydrophobic silica sol-gel matrix we were able to perform efficient hydroaminomethylation under mild conditions and isolate 2-arylpropylamines with high regioselectivity. The regioselectivity of the reaction was found to be mainly dependent on the hydrophobicity of the catalyst support. It is also significantly affected by the electronic nature of the substrates, by the reaction temperature, and by syngas pressure. The heterogenized catalyst can be reused for several times. PMID:24528141

Nairoukh, Zackaria; Blum, Jochanan

2014-03-21

306

Spectroscopic properties of pure and Coumarin 153-doped thin films of sol-gel silica xerogels  

NASA Astrophysics Data System (ADS)

Thin-films doped with Coumarin 153, an important laser dye, have been prepared by the sol-gel method. Spectroscopic properties of the entrapped dye are studied by electronic absorption, diffuse reflectance, electronic excitation, emission and time-resolved emission techniques. The obtained results indicate that the entrapment of the dye results in formation of molecular aggregates having absorption and emission characteristics different from those of the monomeric dye. The blue matrix emission band (at approx. 450 nm) is relatively short-lived while the red band (at approx. 700 nm) displays a very long lifetime. Electronic excitation spectra of the sol-gel thin-films suggest that the two matrix-related luminescence bands possess the same electronic origin.

Maruszewski, K.

1999-04-01

307

The porosity of sol-gel silica thin films for optrode applications  

SciTech Connect

Porous silica thin films produced by sol-gel processing are being considered for use in optical sensor (optrode) applications. In this study, thin films were produced by dip-coating onto glass slides. The porosity was then measured indirectly, by determining the amount of methylene blue adsorption on each slide. Using this technique, it has been determined that the {open_quotes}two-step{close_quotes} sol-gel process provides a greater surface area than the acid-catalyzed process. With the two-step process, increasing the amount of solvent (ethanol) and decreasing the rate of slide withdrawal from the sol provided increased surface area when normalized to the mass of the deposit.

Harris, T.M.; Knobbe, E.T. [Oklahoma State Univ., OK (United States)

1995-12-01

308

Amperometric glucose biosensor based on sol-gel organic-inorganic hybrid material.  

PubMed

A new type of sol-gel organic-inorganic hybrid material was developed and used for the production of biosensors. This material is composed of silica sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. It prevents the cracking of conventional sol-gel-derived glasses and eliminates the swelling of the hydrogel. The optimum composition of the hybrid material was first examined, and then glucose oxidase was immobilized in this matrix to demonstrate its application. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (600 nA mmol-1 L-1), short response time (11 s) and remarkable long-term stability in storage (at least 5 months). In addition, the characteristics of the second-generation biosensor with the use of tetrathiafulvalene as a mediator were discussed. PMID:11013720

Wang, B; Li, B; Deng, Q; Dong, S

1998-08-01

309

Whole Cell Imprinting in Sol-Gel Thin Films for Bacterial Recognition in Liquids: Macromolecular Fingerprinting  

PubMed Central

Thin films of organically modified silica (ORMOSILS) produced by a sol-gel method were imprinted with whole cells of a variety of microorganisms in order to develop an easy and specific probe to concentrate and specifically identify these microorganisms in liquids (e.g., water). Microorganisms with various morphology and outer surface components were imprinted into thin sol-gel films. Adsorption of target microorganism onto imprinted films was facilitated by these macromolecular fingerprints as revealed by various microscopical examinations (SEM, AFM, HSEM and CLSM). The imprinted films showed high selectivity toward each of test microorganisms with high adsorption affinity making them excellent candidates for rapid detection of microorganisms from liquids. PMID:20480018

Cohen, Tally; Starosvetsky, Jeanna; Cheruti, Uta; Armon, Robert

2010-01-01

310

Reversible sol-gel transition of oligo(p-phenylenevinylene)s by ?-? stacking and dissociation.  

PubMed

Methyl sulfide terminated trans-oligo(p-phenylenevinylene) derivatives (OPVn, n is the number of phenyl rings) were synthesized, and reversible sol-gel transition was observed in a variety of organic solvents. Investigations with UV-vis, fluorescence, and (1)H NMR spectroscopy revealed that aromatic ?-? stacking and van der Waals forces were important in the formation of the gels, with the former being the main driving force for sol-gel transition. The ?-conjugation length showed a key influence on self-assembly and gelation property: the gel-to-sol transition temperature (Tgel) increased with ?-conjugation length. The gels of OPV4-7 can self-assemble into one-dimensional fibers with different sizes and shapes, depending on their ?-conjugation length. On the basis of X-ray diffraction measurements and spectroscopic data, a self-assembly model was proposed. Our observation may be useful for designing functional ?-gelators based on ?-? stacking. PMID:24702243

Yao, Chuan; Lu, Qi; Wang, Xianhong; Wang, Fosong

2014-05-01

311

Reversible Sol-Gel Transitions in Aqueous Solutions of N-Isopropylacrylamide Ionic Copolymers  

SciTech Connect

Ionic copolymers of N-isopropylacrylamide (NIPA) exhibiting sol-gel transitions in aqueous solutions were investigated. The studies were aimed at understanding of the structure-property relationship in design of injectable, in situ forming gels for potential biomedical applications in delivery of therapeutics and tissue engineering. Aqueous solutions of NIPA ionic copolymers were found to flow freely at ambient temperatures and formed soft gels with controlled syneresis above 32°C, the lower critical solution temperature of NIPA. The sol-gel transitions and temperature dependent properties of the resulting gels were analyzed using dynamic rheometry, UV and IR spectrometry, and were found to be controlled by the molecular weight and composition of copolymers, ionization state of comonomers, and composition of aqueous solvent.

Krzyminski, Karol J.; Jasionowski, Marek; Gutowska, Anna

2008-04-01

312

Transparent ultralow-density silica aerogels prepared by a two-step sol-gel process  

SciTech Connect

Conventional silica sol-gel chemistry is limited for the production of transparent ultralow-density aerogels because (1) gelation is either slow or unachievable, and (2) even when gelation is achieved, the large pore sizes result in loss of transparency for aerogels <.020 g/cc. We have developed a two-step sol-gel process that circumvents the limitations of the conventional process and allows the formation of ultralow-density gels in a matter of hours. we have found that the gel time is dependent on the catalyst concentration. After supercritical extraction, the aerogels are transparent, uncracked tiles with densities as low as .003 g/cc. 6 figs., 11 refs.

Tillotson, T.M.; Hrubesh, L.W.

1991-09-01

313

Electron exchange columns through entrapment of a nickel cyclam in a sol-gel matrix.  

PubMed

An electron exchange column (analogous to ion exchange columns) was developed using the unique redox properties of the nickel-tetraazamacrocyclic complexes (nickel cyclam [Ni(II)L(1)](2+)) and nickel-trans-III-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, ([Ni(II)L(2)](2+)), and the physical and chemical stability of the ceramic materials using the sol-gel process to entrap the complexes. The entrapment by the biphasic sol-gel method is based on non-covalent bonds between the matrix and the complex; therefore the main problem was leaching. Parameters controlling the leaching were investigated. Redox cycles with the reducing agent ascorbic acid, and persulfate as the oxidizing agent were performed. PMID:21465586

Lavi, Yair; Burg, Ariela; Maimon, Eric; Meyerstein, Dan

2011-04-26

314

Relaxation dynamics near the sol-gel transition: From cluster approach to mode-coupling theory  

NASA Astrophysics Data System (ADS)

A long standing problem in glassy dynamics is the geometrical interpretation of clusters and the role they play in the observed scaling laws. In this context, the mode-coupling theory (MCT) of type-A transition and the sol-gel transition are both characterized by a structural arrest to a disordered state in which the long-time limit of the correlator continuously approaches zero at the transition point. In this paper, we describe a cluster approach to the sol-gel transition and explore its predictions, including universal scaling laws and a new stretched relaxation regime close to criticality. We show that while MCT consistently describes gelation at mean-field level, the percolation approach elucidates the geometrical character underlying MCT scaling laws.

Coniglio, A.; Arenzon, J. J.; Fierro, A.; Sellitto, M.

2014-10-01

315

Sol-gel solution-deposited InGaZnO thin film transistors.  

PubMed

Thin film transistors (TFTs) fabricated by solution processing of sol-gel oxide semiconductor precursors in the group In-Ga-Zn are described. The TFT mobility varies over a wide range depending on the precursor materials, the composition, and the processing variables, with the highest mobility being about 30 cm(2)/(V s) for IZO and 20 cm(2)/(V s) for IGZO. The positive dark bias stress effect decreases markedly as the mobility increases and the high mobility devices are quite stable. The negative bias illumination stress effect is also weaker in the higher mobility TFTs, and some different characteristic properties are observed. The TFT mobility, threshold voltage, and bias stress properties are discussed in terms of the formation of self-compensated donor and acceptor states, based on the chemistry and thermodynamics of the sol-gel process. PMID:24593772

Street, Robert A; Ng, Tse Nga; Lujan, René A; Son, Inyoung; Smith, Matthew; Kim, Sangbok; Lee, Taegweon; Moon, Yongsik; Cho, Sungseo

2014-03-26

316

Sol gel based fiber optic sensor for blook pH measurement  

SciTech Connect

This paper describes a fiber-optic pH sensor based upon sol-gel encapsulation of a self-referencing dye, seminaphthorhodamine-1 carboxylate (SNARF-1C). The simple sol-gel fabrication procedure and low coating leachability are ideal for encapsulation and immobilization of dye molecules onto the end of an optical fiber. A miniature bench-top fluorimeter system was developed for use with the optical fiber to obtain pH measurements. Linear and reproducible responses were obtained in human blood in the pH range 6.8 to 8.0, which encompasses the clinically-relevant range. Therefore, this sensor can be considered for in vivo use.

Grant, S. A.; Glass, R. S.

1996-12-19

317

Nanocrystalline indium tin oxide fabricated via sol-gel combustion for electrochemical luminescence cells.  

PubMed

Nanoporous indium tin oxide (ITO) was synthesized via a sol-gel combustion hybrid method using Ketjenblack as a fuel. The effects of the sol-gel combustion conditions on the structures and morphology of the ITO particles were studied. The size of the nanoporous powder was found to be 20-30 nm in diameter. The layer of the nanoporous ITO electrode (-10 microm thickness) with large surface area (-360 m2/g) was fabricated for an electrochemical luminescence (ECL) cell. At 4 V bias, the ECL efficiency of the cell consisting of the nanoporous ITO layer was approximately 1050 cd/m2, which is significantly higher than the cell using only the FTO electrode (450 cd/m2). The nanoporous ITO layer was effective in increasing the ECL intensities. PMID:22849163

Chaoumead, Accarat; Kim, Tae-Woo; Park, Min-Woo; Sung, Youl-Moon

2012-04-01

318

Sol-gel coatings for high power laser optics-past, present and future  

SciTech Connect

An investigation into the preparation of sol-gel coatings for high power lasers was started at LLNL in 1983 and AR coatings were successfully developed for use in the Nova laser in 1984. Several other large lasers now use these coatings. Subsequent work on HR coatings resulted in AlOOH/SiO{sub 2} and later ZrO{sub 2} or HfO{sub 2}/SiO{sub 2} systems of good optical performance. The use of organic polymer binders gave increased damage threshold and enhanced optical performance. We are in the process of scaling up HR fabrication for substrates approximately 38 cm square. Concurrently we are developing sol-gel random phase plates for laser beam smoothing. These have a patterned surface design of silica which induces phase shifts in the beam by variation in the optical path length. Plates of this type on 80 cm diameter substrates have been used successfully on the Nova.

Thomas, I.M.

1993-12-21

319

Ultrapure glass optical waveguide development in microgravity by the sol-gel process  

NASA Technical Reports Server (NTRS)

Containerless melting of glasses in space for the preparation of ultrapure homogeneous glass for optical waveguides is discussed. The homogenization of the glass using conventional raw materials is normally achieved on Earth either by the gravity induced convection currents or by the mechanical stirring of the melt. Because of the absence of gravity induced convection currents, the homogenization of glass using convectional raw materials is difficult in the space environment. Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation.

1982-01-01

320

Cooperative energy transfer in Yb3+–Tb3+ codoped silica sol-gel glasses  

Microsoft Academic Search

Optical properties of Yb3+–Tb3+ codoped silica sol-gel samples have been studied after the gel to glass transition. Different upconversion emissions have been observed under near infrared excitation at about 1 ?m. The Tb3+ ions are excited by means of energy transfer processes from Yb3+ ions. The temporal evolution of the blue-green upconversion emissions coming from Tb3+ ions and their dependence

I. R. Mart?´n; A. C. Yanes; J. Me´ndez-Ramos; M. E. Torres; V. D. Rodr?´guez

2001-01-01

321

Photoluminescence behavior of poly(quinoline)s in silica glasses via the sol-gel process  

Microsoft Academic Search

A full color display with its spectra covering the entire visible color range using a single polymer is presented here. Different concentrations of poly(2,6-[4-phenylquinoline]) and poly(2,6-[p-phenylene]-4-phenylquinoline) were incorporated into silica gels via the sol-gel technique. At high concentrations, the conjugated polymers form multiple excimers in the channels within the silica network, leading to the emission of red light (~600 nm).

W. Y. Huang; S. W. Ho; T. K. Kwei; Y. Okamoto

2002-01-01

322

Cooperative energy transfer in Yb3+Tb3+ codoped silica sol-gel glasses  

Microsoft Academic Search

Optical properties of Yb3+-Tb3+ codoped silica sol-gel samples have been studied after the gel to glass transition. Different upconversion emissions have been observed under near infrared excitation at about 1 mum. The Tb3+ ions are excited by means of energy transfer processes from Yb3+ ions. The temporal evolution of the blue-green upconversion emissions coming from Tb3+ ions and their dependence

I. R. Martín; A. C. Yanes; J. Méndez-Ramos; M. E. Torres; V. D. Rodríguez

2001-01-01

323

Photoluminescence behavior of poly(quinoline)s in silica glasses via the sol–gel process  

Microsoft Academic Search

A full color display with its spectra covering the entire visible color range using a single polymer is presented here. Different concentrations of poly(2,6-[4-phenylquinoline]) and poly(2,6-[p-phenylene]-4-phenylquinoline) were incorporated into silica gels via the sol–gel technique. At high concentrations, the conjugated polymers form multiple excimers in the channels within the silica network, leading to the emission of red light (?600 nm).

W. Y. Huang; S. W. Ho; T. K. Kwei; Y. Okamoto

2002-01-01

324

A low cost fiber-optic humidity sensor based on silica sol–gel film  

Microsoft Academic Search

A highly sensitive low cost fiber-optic humidity sensor based on evanescent wave scattering and evanescent wave absorption has been developed. The sensor is fabricated using a U-bend optical fiber which is coated with silica film using sol–gel process and doped with Methylene Blue. We investigated the sensing property of the sensor in different aspects and found that the normalized absorbance

Zhongjun Zhao; Yixiang Duan

325

Incoherent scattering near a sol gel transition P. G. de Gennes  

E-print Network

Incoherent scattering near a sol gel transition P. G. de Gennes Collège de France, 75231 Paris de self corrélation de van Hove pour un monomère marqué dans un sys- tème en cours de gélation. L exposants critiques de la fraction gel, de la longueur de corrélation, et de la visco- sité macroscopique. 2

Boyer, Edmond

326

Optical sol-gel coatings : ellipsometry of film formation Alan J. Hurd and C. Jeffrey Brinker  

E-print Network

. France 49 (1988) 1017-1025 JUIN 1988, Classification Physics Abstracts 07.60F - 68.15 - 81.15L - 82.70G 11017 Optical sol-gel coatings : ellipsometry of film formation Alan J. Hurd and C. Jeffrey Brinker ; cette méthode donne l'épaisseur du film et son indice de réfraction en fonction de la position. Les

Boyer, Edmond

327

Physical properties of natively textured yttrium doped zinc oxide films by sol-gel  

Microsoft Academic Search

Sol-gel derived yttrium doped ZnO films of various thicknesses have been deposited by the dip coating technique. The investigations of microstructural, electrical and optical properties of post heat-treated films in air as a function of thickness have been made. It is found that high quality films are obtained at an annealing temperature of 550 ?C. The (002) preferential growth of

R. Kaur; A. V. Singh; R. M. Mehra

2005-01-01

328

Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating  

Microsoft Academic Search

The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0~5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

M. H. Mamat; A. S. Rodzi; M. Rusop

2011-01-01

329

Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating  

Microsoft Academic Search

The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0?5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

M. H. Mamat; A. S. Rodzi; M. Rusop

2011-01-01

330

Optical, electrical and structural properties of sol gel ZnO:Al coatings  

Microsoft Academic Search

Single and multilayer transparent conducting aluminium doped zinc oxide films have been prepared on DESAG AF45 substrates by the sol gel dip coating process. Zinc acetate solutions of 0.1–0.5 M in isopropanol stabilised by diethanolamine and doped with a concentrated solution of aluminium nitrate in ethanol were used. Each layer was fired at 600°C in a conventional furnace for 15

T. Schuler; M. A Aegerter

1999-01-01

331

Nanomechanical and Dielectric Properties of Sol-Gel Derived PZT Thin Films Annealed with Microwave Energy  

Microsoft Academic Search

Lead zirconium titanate Pb (Zr0.58Ti0.42) O3 (PZT) thin films were deposited on silicon substrates by sol-gel process. The structural, morphological, dielectric and nano mechanical properties of these films have been studied systematically. The thicknesses of the films were around 160 nm. During the deposition of each layer, the films were baked in a microwave oven which in turn resulted in

A. Rambabu; K. Sudheendran; K. C. James Raju

2010-01-01

332

Preparation of delafossite-type CuCrO 2 films by sol–gel method  

Microsoft Academic Search

High-quality c-axis oriented delafossite-type CuCrO2 films were successfully prepared by a simple sol–gel method. The microstructure, optical properties as well as room temperature resistivity were studied. It was found that the grain sizes of CuCrO2 films pretreated with different temperatures are different; the films were smooth and consisted of fine particles. The maximal transmittance of CuCrO2 films can reach 70%

Jinmei Wang; Peichao Zheng; Da Li; Zanhong Deng; Weiwei Dong; Ruhua Tao; Xiaodong Fang

2011-01-01

333

X-ray reflectivity of zirconia based sol–gel coatings on borosilicate glasses  

Microsoft Academic Search

In this work the technique of X-ray reflectometry was applied to study zirconiumsulfate films deposited by sol–gel dip-coating process on a borosilicate glass surface. The influence of withdrawal speed and temperature of thermal treatment on the film structure are analyzed. The thermal evolution of the density and thickness of the film was compared with these properties measured for a monolithic

A. P. Rizzato; C. V. Santilli; S. H. Pulcinelli

1999-01-01

334

Investigation on sol–gel synthesized Ag-doped TiO 2 cermet thin films  

Microsoft Academic Search

Undoped TiO2 and Ag–TiO2 (up to 23 at.% Ag) cermet thin films and polycrystalline powders have been prepared by sol–gel process. Their structure, composition, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultraviolet–visible spectroscopy (UV–VIS spectroscopy). It has

Suchitra Sen; S. Mahanty; S. Roy; O. Heintz; S. Bourgeois; D. Chaumont

2005-01-01

335

Preparation and characterization of sol–gel derived silver-silica nanocomposite  

Microsoft Academic Search

Composite silver silicate nano-particles were prepared by sol–gel method to investigate the effect of annealing temperature and time durations. The prepared samples were subjected to heat treatment in the temperature range 100–350°C for different time durations. Characterization of heat treated samples was carried out by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), (UV–vis–NIR) spectroscopy and scanning electron microscopy

Surender Duhan; N. Kishore; P. Aghamkar; Sunita Devi

2010-01-01

336

Formation of copper and silver nanometer dimension clusters in silica by the sol-gel process  

Microsoft Academic Search

Ag and Cu (pure and\\/or mixture) nanoclusters doped silica films were prepared by the sol-gel process. In the case of Ag and Cu codoped silica films, Cu\\/Ag molar ratio was 1, 2, and 3 at constant (Ag+Cu)\\/SiO2 molar ratio of 0.175. Separated Ag and Cu nanoclusters are formed in the silica matrix. The size of the clusters and their distribution

G. de; L. Tapfer; M. Catalano; G. Battaglin; F. Caccavale; F. Gonella; P. Mazzoldi; R. F. Haglund Jr.

1996-01-01

337

Synthesis of chalcones catalyzed by aminopropylated silica sol–gel under solvent-free conditions  

Microsoft Academic Search

Aminopropylated nanosilica was prepared by a simple sol–gel process from tetraethyl orthosilicate (TEOS) and then it was functionalized with different amounts of 3-aminopropyltriethoxysilane (APS) under toluene reflux. The prepared solids were characterized by means of XRD, FT-IR, TGA–DTA, SEM–EDS, and TEM. Their textural properties were determined by adsorption–desorption isotherms of N2 at 77K. It was proved that the amount of

Gustavo Romanelli; Gustavo Pasquale; Ángel Sathicq; Horacio Thomas; Juan Autino; Patricia Vázquez

2011-01-01

338

Synthesis and photocatalytic characterization of titania-supported bamboo charcoals by using sol–gel method  

Microsoft Academic Search

The present work examined the photocatalytic behavior of methylene blue (MB) on titania-dispersed bamboo charcoals, prepared by sol–gel method combined with chemical-wet impregnation. The experimental results of nitrogen adsorption showed that specific surface area of the TiO2-charcoals was found to increase with TiO2 loading, whereas their mean pore sizes exhibited a decreasing trend. It can be suggested that TiO2 nanoparticles

Chi-Hsin Wu; Jin-Fang Shr; Chu-Fu Wu; Chien-Te Hsieh

2008-01-01

339

Sol–gel-entrapped nano silver catalysts-correlation between active silver species and catalytic behavior  

Microsoft Academic Search

Silver colloids prepared by reducing AgNO3 in aqueous solution with sodium citrate were embedded in alumina following two different preparation procedures resulting in samples containing 3 and 5wt.% silver. Characterization of these materials using TEM, XPS, XAES, CP\\/MAS NMR, XRD, and adsorption–desorption isotherms of nitrogen showed that embedding the pre-prepared silver colloids into the alumina via the sol–gel procedure preserved

Vasile I. Pârvulescu; Bogdan Cojocaru; Viorica Pârvulescu; Ryan Richards; Zhi Li; Chris Cadigan; Pascal Granger; Pierre Miquel; Chris Hardacre

2010-01-01

340

Preparation of titanium(IV) oxide thin film photocatalyst by sol–gel dip coating  

Microsoft Academic Search

Thin films of titanium dioxide (TiO2) were deposited on variety of substrates by a simple sol–gel dip coating technique. The substrates were coated with titanium peroxide precursor solution of controlled viscosity at a constant pulling rate of 1mms?1, air-dried and further heated at 400°C to obtain uniform films with good adhesion to the substrate. The change in viscosity of the

R. S Sonawane; S. G Hegde; M. K Dongare

2003-01-01

341

Sol-Gel Processing of Zirconia Coating for HR Mirrors with High Laser Damage Threshold  

Microsoft Academic Search

High laser-damage resistant coatings are very important in high power laser systems. In this study ZrO2 thin films are prepared by sol-gel spin-coating technology from suitable zirconia aqueous colloidal suspensions containing nano-crystalline ZrO2 at room temperature synthesized by a hydrothermal process from an inorganic precursor (ZrOCl2·8H2O). By adding a soluble organic binder PVP to the suspension prior to application, it

Jun Shen; Qinyuan Zhang; Jue Wang; Tianhe Yang; Zhongsheng Deng; Bin Zhou; Linyan Chen

2000-01-01

342

Influence of some physical parameters on sol-gel-derived TiO2 thin films  

Microsoft Academic Search

We present some physical parameters that affect the deposition of TiO2 films by the sol-gel method. A set of solutions with different TiO2 concentrations has been prepared. After synthesis of a set of TiO2 films by spin coating at different spinning speeds, the films were annealed at different temperatures. The viscosities of the start solutions were measured by a viscometer.

S. M. Attia; Jue Wang; Jun Shen; Guangming Wu; Qinyuan Zhang; Zhenquan Lai; Tianhe Yang

2000-01-01

343

Study of the influence of some DCCAs on the structure of sol–gel silica membranes  

Microsoft Academic Search

We obtained silica gel membranes by sol–gel processing. In order to study the effect of some drying control chemical additives, we used an alkoxide\\/additive molar ratio of 1\\/1. The performance of the drying additives in obtaining crack-free gels was evaluated through monolithicity measurements. The structural evolution occurring in the interconnected network of the membranes during thermal treatment was monitored by

Rúbia F. S. Lenza; Wander L. Vasconcelos

2003-01-01

344

Effect of glycerol on the optical and physical properties of sol–gel glass matrices  

Microsoft Academic Search

Glass samples are prepared with different amount of glycerol as drying control chemical additive (DCCA) via acid catalysed\\u000a sol–gel method. These samples are given solvent treatment namely rinse and dip with methanol while drying of the sample. In\\u000a rinse treatment solid sample is rinsed with small amount of methanol while in dip treatment sample is dipped for 5 h in methanol.

Aparna V. Deshpande; Jayraj R. Rane; Laxman V. Jathar

2009-01-01

345

Chemical effects of DCCA to the sol-gel reaction process  

Microsoft Academic Search

The effects of drying control chemical additives (DCCA) on the growth of silica particles, gelation time and physical properties of the dry gel were examined in a two-step silica sol-gel process.N,N-dimethylformamide,N,N-dimethylacetamide and ethylene glycol (EG) were applied as DCCAs. The shapes of growing silica particles were distorted spheres on addition of DCCA. EG accelerated the gelation process. Despite the use

N. Uchida; N. Ishiyama; Z. Kato; K. Uematsu

1994-01-01

346

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method  

Microsoft Academic Search

Hydroxyapatite (HA) was coated onto a titanium (Ti) substrate with the insertion of a titania (TiO2) buffer layer by the sol–gel method. The HA layer was employed to enhance the bioactivity and osteoconductivity of the Ti substrate, and the TiO2 buffer layer was inserted to improve the bonding strength between the HA layer and Ti substrate, as well as to

Hae-Won Kim; Young-Hag Koh; Long-Hao Li; Sook Lee; Hyoun-Ee Kim

2004-01-01

347

Soft tissue attachment on sol–gel-treated titanium implants in vivo  

Microsoft Academic Search

This study was designed to examine the attachment and reactions of soft tissues to sol–gel-derived TiO2 coatings. In the first experiment, TiO2 coated and uncoated titanium cylinders were placed subcutaneously into the backs of rats for 3, 11 and 90 days. Tissue response\\u000a and implant surfaces were characterized with routine light microscopy and scanning electron microscopic (SEM) analysis. In\\u000a the second

H. Paldan; S. Areva; T. Tirri; T. Peltola; T. C. Lindholm; L. Lassila; L. J. Pelliniemi; R.-P. Happonen; T. O. Närhi

2008-01-01

348

Formation of superhydrophobic boehmite film on glass substrate by sol-gel method  

Microsoft Academic Search

Superhydrophobic boehmite film has been successfully prepared on a glass substrate by a sol-gel method. A chelated Aluminum-sec-butoxide\\u000a (Al(OBus)3) solution, instead of aluminum hydroxide collosol, was used for the film coating. By immersing the film in boiling water,\\u000a boehmite crystal was formed on a glass substrate. Subsequently, the rough surface was modified with fluoroalkylsilane (FAS).\\u000a The result shows that the

Xinhui Fang; Zhijia Yu; Xiangyu Sun; Xinhua Liu; Futao Qin

2009-01-01

349

Bleaching of sol-gel glass film with embedded gold nanoparticles by thermal poling  

Microsoft Academic Search

Gold clusters embedded in glass are expected to be hard to dissolve in the form of ions since gold is essentially a nonreactive metal. In spite of that, bleaching of Au-doped nanocomposite sol-gel glass film on a soda-lime glass substrate is demonstrated in which electric-field thermal poling is employed to effectively dissolve randomly distributed gold nanoparticles (15 nm in diameter)

Francesco P. Mezzapesa; Isabel C. S. Carvalho; Peter G. Kazansky; Olivier Deparis; Mitsuhiro Kawazu; Koichi Sakaguchi

2006-01-01

350

Metal nanocrystal memory with sol–gel derived HfO 2 high-? tunnel oxide  

Microsoft Academic Search

An all-solution processed metal–oxide–semiconductor (MOS) capacitor structure containing gold (Au) nanoparticles (NPs) within HfO2 high-? oxide was fabricated. The ultra-thin (~10nm) HfO2 high-? tunnel oxide layer was prepared by sol–gel process and showed good electrical properties, which were critical to superior memory property of the MOS structure. Au NPs with particle size of about 3.3nm were synthesized by chemical reduction

Ching-Chich Leu; Shih-Tang Chen; Fu-Ken Liu

2011-01-01

351

Microstructural characterization of gold-doped silica-titania sol-gel films  

Microsoft Academic Search

Silica-titania coatings (up to 1.7 ?m thick) doped with gold metal particles were prepared via the sol-gel method. Acid-catalyzed solutions of methyltriethoxysilane and tetrabutoxytitanate were used as precursors. Gold nanoparticles were obtained in the oxide matrix by thermal reduction. The dimension and the shape of the particles were observed by high-resolution transmission electron microscopy and X-ray diffraction. The particles were

P. Innocenzi; G. Brusatin; A. Martucci; K. Urabe

1996-01-01

352

Size dependent electrocatalytic activity of gold nanoparticles immobilized onto three dimensional sol–gel network  

Microsoft Academic Search

The electrocatalytic activity of different sizes (2.6, 12.6, 20, 40 and 60nm) of gold nanoparticles (AuNPs) immobilized onto (3-mercaptopropyl)-trimethoxysilane sol–gel modified Au electrodes (Au-MPTS) were examined by taking biologically important compounds such as ascorbic acid (AA), uric acid (UA) and 3,4-dihydroxyphenylacetic acid (DOPAC). The oxidation current of these compounds decreases and the oxidation potentials of them were shifted to more

Palraj Kalimuthu; S. Abraham John

2008-01-01

353

In situ silica reinforcement of natural rubber by sol–gel process via rubber solution  

Microsoft Academic Search

The in situ silica filling of natural rubber (NR) was carried out via the sol–gel reaction using tetraethoxysilane. The effect\\u000a of the in situ silica content on the curing, mechanical, dynamic mechanical and thermal properties of the composite vulcanizate\\u000a materials was investigated in comparison to that with a commercial silica preparation. The Mooney viscosity of the in situ\\u000a silica filled

Benjawan Chaichua; Pattarapan Prasassarakich; Sirilux Poompradub

2009-01-01

354

A gold nanoparticles\\/sol–gel composite architecture for encapsulation of immunoconjugate for reagentless electrochemical immunoassay  

Microsoft Academic Search

A highly hydrophilic, non-toxic and conductive colloidal gold nanoparticle\\/titania sol–gel composite membrane with a low contact angle was prepared on a glassy carbon electrode via a vapor deposition method. With human chorionic gonadotrophin (hCG) as a model antigen and encapsulation of horseradish peroxidase-labeled hCG antibody (HRP-anti-hCG) in the composite architecture, this membrane could be used for reagentless electrochemical immunoassay. It

Jin Chen; Jinhai Tang; Feng Yan; Huangxian Ju

2006-01-01

355

Facile Fabrication of Gold Nanoparticle-Titanium Oxide Alternate Assemblies by Surface Sol-Gel Process  

Microsoft Academic Search

Multistructured assemblies consisting of gold nanoparticles and titanium oxide were alternately fabricated by a surface sol-gel process. First, a quartz glass substrate was immersed into an organic solution of titanium butoxide [Ti(OBu)4]. Then, the substrate was rinsed with water, and dried in air, giving ultra-thin titanium oxide [Ti(O)]-modified quartz glass substrate. This modified glass substrate was immersed into an aqueous

Taichi Arakawa; Tomoaki Kawahara; Tsuyoshi Akiyama; Sunao Yamada

2007-01-01

356

DEVELOPMENT OF SOL-GEL-BASED BIOACTIVE PAPER SENSING PLATFORMS TOWARD NEUROTOXIN DETECTION  

Microsoft Academic Search

We report on a new solid-phase colorimetric bioassay format based on enzyme-catalyzed enlargement of gold nanoparticles (AuNP) that are coentrapped with the enzyme in a sol-gel based silica material. Biocatalysed hydrolysis of the enzyme substrate, acetylthiocholine (ATCh) leads to formation of thiocholine, which in turn reduces Au(III) onto the entrapped nanoparticles, producing particle growth and a concomitant increase in color

Roger Elliot Luckham

2009-01-01

357

Sol–Gel\\/Chitosan\\/Gold Nanoparticle-Modified Electrode in Mediated Bacterial Biosensor  

Microsoft Academic Search

A mediated whole cell biosensor was designed and characterized using glucose as the substrate. Gluconobacter oxydans cells were immobilized on the graphite electrode via sol–gel (tetraethyl orthosilicate)\\/chitosan hybrid composite modified\\u000a with gold nanoparticles (TEOS\\/CHIT\\/AuNPs\\/G. oxydans). A soluble mediator, potassium hexacyanoferrate (III), was used for the amperometric detection of the respiratory activity\\u000a of the intact bacterial cells. After optimization of preparation

Omer Habib; Dilek Odaci Demirkol; Suna Timur

358

Preparation and characterization of photosensitive silica sol-gel glasses containing gold and cerium  

Microsoft Academic Search

Photosensitive silica sol-gel glasses containing gold and cerium have been produced for the first time. Two methods for producing gold colloids in these glasses were employed, one using exposure to ultraviolet radiation only, a second using a UV treatment followed by a thermal treatment. The photosensitive process was studied using UV-Visible absorption, fluorescence spectroscopy and transmission electron microscopy (TEM). UV-Visible

Douglas Michael Korwin

2000-01-01

359

A sol-gel method to prepare pure and gold colloid doped ZnO films  

Microsoft Academic Search

Pure ZnO films and Au nanoparticles dispersed ZnO films were prepared by the sol-gel dip-coating technique. Thermal behavior and chemical composition of the dried ZnO precursor were investigated by thermogravimetry-differencial scanning calorimetry (TG-DSC) and Fourier transform infrared spectroscopy. The films were characterized by X-ray diffraction, scanning electronic microscopy and optical absorption measurements. Different aging times for the precursor solution at

Xiang-Hua Wang; Jianlin Shi; Shugang Dai; Yong Yang

2003-01-01

360

Synthesis, structural and electrical characterization of PbS NCs in titania sol–gel films  

Microsoft Academic Search

Nanocrystals of lead sulfide were grown in TiO2 (titania) thin films prepared by a sol-gel process. The synthetic procedure as well as the structural, optical, and electrical\\u000a properties of the films are demonstrated. The structures and morphology of PbS nanocrystals were analyzed using HRTEM, SAED,\\u000a AFM, HRSEM, XRD and EDAX elemental analysis technique. When the concentration of PbS in the

Tsiala Saraidarov; A. Gevorgian; R. Reisfeld; A. Sashchiuk; M. Bashouti; E. Lifshitz

2007-01-01

361

Size control and characterization of Au nanoparticle agglomeration during encapsulation in sol–gel matrices  

Microsoft Academic Search

Gold nanoparticles were encapsulated in sol–gel matrices with different amine cross-linker molecules in order to determine the cross-linker influence on nanoparticle agglomeration behaviour during encapsulation. The role of a stabilizing surfactant (SDS) was also investigated. The NP aggregate sizes were tracked using the UV surface plasmon resonance band (SPR), which red-shifts with increased particle size. It was found that use

Adam C. Malcolm; J. Mark Parnis; Andrew J. Vreugdenhil

2011-01-01

362

A novel capacitive immunosensor based on gold colloid monolayers associated with a sol–gel matrix  

Microsoft Academic Search

A capacitive sensing method based on self-assembling gold nanoparticles to the surface of the sol–gel modified electrode has been developed for the direct detection of the human IgG in human serum. The capacitance of the immunosensor corresponding to the concentration of human IgG is investigated by alternating current impedance. The formed mercaptopropyltriethoxysilane (MPTS) film is ultrathin; the immobilization density of

Zai-Sheng Wu; Ji-Shan Li; Ming-Hui Luo; Guo-Li Shen; Ru-Qin Yu

2005-01-01

363

Gold nanoparticles embedded in silica sol–gel matrix as an amperometric sensor for hydrogen peroxide  

Microsoft Academic Search

Gold nanoparticles (Aunp) embedded in methyltrimethoxysilane sol–gel (SG) film coated electrode was prepared (GC\\/SG-Aunp) and characterized. The electrochemical response observed for the GC\\/SG-Aunp electrode reveals that the dispersed gold nanoparticles in the silicate film are in electrical contact with each other. The potassium ferricyanide redox couple was used as a marker to probe the tunable kinetic barrier of the gold

Govindhan Maduraiveeran; Ramasamy Ramaraj

2007-01-01

364

Optical and Conductivity Properties of PbS Nanocrystals in Amorphous Zirconia Sol-Gel Films  

Microsoft Academic Search

Lead sulfide (PbS) nanocrystals (NCs), embedded in amorphous zirconia sol-gel film with different PbS mole concentration (5–30%), were grown at temperature, ranging from 200°C to 350°C. The size of PbS NCs was determined by TEM and by blue shift of the absorption edge. The size increased with an increase of the synthesis temperature and PbS mole concentration. The optical and

Aldona Sashchiuk; Efrat Lifshitz; Renata Reisfeld; Tsiala Saraidarov; Marina Zelner; Avi Willenz

2002-01-01

365

Metal nanocrystal memory with sol-gel derived HfO2 high-? tunneling oxide  

Microsoft Academic Search

A metal-oxide-semiconductor (MOS) capacitor structure containing gold (Au) nanoparticles (NPs) within sol-gel derived HfO2 high-? oxide is fabricated. Firstly, the Au NPs with particle size of about 3.3 nm were synthesized by chemical reduction method. Then the 10 nm-thick HfO2 tunneling oxide, the Au NPs and the 15 nm-thick HfO2 control oxide were prepared by spin coating method to construct

Shih-Tang Chen; Kun-Cheng Huang; Hua-Chiang Chen; Fu-Ken Liu; Ching-Chich Leu

2010-01-01

366

Microstructure, optical, and electrochromic properties of sol-gel nanoporous tungsten oxide films  

Microsoft Academic Search

Porous tungsten oxide films have been prepared by a nonhydrolitic sol-gel method using poly(ethylene glycol) (PEG) as a structure directing agent. The method entails the hydrolysis of an ethanolic solution of tungsten ethoxide (formed by the reaction of WCl6 with ethanol) followed by condensation and polymerization at the PEG-tungsten oxide oligometers interface. A highly porous WO3 framework was obtained after

Yahia Djaoued; P. V. Ashrit; S. Badilescu; R. Brüning

2003-01-01

367

Synthesis and characterization of silica xerogels obtained via fast sol–gel process  

Microsoft Academic Search

The synthesis and physical properties of high surface area silica xerogels obtained by a two-step sol–gel process in the absence\\u000a of supercritical conditions are reported. The hydrolysis and condensation reactions were followed by infrared spectroscopy.\\u000a The increment in the bands corresponding to silanol and hydroxyl groups suggests that the hydrolysis reaction was complete\\u000a during the first 30 min. The effect on

Guillermo Andrade-Espinosa; Vladimir Escobar-Barrios; Rene Rangel-Mendez

2010-01-01

368

A visible-light response vanadium-doped titania nanocatalyst by sol–gel method  

Microsoft Academic Search

A series of vanadium-doped TiO2 catalysts were synthesized by two modified sol–gel methods. V-doped TiO2 was found to be mainly preserved its anatase phase after calcination at 400°C. The TEM micrographs showed the sizes of primary particles were in the range of 6–20nm. The increase of vanadium doping promoted the particle growth, and enhanced “red-shift” in the UV-Vis absorption spectra.

Jeffrey C.-S Wu; Chih-Hsien Chen

2004-01-01

369

Modification of Thermo-Optic Characteristics of Sol-Gel Inorganic-Organic Hybrid Materials  

Microsoft Academic Search

The effect of the inorganic oxide network on the variation of thermo-optic characteristics (dn\\/dT) in inorganic-organic hybrid material prepared through the sol-gel process was investigated. The dn\\/dT values were negative for all samples, and decreased in magnitude with the increasing concentration of the inorganic oxide or heterometallic oxide network. The dn\\/dT also became less negative with the increase in the

Eun-Seok Kang; Woo-Soo Kim; Kwang-Soo Kim; Byeong-Soo Bae

2004-01-01

370

Sol–gel derived Li–V–Mn–O spinels as cathodes for rechargeable lithium batteries  

Microsoft Academic Search

Nearly stoichiometric ternary Li–V–Mn–O spinels were prepared by a sol–gel method using propionic acid to form the resin framework, and subsequent calcination of the gel at 600°C. The resulting material was tested as cathode over the voltage range 5.2–2.0 V in lithium cells. The profiles of the discharge–charge processes were found to be surprisingly similar to that recently reported for

L Hernán; J Morales; L Sánchez; J Santos; E Rodr??guez Castellón

2000-01-01

371

Preparation and characterization of sol–gel derived ZnTiO 3 nanocrystals  

Microsoft Academic Search

Nanometer scale cubic ZnTiO3 has been synthesized by sol–gel method at a lower temperature (600°C). X-ray diffraction (XRD) analysis shows that the average crystalline size of the sample is ?8–10nm. The cubic to hexagonal phase transition of ZnTiO3 is clearly observed from the XRD patterns of the sample. The thermal behavior of the sample was characterized by the thermogravimetric\\/differenthermal analysis

Shu Fen Wang; Feng Gu; Meng Kai Lü; Chun Feng Song; Su Wen Liu; Dong Xu; Duo Rong Yuan

2003-01-01

372

Photoluminescence of sol–gel derived ZnTiO 3:Ni 2+ nanocrystals  

Microsoft Academic Search

Cubic ZnTiO3 nanocrystal doped with Ni2+ ion has been synthesized by sol–gel method at a lower temperature (600 °C). The crystallinity of the doped sample was characterized by the X-ray diffraction (XRD) patterns and the infrared spectra (IR). The photoluminescence (PL) spectra of the sample measured at different excitation wavelength reveal a novel luminescent phenomenon in blue, green and red

Shu Fen Wang; Feng Gu; Meng Kai Lü; Chun Feng Song; Dong Xu; Duo Rong Yuan; Su Wen Liu

2003-01-01

373

Synthesis and characterization of zinc titanate nano-crystal powders by sol–gel technique  

Microsoft Academic Search

A sol–gel technique including the Pechini process has been employed for the preparation of nano-sized zinc titanate (ZnTiO3) powders. The yielding powders were heated at temperature from 500°C to 1000°C for various times. The ZnTiO3 phase was formed at the beginning of 500°C. The shape of crystalline will be changed from granular to fiber as the calcination temperature increasing from

Yee-Shin Chang; Yen-Hwei Chang; In-Gann Chen; Guo-Ju Chen; Yin-Lai Chai

2002-01-01

374

Preparation and Characterizations of ZnTiO 3 Powders by Sol–Gel Process  

Microsoft Academic Search

ZnTiO3 powders were prepared by a sol–gel method. The gelation conditions and the gelation mechanism were investigated. The crystallization behavior and characteristics of the ZnTiO3 were also investigated in detail. The experimental results show that homogenous and translucent gels can be prepared when the gelation conditions are appropriate and the gelation temperature remains constant. The gel structure can be described

Lili Zhao; Fangqin Liu; Xuewen Wang; Zhiyong Zhang; Junfeng Yan

2005-01-01

375

Optical characterization of ZnO thin films deposited by Sol-gel method  

Microsoft Academic Search

In this paper, ZnO thin film is deposited on Pt\\/TiO2\\/SiO2\\/Si substrate using the sol-gel method and the effect of annealing temperature on the structural morphology and optical properties of ZnO thin films is investigated. The ZnO thin films are crystallized by the heat treatment at over 400C. The ZnO thin film annealed at 600C exhibits the greatest c-axis orientation and

Byeong Kyun Choi; Dong Hoon Chang; Yung Sup Yoon; Seong Jun Kang

2006-01-01

376

Fabrication and Characterization of Aqueous Sol-Gel LaFeO3 Thin Films  

Microsoft Academic Search

A novel all-inorganic aqueous sol-gel process has been developed to fabricate LaFeO3 thin films by dip-coating. Stable, positively charged colloidal sol particles of hydrous lanthanum ferrite with an average particle size (Zav) of 7 nm were prepared and coated onto quartz plates under controlled conditions. The sols have been characterized using photon correlation spectroscopy (PCS) for Zav and size distribution.

M. Rajendran; M. Ghanashyam Krishna; A. K. Bhattacharya

2000-01-01

377

Preparation of core shell particles consisting of cobalt ferrite and silica by sol–gel process  

Microsoft Academic Search

Core shell particles consisting of a magnetic core of cobalt ferrite (CoFe2O4) and a shell of silica (SiO2) are prepared by sol–gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of ferrite. The core shell structure is confirmed by TEM. The magnetic properties of these nanocomposites are measured by PPMS in low temperature and

Shuping Zhang; Dawei Dong; Yu Sui; Zhiguo Liu; Hongxia Wang; Zhengnan Qian; Wenhui Su

2006-01-01

378

Preparation of epitaxial LiNbO3 films by the sol-gel method  

Microsoft Academic Search

The effect of substrates on the crystallinity and interdiffusion behaviors in sol-gel derived LiNbO3 films were investigated using X-ray diffraction, transmission electron microscopy and secondary ion mass spectroscopy. The epitaxial films were obtained on (0001)-sapphire, (0001)-LiTaO3 and (0001)-5%MgO doped LiNbO 3 substrates with similar crystal structures, but with a variety of lattice constants. When sapphire, which has the largest lattice

K. Terabe; N. Iyi; H. Uematsu; I. Sakaguchi; Y. Matsui; K. Kitamura; S. Kimura

1994-01-01

379

Maghemite silica nanocomposites: sol gel processing enhancement of the magneto-optical response  

Microsoft Academic Search

The preparation and processing of maghemite-silica gel nanocomposites have been investigated in order to maximize their magneto-optical response for magnetic field sensing applications. In situ precipitation of maghemite nanoparticles from an iron salt precursor during the sol-gel processing of the silica matrix has been carried out while controlling the time, temperature, and environment at each step of the whole process.

D. Ortega; R. García; R. Marín; C. Barrera-Solano; E. Blanco; M. Domínguez; M. Ramírez-del-Solar

2008-01-01

380

Patterned growth of ZnO nanorods by micromolding of sol-gel-derived seed layer  

Microsoft Academic Search

An effective method for fabricating micropatterned ZnO nanorods without a catalyst via hydrothermal synthesis using a micromolding technique is presented. Micromolding of a sol-gel-derived seed layer was flawlessly accomplished by conformal contact of elastic mold with microscale pattern. The patterned growth of the nanorods over a large area of the preconfined seed layer was observed with a pattern feasibility attaining

S. Joon Kwon; Jae-Hwan Park; Jae-Gwan Park

2005-01-01

381

ZnO nanorods on ZnO seed layer derived by sol–gel process  

Microsoft Academic Search

Well-aligned ZnO nanorods are obtained by a liquid phase epitaxial growth on the indium-doped tin oxide glass deposited with\\u000a a ZnO thin film as the seed layer, which is prepared by combining a sol–gel process and a spin coating technique. The effects\\u000a of water content in the sol and heat treatment temperature on the properties of the ZnO thin film

Y. T. Yin; W. X. Que; C. H. Kam

2010-01-01

382

Optical properties of some sol–gel-derived gallium-doped ZnO films  

Microsoft Academic Search

Gallium-doped zinc oxide (ZnO) films with different concentrations have been prepared by sol–gel technique. The films are optically transparent and electrically conducting. The optical transmission and reflection data for the films have been analyzed. The optical absorption coefficient (?) and hence the refractive index (n), extinction coefficient (k) and the band gap (Eg) have been determined for these films using

G. K Paul; S. K Sen

2002-01-01

383

Sol–gel based fabrication of hybrid microfluidic devices composed of PDMS and thermoplastic substrates  

Microsoft Academic Search

Fabrication of microfluidic devices using both rigid and flexible plastic substrates offers benefits for making pressure-actuated membrane valves, mechanically active components, and low-cost but highly functional 3D microchannel networks. Here we present a simple and versatile process for bonding flexible polydimethylsiloxane (PDMS) and rigid thermoplastics like poly(methyl methacrylate) (PMMA), by utilizing the sol–gel method. The silica sol, obtained by oligomerizing

Yusuke Suzuki; Masumi Yamada; Minoru Seki

2010-01-01

384

Bismuth titanate thin film for pressure sensor prepared by sol gel method  

Microsoft Academic Search

Bismuth titanate, Bi4Ti3O12 thin film pressure sensor was fabricated by sol gel method. The Bi4Ti3O12 thin film was synthesized on substrate Si\\/ SiO2 \\/ RuO2 at low temperature to avoid short-circuit problem. The film was obtained by depositing multiple Bi-Ti-O spin coat layers on substrate, followed by heating of each layer at 300 C in air for 15 mins. Ag

Chong Cheong Wei; M. Yahaya; M. M. Salleh

2004-01-01

385

Optically active erbium-doped waveguides fabricated using a single-sol-gel-deposition technique  

Microsoft Academic Search

We present the results of optical-characterization experiments conducted on optically active erbium-doped waveguides. Using selected characterization results presented in this paper and a simple analysis, the device operation is evaluated. Each of the core and the cladding layers were individually fabricated using a single sol-gel deposition. These are, to the best of our knowledge, the first optically active waveguides to

Robert R. Thomson; Henry T. Bookey; H. Ur-Rehman; S. Liu; N. Suyal; Ajoy K. Kar

2005-01-01

386

Electrochromic properties of lithium doped WO 3 films prepared by the sol–gel process  

Microsoft Academic Search

The electrochemical responses of amorphous thin films of lithium doped tungsten trioxide (LixWO3) prepared by the sol–gel method were studied. The electrode mass change in the oxide films during cyclic voltammetry and chronoamperometry measurements was evaluated with electrochemical quartz crystal microbalance (EQCM). The electrode mass change and electrochemical performances depend on the lithium doping level. Higher lithium doping levels lead

C. O. Avellaneda; P. R. Bueno; R. C. Faria; L. O. S. Bulhões

2001-01-01

387

Fabrication of transparent iron-oxide films by means of sol-gel synthesis (abstract)  

Microsoft Academic Search

Transparent iron-oxide films were fabricated by sol-gel synthesis using a solution of ferric nitrate (III) dissolved in ethylene glycol.1 The solution was kept at 80 °C and stirred constantly in a nitrogen atmosphere. The gel with an appropriate viscosity was spin coated on soft glass plates, then dried and heated in air at various temperatures for 5 h. The films

K. Yamaguchi; T. Fujii; S. Kuranouchi; A. Kaneko

1988-01-01

388

Electrochromic properties of nickel oxide thin films prepared by the sol-gel method  

Microsoft Academic Search

The electrochromic nickel oxide films were prepared onto transparent conducting film on glass substrate by the sol-gel method using an ethylene glycol solution of nickel nitrate hexahydrate. The films produced by the dip-coating method and calcined at 250, 300, and 350 degree(s)C. The formed films were characterized by their electrochromic behavior in cyclic voltammetry. The formed films showed electrochromic behavior

Takeshi Miki; Kazuki Yoshimura; Yutaka Tai; Masato Tazawa; Ping Jin; Sakae Tanemura

1995-01-01

389

Preparation of Pd doped WO3 films via sol-gel method and their gasochromic properties  

Microsoft Academic Search

In this paper, WO3 sol was prepared via the sol-gel method, and palladium chloride powder was dissolved in the sol in different W: Pd molar ratios. Pd doped WO3 films were coated on silicon wafers and ordinary slide glasses by dip-coating method. The grain distribution of WO3 sol doped with PdCl2 was measured by Laser Particle Size Analyzer. Surface morphology

Jichao Shi; Guangming Wu; Jun Shen; Guohua Gao; Bin Zhou; Xingyuan Ni; Xiaoyun Yang

2008-01-01

390

Preparation of PbTiO 3 by seeding-assisted chemical sol-gel  

Microsoft Academic Search

Lead Titanate has been prepared by a sol-gel method using titanium tetrabutoxide and lead acetate in stoichiometric proportion. It was found that the seeding with solid PbTiO3 nanometer-size particles (5 and 10 wt%) into the precursor solution plays a crucial role during crystallisation. At 380° and 400°C, the fraction of crystallisation of the PbTiO3 perovskite phase for seeded sample is

J Tartaj; J. F Fernández; M. E Villafuerte-Castrejón

2001-01-01

391

Dielectric and magnetic properties of sol-gel-derived lead iron niobate ceramics  

Microsoft Academic Search

In this work, we report the synthesis of sol-gel-derived lead iron niobate [Pb1.10(Fe0.5Nb0.5)O3] (PFN) powders and sintered ceramics. The PFN powders were calcined at (Ta), 973, 1073, 1173, 1273, and 1373 K for 3 h in air. As envisaged from x-ray-diffraction analyses, PFN powder calcined at 1173 K was crystallized into pure monoclinic perovskite phase whereas powders calcined at all

S. B. Majumder; S. Bhattacharyya; R. S. Katiyar; A. Manivannan; P. Dutta; M. S. Seehra

2006-01-01

392

A lipophilic sol-gel matrix for the development of a carbonate-selective electrode.  

PubMed

Organic-inorganic hybrid sol-gel matrixes were used as hosts for trifluoroacetyl-p-decylbenzene (TFADB), a traditional ionophore for carbonate. The sol-gel precursor was prepared by the reaction of (3-isocyanopropyl)triethoxysilane with ethylene glycol. Hexadecyltrimethoxysilane (HDTMOS) was employed as a co-precursor. An appropriate amount of tridodecylmethylammonium chloride (TDMAC) and 2-nitrophenyloctyl ether (NPOE) were used as membrane components. On mixing with an acidic catalyst, the sol-state precursors slowly gelled, yielding a membrane in which the active components, TFADB and TDMAC, were encapsulated. Infrared, (1)H, and (29)Si MAS NMR spectrometers were employed to monitor the sol-gel process and the degree of polymerization. The performances of the sol-gel membrane-based electrodes were compared to those of TFADB-based poly(vinyl chloride) (PVC) membrane electrodes. Membranes with a molar ratio of TFADB:TDMAC (1:0.14) showed extended lifetime and stable baseline potential. The response slope toward carbonate was approximately 27 mV/decade between 10(-)(5) and 10(-)(3.5) M at 18 degrees C. Interestingly, selectivity toward carbonate over salicylate and other lipophilic anions was improved, clearly deviating from the Hofmeister selectivity pattern. Responses toward small inorganic anions including chloride and sulfate were negligible. The selectivity coefficients measured by the matched potential method in 0.1 M tris-sulfuric acid buffer, pH 8.75, were log = -0.3, log = -4.2, and log = -2.5. PMID:15481966

Lee, Byung Hwa; Shim, Yoon-Bo; Park, Sung Bae

2004-10-15

393

Sol–gel synthesis and properties of multiferroic BiFeO 3  

Microsoft Academic Search

High purity multiferroic BiFeO3 (BFO) powders were synthesized by sol–gel process using bismuth nitrate and iron nitrate as sources. The BFO powders annealed at 600 °C in nitrogen environment were mainly composed of a rhombohedral BiFeO3 phase (R-phase) with a minor impurity phase of Bi2O3. A pure BFO R-phase has been obtained by leaching out the minor Bi2O3 phase using

Jong Kuk Kim; Sang Su Kim; Won-Jeong Kim

2005-01-01

394

Characterization of Sol-gel Encapsulated Proteins using Small-angle Neutron Scattering  

SciTech Connect

Entrapment of biomolecules in silica-derived sol-gels has grown into a vibrant area of research since it was originally demonstrated. However, accessing the consequences of entrapment on biomolecules and the gel structure remains a major challenge in characterizing these biohybrid materials. We present the first demonstration that it is possible with small-angle neutron scattering (SANS) to study the conformation of dilute proteins that are entrapped in transparent and dense sol-gels. Using deuterium-labeled green fluorescent protein (GFP) and SANS with contrast variation, we demonstrate that the scattering signatures of the sol-gel and the protein can be separated. Analysis of the scattering curves of the sol-gels using a mass-fractal model shows that the size of the colloidal silica particles and the fractal dimensions of the gels were similar in the absence and presence of protein, demonstrating that GFP did not influence the reaction pathway for the formation of the gel. The major structural difference in the gels was that the pore size was increased 2-fold in the presence of the protein. At the contrast match point for silica, the scattering signal from GFP inside the gel became distinguishable over a wide q range. Simulated scattering curves representing a monomer, end-to-end dimer, and parallel dimer of the protein were calculated and compared to the experimental data. Our results show that the most likely structure of GFP is that of an end-to-end dimer. This approach can be readily applied and holds great potential for the structural characterization of complex biohybrid and other materials.

Luo, Guangming [ORNL; Zhang, Qiu [ORNL; Del Castillo, Alexis Rae [ORNL; Urban, Volker S [ORNL; O'Neill, Hugh Michael [ORNL

2009-01-01

395

Sol–gel encapsulated cobalt(III) acetylacetonate for air oxidation of penicillin derivatives  

Microsoft Academic Search

The sulfoxides of penicillin derivatives are important pharmaceutical intermediates and can be prepared by air oxidation of corresponding sulfides catalyzed by cobalt(III) acetylacetonate (Co(acac)3). However, when using the homogeneous catalyst, it is very difficult to separate the catalyst from product, which makes it impossible to reuse the catalyst directly. While the heterogeneous Co(acac)3 encapsulated by sol–gel method can solve the

Qiuyi Hu; Jiquan Zhao; Yanji Wang; Lingdi Zhu; Mengqing Li; Guohua Li; Yang Wang; Fengyan Ge

2003-01-01

396

Surface characterization of sol-gel derived scintillating rare-earth doped Lu2SiO5 thin films  

E-print Network

Surface characterization of sol-gel derived scintillating rare- earth doped Lu2SiO5 thin films C-marie.nedelec@univ-bpclermont.fr Abstract. Rare earth doped Lu2SiO5 thin films have been prepared by combining sol-gel process and spin of rare earth doping ions. XPS and RBS spectrocopies showed that the composition of the films is close

Paris-Sud XI, Université de

397

Synthesis and characterization of sol-gel-derived tantalum oxide, tantalum nitride, and nickel-alumina thin films  

Microsoft Academic Search

Sol-gel processing techniques provide an economical, reliable and highly versatile method for producing a wide variety of materials. This thesis explores the synthesis and characterization of tantalum oxide, tantalum nitride, and nickel-alumina thin films produced by sol-gel techniques. Tantalum oxide thin film capacitors are of particular interest because of their high dielectric constant and good breakdown strength. Replacing the discrete

Gerald Thomas Kraus

1997-01-01

398

Colorimetric bismuth determination in pharmaceuticals using a xylenol orange sol–gel sensor coupled to a multicommutated flow system  

Microsoft Academic Search

A new sol–gel Bi(III) sensor was developed by incorporating xylenol orange (XO) into sol–gel thin films (<1?m thick) coated on glass slides. Several sols were produced in order to evaluate the effect of different processing parameters on the final characteristics of the sensor. Sensor films based on tetramethoxysilane (TMOS) as precursor, nitric acid catalysis, water:alkoxide ratio of 2 and XO

Paula C. A. Jerónimo; Alberto N. Araújo; M. Conceição B. S. M. Montenegro; Dalibor Satinský; Petr Solich

2004-01-01

399

Size variation and optical absorption of sol-gel Ag nanoparticles doped SiO 2 thin film  

Microsoft Academic Search

In this research, we have focused on the formation of Ag nanoparticles dispersed in SiO2 matrix using sol-gel method. The influences of the metal concentration on the size variation of Ag nanoparticles and the size effect on the surface plasmon absorption have been studied. Sol-gel silica thin films containing Ag particles were synthesized by dip-coating on soda-lime glasses. The molar

A. Babapour; O. Akhavan; A. Z. Moshfegh; A. A. Hosseini

2006-01-01

400

Preparation of spherical alumina and copper oxide coated alumina sorbents by improved sol–gel granulation process  

Microsoft Academic Search

Granular alumina (Al2O3) and copper coated Al2O3 sorbents were prepared by a continuous sol–gel process that could be the basis of a large-scale plant for production of the new sorbents by the sol–gel method. This continuous fabrication process allows the production of the sorbents in a larger quantity as well as in a more consistent shape and size. In addition,

Genoveva Buelna; Y. S Lin

2001-01-01

401

Immobilization of acetylcholinesterase on gold nanoparticles embedded in sol–gel film for amperometric detection of organophosphorous insecticide  

Microsoft Academic Search

A simple method to immobilize acetylcholinesterase (AChE) on silica sol–gel (SiSG) film assembling gold nanoparticles (AuNPs) was proposed, thus a sensitive, fast and stable amperometric sensor for quantitative determination of organophosphorous insecticide was developed. The large quantities of hydroxyl groups in the sol–gel composite provided a biocompatible microenvironment around enzyme molecule and stabilized its biological activity to a large extent.

Dan Du; Shizhen Chen; Jie Cai; Aidong Zhang

2007-01-01

402

Optical activation of patterned Si nanowires grown from sol–gel prepared gold\\/Er-doped aluminous film  

Microsoft Academic Search

Optical activation of patterned Si nanowires grown from sol–gel prepared gold\\/Er-doped aluminous film is investigated. The growth of patterned Si nanowires (SiNWs), the doping of Er ions and the sintered process are completed by one step. Si nanowires were grown from a sol–gel solution containing both Au catalysts and Er ions by the vapor–liquid–solid method. Such Er-activated Si nanowires achieve

Lingling Ren; Won young Jeung; Heon-Jin Choi

2007-01-01

403

Electrochemical impedance behavior of DNA biosensor based on colloidal Ag and bilayer two-dimensional sol–gel as matrices  

Microsoft Academic Search

A novel method for fabrication of DNA biosensors has been developed by means of self-assembling colloidal Ag (Ag) to a thiol-containing sol–gel network. The thiol groups of 3-mercaptopropyltrimethoxysilane (MPTS) serve as binding sites for the covalent attachment to gold electrode surface. Then the one-dimensional network of silane unites (1dMPTS) was combined together into a two-dimensional sol–gel network (2dMPTS) by dipping

Yingzi Fu; Ruo Yuan; Lan Xu; Yaqin Chai; Yan Liu; Dianping Tang; Ying Zhang

2005-01-01

404

A facile sol–gel method for the encapsulation of gold nanoclusters in silica gels and their optical properties  

Microsoft Academic Search

A novel process consisting of a synthesis of gold hydrosol using tetrakis (hydroxymethyl) phosphonium chloride (THPC) reduction and a sol–gel process using tetramethylorthosilicate (TMOS) for the encapsulation of gold nanoparticles (Au\\/SiO2: 0.1–1 wt% Au) in a matrix of silica gel without the aid of any external stabilizing agent or organically modified sol–gel monomers is described. The optical absorption spectra showed

S Tamil Selvan; Masayuki Nogami; Arao Nakamura; Yasushi Hamanaka

1999-01-01

405

MICROWAVE CHARACTERIZATION OF HYDROTHERMALLY CRYSTALLIZED BARIUM STRONTIUM TITANATE SOL-GEL COMPOSITE THIN FILMS USING A COPLANAR WAVEGUIDE TECHNIQUE  

Microsoft Academic Search

Barium strontium titanate (BST) and BST doped with 5 at% Mn films have been fabricated on gold-patterned alumina substrates by hydrothermal sol-gel composite recrystallization at < 200°C. A spun-on sol-gel BST composite film is hydrothermally treated in an alkaline aqueous solution at elevated pressure. The dielectric constant and loss tangent between 5 and 40 GHz has been determined using the

KIM ZELONKA; MICHAEL SAYER; HANY F. HAMMAD; ALOIS P. FREUNDORFER; YAHIA ANTAR

2007-01-01

406

Sol-gel nanocasting synthesis of patterned hierarchical LaFeO3 fibers with enhanced catalytic CO oxidation activity.  

PubMed

Hierarchical LaFeO3 fibers were prepared by a sol-gel nanocasting method using a cotton cloth as the template. The resulting LaFeO3 fibers inherited the initial network morphology of the template very well and showed enhanced catalytic CO oxidation activity and satisfactory stability compared to the counterpart particles prepared by the conventional sol-gel method. PMID:21234504

Li, Pengna; Hu, Xianluo; Zhang, Lei; Dai, Hongxing; Zhang, Lizhi

2011-03-01

407

The sol–gel transition of mullite spinning solution in relation to the formation of ceramic fibers  

Microsoft Academic Search

Continuous mullite ceramic fibers were fabricated by a sol–gel dry spinning technique. The sol was prepared from an aqueous\\u000a solution of aluminum nitrate (AN), aluminum isopropoxide (AIP) and tetraethylorthosilicate (TEOS). The sol–gel transition\\u000a was investigated by measuring the volume, the solid content, the viscosity and the rheological properties of the solution.\\u000a Shear viscosity ? of the mullite sol varied dynamically

Xintuo Chen; Lixia Gu

2008-01-01

408

Ferroelectric ceramics with compositions close to LiTaO3, obtained from powders prepared by a sol-gel  

Microsoft Academic Search

Powders with compositions close to LiTaO3 have been prepared by a sol-gel method using alcoholates of Iithium and tantalum. The granulometry of these powders obtained allowed us to elaborate ceramics at temperatures lower than 1150°C. Comparative dilatometries from sol-gel or solid state reaction powders showed the shrinkage coefficient to be higher and the sintering temperature to be lower in the

Jean Ravez; Nadine Puyoo-Castaings; Francoise Duboudin

1988-01-01

409

Low-temperature crystallization of oriented ZnO film using seed layers prepared by sol–gel method  

Microsoft Academic Search

Transparent zinc oxide (ZnO) films were coated on seed layers prepared by the sol–gel method by chemical solution deposition\\u000a method. Firstly, seed layers were prepared from zinc acetate and monoethanolamine, 2-methoxyethanol by the sol–gel method\\u000a on a silicon substrate or a slide glass. Next, the substrate coated with a seed layer was immersed in zinc nitride solution\\u000a with hexamethylenetetramine, and

Hiroyo Segawa; Hideaki Sakurai; Reiko Izumi; Toshiharu Hayashi; Tetsuji Yano; Shuichi Shibata

2011-01-01

410

Preparation and characterization of sol–gel bioactive glass coating for improvement of biocompatibility of human body implant  

Microsoft Academic Search

The aim of this work was preparation, development and characterization of bioactive glass coating by sol–gel technique for improvement of biocompatibility of 316L stainless steel implant used in dentistry and orthopaedic surgery.Bioglass powder was made by sol–gel technique and thermal properties of the prepared powder were studied using differential thermal analysis (DTA). The prepared bioglass powder was immersed in the

M. H. Fathi; A. Doost Mohammadi

2008-01-01

411

Optical and structural properties of sol-gel-made WO3 and Zr-doped WO3 thin films  

Microsoft Academic Search

The aim of this study was to determine the optical properties of WO3 and Zr doped tungsten oxide films deposited by the sol-gel process. The optical properties of WO3 and Zr doped tungsten oxide films deposited by the sol-gel process depend on the number of coating layers. The refractive index and absorption coefficient of WO3 thin films increases with an

Esra Ozkan; Fatma Tepehan

2000-01-01

412

Optical and structural characteristics of sol–gel-deposited tungsten oxide and vanadium-doped tungsten oxide films  

Microsoft Academic Search

The optical and structural properties of sol–gel spin-coated WO3 and Vanadium-doped WO3 thin films were investigated. These films have been produced by a sol–gel technique. The refractive index, extinction coefficient and optical band gap of the films have been calculated with respect to the number of coating layers. The surface morphology was analyzed by atomic force microscopy (AFM). Optical constants

E Özkan; F. Z Tepehan

2001-01-01

413

Rare earth doped optical fiber fabrication by standard and sol-gel derived granulated oxides  

NASA Astrophysics Data System (ADS)

We present our progress in the production of ytterbium (Yb) doped optical fibers fabricated by two variants of the granulated aluminophosphosilicate method. We show advantages and disadvantages of mixing rare earth and aluminophosphosilicate granulated oxides directly (variant 1) or by using the sol-gel method to produce doped granulate material (variant 2). For both methods we studied the effects of varying the dopant concentrations and of introducing iterative melting and milling procedures. In particular, the sol-gel based method eases the inclusion of P2O5 and thus, in combination with Al2O3, higher dopant concentration of Yb and Er are possible. Sintering the sol-gel material at high temperature eliminated bubbles in the core. We fabricated optical fibers that, piecewise, between individual strong scatterers, exhibited attenuation losses as low as 0.35dB/m. For our comparative study we determined volume percentage and distribution of chemical elements in the fabricated fiber glasses by the analytical technique of Energy-Dispersive X-ray, Electro Probe Microanalysis and the degree of crystallization by X-Ray Diffraction analysis. Furthermore we measured fluctuations of the refractive index profile and scattering losses of the fiber core.

Etissa, D.; Neff, M.; Pilz, S.; Ryser, M.; Romano, V.

2012-04-01

414

Sol gel ZnO films doped with Mg and Li evaluated for charged particle detectors  

NASA Astrophysics Data System (ADS)

In this work we assess the feasibility of ZnO films deposited from a sol gel precursor as a material for thin film charged particle detectors. There are many reports of polycrystalline ZnO thin film transistors (TFTs) in the literature, deposited by sputtering, pulsed laser deposition, and sol gel. There are also reports of sol gel derived ZnO doped with Li or Mg to increase the resistivity, however, these works only measure resistivity of the films, without determining the effect of doping on the carrier concentration. We study the effects of doping the ZnO with Mg and Li as well as the effects of thickness on the films' resistivity, mobility, and carrier concentration, since these material parameters are critical for a charged particle sensor. Carrier concentration is particularly important because it must be kept low in order for the intrinsic region of a p-i-n diode to be depleted. In order to accomplish this we fabricate and electrically characterize test structures for resistivity, test structures for hall measurement, common back-gate TFTs, and metal-insulator-semiconductor (MIS) capacitors. We also conduct physical characterization techniques such as x-ray diffraction (XRD), atomic force microscopy (AFM), electron microscopy, UV-Vis spectroscopy, and ellipsometry to determine the effect of doping and film thickness on the microstructure and optical properties of the ZnO.

Murphy, John W.; Eddy, Alexander; Kunnen, George R.; Mejia, Israel; Cantley, Kurtis D.; Allee, David R.; Quevedo-Lopez, Manuel A.; Gnade, Bruce E.

2013-05-01

415

Facile Fabrication of Gold Nanoparticle-Titanium Oxide Alternate Assemblies by Surface Sol-Gel Process  

NASA Astrophysics Data System (ADS)

Multistructured assemblies consisting of gold nanoparticles and titanium oxide were alternately fabricated by a surface sol-gel process. First, a quartz glass substrate was immersed into an organic solution of titanium butoxide [Ti(OBu)4]. Then, the substrate was rinsed with water, and dried in air, giving ultra-thin titanium oxide [Ti(O)]-modified quartz glass substrate. This modified glass substrate was immersed into an aqueous colloidal solution of gold nanoparticles (AuPs) that were stabilized with citrate ions, giving a AuP-Ti(O)-modified glass substrate. By repeating these surface sol-gel processes, the multistructured assemblies of AuPs and Ti(O), [AuP/Ti(O)]n/Glass (n=1--4) were fabricated. Plasmon band intensity increased with the number of surface sol-gel process cycles. The resultant assemblies were stable even after 11 days, or after treatment with an aqueous electrolyte solution. The alternate assembling of AuPs and Ti(O) was confirmed by quartz crystal microbalance measurements and absorption and X-ray photoelectron spectroscopies. Accordingly, we have succeeded in the preparation of stable AuP-Ti(O) composite films on the substrates.

Arakawa, Taichi; Kawahara, Tomoaki; Akiyama, Tsuyoshi; Yamada, Sunao

2007-04-01

416

Fabrication of superhydrophobic sol-gel composite films using hydrophobically modified colloidal zinc hydroxide.  

PubMed

A superhydrophobic sol-gel composite film was fabricated by incorporating hydrophobically modified colloidal zinc hydroxide (CZH) in sol-gel matrix. CZH was prepared by controlled precipitation and modified by treatment with stearic acid. The concentration of stearic acid and stirring time were optimized to obtain modified CZH with very high water contact angle (WCA) of 165 degrees and sliding angle (SA)<2 degrees . X-ray diffraction (XRD) analysis has shown that the crystal structure of CZH was mainly composed of epsilon-zinc hydroxide and the modified CZH indicated the presence of zinc stearate. The modified CZH film exhibited a microstructure which resembled clusters of interconnected rods creating roughness on the film surface. The modified CZH suspension was dispersed in an acid-catalyzed sol of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) and spray-coated on glass slides to prepare sol-gel composite coatings. The concentration of CZH in the composite film was optimized to obtain superhydrophobic surfaces. FTIR spectrum also confirmed the presence of zinc stearate in the composite film. The method is simple and cost-effective and does not involve any expensive chemicals or equipments. PMID:19720382

Lakshmi, R V; Basu, Bharathibai J

2009-11-15

417

Use of sol-gel-derived titania coating for direct soft tissue attachment.  

PubMed

A firm bond between an implant and the surrounding soft tissue is important for the performance of many medical devices (e.g., stents, canyls, and dental implants). In this study, the performance of nonresorbable and reactive sol-gel-derived nano-porous titania (TiO(2)) coatings in a soft tissue environment was investigated. A direct attachment between the soft tissue and the sol-gel-derived titania coatings was found in vivo after 2 days of implantation, whereas the titanium control implants showed no evidence of soft tissue attachment. The coated implants were in immediate contact with the connective tissue, whereas the titanium controls formed a gap and a fibrous capsule on the implant-tissue interface. The good soft tissue attachment of titania coatings may result from their ability to initiate calcium phosphate nucleation and growth on their surfaces (although the formation of poorly crystalline bonelike apatite does not occur). Thus, the formation of a bonelike CaP layer is not crucial for their integration in soft tissue. The formation of bonelike apatite was hindered by the adsorption of proteins onto the initially formed amorphous calcium phosphate growth centers, thus preventing the dissolution/reprecipitation processes required for the formation of poorly crystalline bonelike apatite. These findings might open novel application areas for sol-gel-derived titania-based coatings. PMID:15227661

Areva, Sami; Paldan, Hannu; Peltola, Timo; Närhi, Timo; Jokinen, Mika; Lindén, Mika

2004-08-01

418

Novel multifunctional titania-silica-lanthanum phosphate nanocomposite coatings through an all aqueous sol-gel process.  

PubMed

A novel nanocomposite coating containing titania, silica and lanthanum phosphate prepared through an all aqueous sol-gel route exhibits excellent self-cleaning ability arising from the synergistic effect of the constituents in the nanocomposite. A highly stable titania-silica-lanthanum phosphate nanocomposite sol having particle size in the range of 30-50 nm has been synthesized starting from a titanyl sulphate precursor, which was further used for the development of photocatalytically active composite coatings on glass. The coatings prepared by the dip coating technique as well as the nanocomposite powders are heat treated and characterized further for their morphology and multifunctionality. The nanocomposite containing 1.5 wt% LaPO4 has shown a surface area as high as 138 m(2) g(-1) and a methylene blue degradation efficiency of 94% in two hours of UV exposure. The composite coating has shown very good homogeneity evidenced by transparency as high as 99.5% and low wetting behaviour. The present novel approach for energy conserving, aqueous derived, self-cleaning coatings may be suitable for large scale industrial applications. PMID:23358559

Smitha, Venu Sreekala; Jyothi, Chembolli Kunhatta; Peer, Mohamed A; Pillai, Saju; Warrier, Krishna Gopakumar

2013-04-01

419

Structural and spectroelectrochemical investigations of sol-gel derived electrochromic spinel Co{sub 3}O{sub 4} films  

SciTech Connect

Thin films of the cubic spinel Co{sub 3}O{sub 4} were prepared by the sol-gel route from a Co(II) sulfate precursor using a dip-coating technique. The films (50 to 60 nm thick) were deposited on indium-tin oxide glass substrates with a single dipping. The electrochromic properties of the films were studied in an aqueous alkaline electrolyte (0.1 M LiOH) using cyclic voltammetry (CV) and in situ UV-vis spectroelectrochemistry. The intermediate oxide products that appeared during cycling at current peak potentials were analyzed by x-ray diffraction (XRD) and ex situ Fourier transform infrared (FTIR) reflection-absorption spectroscopy performed at near-grazing incidence angle conditions (NGIA). High hydration of the spinel structure enables complex redox processes to take place inside the structure or on the surface of the film when potential cycling is performed. Vibrational bands characteristic of the formation of CoO, Co(OH){sub 2}, and hydrated Co{sub 3}O{sub 4} phases have been assigned and discussed according to the results obtained from ex situ NGIA FTIR, CV, and XRD studies. The change in transmittance ({lambda} = 634 nm) between bleached and colored states for single-dipped films was 25%, and for electrochromic efficiency ({eta}) was approximately 25 cm{sup 2}/C.

Svegl, F.; Orel, B. [National Inst. of Chemistry, Ljubljana (Slovenia); Hutchins, M.G. [Oxford Brookes Univ. (United Kingdom). School of Engineering; Kalcher, K. [Karl-Franzens Univ., Graz (Austria). Inst. of Analytical Chemistry

1996-05-01

420

Remediation of waters contaminated with MCPA by the yeasts Lipomyces starkeyi entrapped in a sol-gel zirconia matrix.  

PubMed

A single-stage sol-gel route was set to entrap yeast cells of Lipomyces starkeyi in a zirconia (ZrO(2)) matrix, and the remediation ability of the resulting catalyst toward a phenoxy acid herbicide, 4-chloro-2-methylphenoxyacetic acid (MCPA), was studied. It was found that the experimental procedure allowed a high dispersion of the microorganisms into the zirconia gel matrix; the ZrO(2) matrix exhibited a significant sorption capacity of the herbicide, and the entrapped cells showed a degradative activity toward MCPA. The combination of these effects leads to a nearly total removal efficiency (>97%) of the herbicide at 30 °C within 1 h incubation time from a solution containing a very high concentration of MCPA (200 mg L(-1)). On the basis of the experimental evidence, a removal mechanism was proposed involving in the first step the sorption of the herbicide molecules on the ZrO(2) matrix, followed by the microbial degradation operated by the entrapped yeasts, the metabolic activity of which appear enhanced under the microenvironmental conditions established within the zirconia matrix. Repeated batch tests of sorption/degradation of entrapped Lipomyces showed that the removal efficiency retained almost the same value of 97.3% after 3 batch tests, with only a subsequent slight decrease, probably due to the progressive saturation of the zirconia matrix. PMID:21077667

Sannino, Filomena; Pirozzi, Domenico; Aronne, Antonio; Fanelli, Esther; Spaccini, Riccardo; Yousuf, Abu; Pernice, Pasquale

2010-12-15

421

Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO3  

NASA Astrophysics Data System (ADS)

Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of LaxBi1-xFeO3 (LBFO) ceramics (0 ? x ? 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO3 (BFO) for x ? 0.2 but transforms to orthorhombic Pbnm structure for x > 0.2. The fundamental 12 Raman modes of pure BFO (x = 0.0) are reduced to 10 modes for x = 0.2 and further reduced to 7 modes for x = 0.4, which is a clear indication of structural modification and symmetry changes brought about by La doping. The coercive field, HC, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest HC (19.5 kOe at RT) reported so far in any rare earth doped BFO, which will have a great potential for practical application in non-volatile memory devices. Moreover, high-field magnetization and remanence, Mr, increase linearly with La doping content due to the gradual change in spin cycloid structure. M(T) curve shows an anomaly at 50 K, similar to that expected in a spin glass system. The Néel temperature (TN) of the LBFO increases with x, approaching that of the LaFeO3.

Suresh, Pittala; Srinath, S.

2013-05-01

422

Sol-gel analogous aminolysis-ammonolysis of chlorosilanes to chlorine-free Si/(C)/N-materials.  

PubMed

Large amounts of chlorosilanes, especially SiCl4 and CH3SiCl3, are produced as side-products of the industrial fabrication of solar or electronic grade silicon and the Müller-Rochow process. It was a goal of the present study to transform these compounds into useful chlorine-free precursors for Si/(C)/N ceramics via a sol-gel analogous liquid processing route. Chlorine substitution of the chlorosilanes (mixtures) with diethylamine did not yield chlorine-free products, complete reactions are only possible with lithium diethylamide. However, aminolyses with n-propylamine were successful. Transamination with ammonia was not possible with diethylaminosilanes but was with n-propylaminosilanes in various solvents. This result was attributed to steric reasons and polar interactions of the N-H groups. Colourless solid or liquid polysilazanes were obtained, depending on the silane (mixture) and the solvent. Transamination reactions of CH3Si(NH-n-Pr)3 in chloroform reproducibly yielded a cage-like oligosilazane of the composition (CH3)9Si9(NH)12N. Single crystal X-ray structure analysis revealed a seven-cyclic cluster containing four six- and three ten-membered silazane rings. This unique silazane cage as well as the other aminosilanes and the silazanes were comprehensively characterised using multi-nuclear solid state and solution NMR, elemental analyses and thermal gravimetry (TGA). PMID:19587990

Wiltzsch, Conny; Wagler, Jörg; Roewer, Gerhard; Kroke, Edwin

2009-07-28

423

Thermally stable supported metal catalysts and inorganic membranes prepared by sol-gel processing  

NASA Astrophysics Data System (ADS)

The application of sol-gel processing to the synthesis of supported metal catalysts, inorganic membranes and catalytic membranes was studied. Noble metals were supported on SiO2 and gamma-Al2O 3. These materials have high surface areas, well-defined pore size distributions, and average pore diameters around 4 nm. The effects of preparative variables such as pH, gelation temperature, metal precursor, metal loading and binder addition on the final properties of the materials were studied. The structure of the sol-gel derived support materials was used to stabilize the dispersion of the supported metal at elevated temperatures and enhance activity and selectivity of the catalyst. The thermal stability of a sol-gel Rh/SiO2 catalyst was tested at 650°C in flowing O2 and compared to the stability of a similar sample prepared by the traditional method of ion-exchange. The ion-exchanged sample had an average pore diameter of 24 nm. The metal particle size distribution of the sol-gel catalyst was more stable due to the smaller pore diameter of that catalyst. The sol-gel samples were more active in the dehydrogenation of n-butane than the ion-exchanged sample. A similar effect of pore size was found for Pd/gamma-Al2O3 catalysts sintered in H 2 at 650°C. The Pd/gamma-Al2O3 catalysts were found to be very active hydrogenation catalysts but were not selective to partially hydrogenated products. A boehmite sol was used as a coating on a porous alpha-Al 2O3 substrate to form a gamma-Al2O3 membrane that could act as a diffusion barrier for gases. A catalytic membrane was formed by adding a soluble palladium compound to the sol. The Pd/gamma-Al 2O3 membrane was used successfully in the selective hydrogenation reactions of acetylene and 1,3-butadiene to produce ethylene and butenes. This was accomplished by premixing the alkyne or diene with H2 and passing it through the membrane wall, therefore reducing the contact time between the reactants and the catalyst.

Lambert, Christine Kay

424

Solid oxide fuel cells developed by the sol-gel process for oxygen generation  

NASA Astrophysics Data System (ADS)

Electrochemical fuel cells convert chemical energy directly to electrical energy through the reaction of a fuel and an oxidant. Solid oxide fuel cells (SOFC) are solid-state devices that operate at temperatures around 800°C, using a solid oxygen electrolyte. The goal of this thesis is to prepare a defect-free solid oxygen electrolyte by a sol-gel process that is capable of (a) functioning in a fuel cell; and (b) producing measurable oxygen when operated as an oxygen generator. Sol-gel processing was chosen for membrane development because it offers a means of applying high-purity layers with controlled doping and a variety of geometries. In this study, the sol-gel process was used to produce yttria-stabilized zirconia (YSZ) electrolyte membranes as well as the electrodes required for an operational fuel cell. Zirconium oxychloride (ZOC) was used as the precursor material for the electrolyte. The YSZ solution was prepared by mixing yttrium nitrate and ZOC in a 50/50 ETOH and water solvent. The reaction was catalyzed with 1.5M NH4OH. Viscosity and solution application techniques were varied to monitor the effect on membrane development. The YSZ layer was sintered to full density. The sol-gel process was used to synthesize supported lanthanum strontium manganate (LSM) electrodes separated by a YSZ electrolyte. The LSM solution was made by mixing strontium nitrate, lanthanum chloride, and manganese acetate solutions. The LSM layers were sintered but were porous. After the membranes were assembled by successive layering and sintering, the membranes and completed fuel cells were characterized using TGA, XRD, FE-SEM, a gas pressurization technique, and electrochemical testing. The YSZ membrane exhibited a stable tetragonal crystal phase and formed a triple phase boundary (TPB) with the cathode. The three phases are the electrode, the electrolyte, and air. Electrochemical testing showed successful membrane development. Although oxygen production was not measured quantitatively, voltage was produced during hydrogen testing. A maximum voltage of 0.352V was obtained using forming gas as a fuel. The relationship between the TPB and oxygen production is critical. By using the sol-gel process, it is possible to form a TPB where the YSZ electrolyte is dense.

Finch, Joshua S.

425

Sol-gel processing of PZT thin films: A review of the state-of-the-art and process optimization strategies  

Microsoft Academic Search

Sol-gel processing has been widely employed for the fabrication of lead zirconate titanate (PZT) thin films. To successfully optimize thin film material properties for different applications, we must develop a fundamental understanding of the processing-property relationships inherent in the sol-gel fabrication process. In the asprepared state, sol-gel thin films are amorphous, have large organic contents, and can possess significant porosity.

Robert W. Schwartz; Timothy J. Boyle; Steven J. Lockwood; Michael B. Sinclair; Duane Dimos; Catherine D. Buchheit

1995-01-01

426

Sol–gel coated polydimethylsiloxane\\/?-cyclodextrin as novel stationary phase for stir bar sorptive extraction and its application to analysis of estrogens and bisphenol A  

Microsoft Academic Search

A sol–gel technique was used for the preparation of a stir bar coated with a composite composed of polydimethysiloxane and ?-cyclodextrin (PDMS\\/?-CD). The sol–gel mechanism during coating procedure was discussed and successful binding of ?-CD to the sol–gel network was confirmed by the IR spectra. Scanning electron micrographs of the stir bars revealed a homogeneous surface with a film thickness

Yuling Hu; Yanjie Zheng; Fei Zhu; Gongke Li

2007-01-01

427

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material  

DOEpatents

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties. 6 figs.

Panitz, J.K.; Reed, S.T.; Ashley, C.S.; Neiser, R.A.; Moffatt, W.C.

1999-07-20

428

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material  

DOEpatents

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

Panitz, Janda K. (Sandia Park, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Moffatt, William C. (Albuquerque, NM)

1999-01-01

429

One- and three-dimensional growth of hydroxyapatite nanowires during sol-gel-hydrothermal synthesis.  

PubMed

Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol-gel-hydrothermal process. Sol-gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol-gel-hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10-50 wt %) were mixed with poly(?-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young's and compressive moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA producing a 3-fold increase in Young's modulus from 193 to 665 MPa and 2-fold increase in compressive modulus from 230 to 487 MPa. These HA nanowires can be used to reinforce polymer composites and are excellent biomaterials for tissue engineering of bone. PMID:22296410

Costa, Daniel O; Dixon, S Jeffrey; Rizkalla, Amin S

2012-03-01

430

Effect of UV-irradiation on sol-gel optical films  

NASA Astrophysics Data System (ADS)

Sol-Gel optical film was widely used in high power laser system with the development of its preparation technique. Ultraviolet treating is an effective method to solidify the film and improve its performance. In this paper, optical films were deposited on K9, silica glass and silicon wafer substrates by Sol-Gel spin-coating method and ultraviolet light source was produced by 1000W high-pressure mercury lamp to irradiate these optical films. SEM, AFM, IR and ellipsometer were used to characterize the structure and optical properties of the films. Mechanical property of films was measured by pencil hardness-testing device. Laser damage threshold of films was measured by a Q-switched Nd:YAG high power laser whose wavelength was 1064nm and its pulse width 15ns. The results show that UV-irradiation can improve the mechanical property and increase the refractive index of the films. The nodules on the film surface can be changed into pits by UV-irradiation process so the laser damage threshold of Sol-Gel thin films increased. The laser damage threshold of ZrO II single-layer film added with PVP reaches 50.6J/cm2 (1064 nm, 1 ns) after UV-irradiation process. It was found that UV-irradiation is an effective method to avoid infiltrating between the layers and improve the homogeneity of the multilayer films. The reflection of 5 layers of ZrO II/SiO II multi-layer films is increased more than 10% after UV-irradiation treatment.

Yang, Fan; Shen, Jun; Sun, Qi; Zhou, Bin; Wu, Guangming; Mugnier, Jacques

2006-01-01

431

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: dissolution behaviour and biological properties after crystallisation.  

PubMed

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol-gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol-gels. After heating and powdering the sol-gels, dissolution behaviour was assessed using ion chromatography to measure Ca(2+) and PO4 (3-) ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue™ assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol-gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol-gel is fired. PMID:24052344

Tredwin, Christopher J; Young, Anne M; Abou Neel, Ensanya A; Georgiou, George; Knowles, Jonathan C

2014-01-01

432

Effects of annealing temperature on the performance of the Schottky diode fabricated with TiO2 sol-gel  

NASA Astrophysics Data System (ADS)

Various conbinations of TiO2 sol-gel were prepared to fabricate Schottky diodes. Pure TiO2 sol-gel was spin-coated to the various substrates such as glass, silicon wafer, and cellulose. The sol-gel driven TiO2 films were generated cracks all over the surface during the annealing process. To prevent cracks, polyethylene glycol (PEG) was added to TiO2 sol-gel solution. TiO2-PEG sol-gel was spin-coated to the substrate and heat treated at 100, 200, and 300°C for 1 h. The film thicknesses were 230, 190, and 129 nm for the sample heated at 100, 200, and 300°C, respectively, and no cracks were observed. The FTIR pesk at 3380 cm-1 corresponds to -OH stretching mode and disappeared as the heating temperature increased. The characteristic peaks of PEG at 2875 and 1120 cm-1 also disappeared as the heating temperature increased. The Schottky diodes comprised of Al/PEG-TiO2/Au with various heat treatment were fabricated. The forward current was drastically increased as the annealing temperature increased. The plots of parabolic conduction curves based on Schottky conduction model, Poole-Frenkel conduction model, and space charge limitted conduction model show nonlinear relationship. These nonlinear relationship indicates that the conduction mechanism is not purely single conduction mechanism.

Chen, Y.; Yoo, K. H.; Kang, K. S.; Kim, Jaehwan

2009-03-01

433

Sol-gel entrapped Candida antarctica lipase B--a biocatalyst with excellent stability for kinetic resolution of secondary alcohols.  

PubMed

Sol-gel entrapment is an efficient immobilization technique that allows preparation of robust and highly stable biocatalysts. Lipase from Candida antarctica B was immobilized by sol-gel entrapment and by sol-gel entrapment combined with adsorption on Celite 545, using a ternary silane precursor system. After optimization of the immobilization protocol, the best enzyme loading was 17.4 mg/g support for sol-gel entrapped lipase and 10.7 mg/g support for samples obtained by entrapment and adsorption. Sol-gel immobilized enzymes showed excellent values of enantiomeric ratio E and activity when ionic liquid 1-octyl-3-methyl-imidazolium tetrafluoroborate was used as additive. Immobilization increased the stability of the obtained biocatalysts in several organic solvents. Excellent operational stability was obtained for the immobilized lipase, maintaining unaltered catalytic activity and enantioselectivity during 15 reuse cycles. The biocatalysts were characterized using scanning electron microscopy (SEM) and fluorescence microscopy. The improved catalytic efficiency of entrapped lipases recommends their application for large-scale kinetic resolution of optically active secondary alcohols. PMID:23124473

Ursoiu, Anca; Paul, Cristina; Kurtán, Tibor; Péter, Francisc

2012-01-01

434

Sol-gel nanocrystalline ZnO:Ag films: Structural and optical properties  

NASA Astrophysics Data System (ADS)

The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The films are obtained by spin coating method on quartz and Si substrates. The effect of the annealing temperatures (500-800 °C) and the gas ambient (oxygen and nitrogen) has been studied by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). Optical properties are investigated by UV-VIS spectroscopy. The transmittance spectra of ZnO:Ag films are differed from ZnO spectra and manifest absorption features due to silver nanoparticles formation.

Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

2014-06-01

435

Tunable Bragg stacks from sol-gel derived Ta2O5 and MEL zeolite films  

NASA Astrophysics Data System (ADS)

In this paper we investigated sol-gel derived Ta2O5 and nanosized MEL zeolite films obtained by spin coating of Tantalum sol and colloidal zeolite solution, respectively. Refractive index and thickness of the films were determined using non-linear curve fitting of measured reflectance spectra. The influence of the post deposition annealing on the optical properties and thickness of the films was studied. Besides tunable Bragg stacks were designed and prepared by layer-by-layer deposition of Ta2O5 and MEL suspensions with quarter-wave thicknesses. The influence of water, acetone and methanol on the optical behavior of Bragg stacks was discussed.

Gospodinov, B.; Dikova, J.; Mintova, S.; Babeva, T.

2012-12-01

436

Optical properties of Cd1-xZnxS nanocrystallites in sol-gel silica matrix  

NASA Astrophysics Data System (ADS)

Cd1-xZnxS nanoparticles with different compositions (0?x?1) embedded in silica matrix were prepared in thin film form by the sol-gel technique. The film texture and structural transformation with increasing x value were studied from transmission electron micrographs and electron diffraction patterns. Optical study indicated increase in optical bandgap and decrease in refractive index with increasing zinc content (x value). Photoluminescence studies showed emission from surface states with emission energy blue shifted with increasing zinc content in the films. Annealing behaviour of the films with increasing annealing temperature and time was studied.

Bhattacharjee, B.; Mandal, S. K.; Chakrabarti, K.; Ganguli, D.; Chaudhuri, S.

2002-10-01

437

Fabrication of silica glass containing yellow oxynitride phosphor by the sol-gel process  

NASA Astrophysics Data System (ADS)

We have prepared silica glass by the sol-gel method and studied its ability to disperse the Ca-?-SiAlON:Eu2+ phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON.

Segawa, Hiroyo; Yoshimizu, Hisato; Hirosaki, Naoto; Inoue, Satoru

2011-06-01

438

Electrochemistry of Prussian Blue in silica sol-gel electrolytes doped with polyamidoamine dendrimers  

Microsoft Academic Search

.   The inclusion of a generation-4 polyamidoamine (G4-PAMAM) dendrimer in a silica sol-gel yielded a solid electrolyte that\\u000a was used to encapsulate Prussian Blue (PB), iron(III) hexacyanoferrate(II), and cobalt hexacyanoferrate. The PB was synthesized\\u000a in the doped silica by sequential immersion of a monolith in 0.1 M K4Fe(CN)6, water, and 0.1 M FeCl3. Inclusion of G4-PAMAM resulted in a nanoporous anion-exchange material

Silvia Zamponi; Anna M. Kijak; André J. Sommer; Roberto Marassi; Pawel J. Kulesza; James A. Cox

2002-01-01

439

Molecular-level engineering of protein physical hydrogels for predictive sol-gel phase behavior  

PubMed Central

Predictable tuning of bulk mechanics from the molecular level remains elusive in many physical hydrogel systems due to the reliance on non-specific and non-stoichiometric chain interactions for network formation. We describe a Mixing-Induced Two-Component Hydrogel (MITCH) system, in which network assembly is driven by specific and stoichiometric peptide-peptide binding interactions. By integrating protein science methodologies with simple polymer physics model, we manipulate the polypeptide binding interactions and demonstrate the direct ability to predict the resulting effects on network crosslinking density, sol-gel phase behavior, and gel mechanics. PMID:21861461

Mulyasasmita, Widya; Lee, Ji Seok; Heilshorn, Sarah C.

2011-01-01

440

Sol–gel synthesis of vanadium pentoxide nanoparticles in air- and water-stable ionic liquids  

Microsoft Academic Search

Vanadium pentoxide (V2O5) nanoparticles were synthesized at moderate reaction temperatures by hydrolysis of VO[OCH(CH3)2]3 in two different air- and water-stable ionic liquids with the same anion: 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)amide\\u000a ([Py1,4]Tf2N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIM]Tf2N) via the sol–gel method using acetone and isopropanol either as refluxing solvents or as co-solvents. The cation type of\\u000a the ionic liquid affects the crystallinity, morphology,

Mohammad Al Zoubi; Hala K. Farag; Frank Endres

2009-01-01

441

Charge transfer induced magnetism in sol-gel derived nanocrystalline BaTiO3  

NASA Astrophysics Data System (ADS)

Nanocrystalline BaTiO3 is prepared by sol-gel synthesis. The charge transfer and different state mixing effects are used in explaining the observed magnetism by the modified Stoner theory. The magnetic coercivity is found to decrease from 125 to 43 Oe as temperature increases from 5 K to 300 K. The optical absorption shows band narrowing arising from exchange-correlation and many-body effects of free carriers created on the surface of nanoparticles, as supported also by the non-adiabatic small polaron conductivity derived from impedance spectroscopy.

Ramakanth, S.; James Raju, K. C.

2014-06-01

442

Characterization of supported alumina membranes formed by an in situ sol-gel method  

SciTech Connect

The formation of alumina coatings on porous ceramic tubes by an in situ sol-gel process was reported earlier. Using this process, coating layers were prepared and heat-treated to temperatures between 60 and 950 C. The bayerite phase of alumina was identified by X-ray diffraction analysis in the dried layers. Gas flow rates of He, N{sub 2}, Ar, and CO{sub 2} were measured. The gas flow rates decreased for a given pressure drop in the order He > N{sub 2} > Ar. CO{sub 2} showed anomalous behavior because of its interaction with the alumina membrane.

Yu, C.C.; Klein, L.C. [Rutgers-The State Univ. of New Jersey, Piscataway, NJ (United States). Ceramics Dept.

1995-11-01

443

Sol-gel strategies for amorphous, inorganic membranes exhibiting molecular sieving characteristics  

SciTech Connect

Sol-gel strategies for the preparation of inorganic membranes involve the deposition of an inorganic sol on a mesoprous support by a process combining the features of slip-casting and dip-coating. In order to be practical the deposited membrane must exhibit both high flux and high selectivity. For porous membranes these requirements are met by extremely thin, porous films exhibiting a narrow size distribution of very small pores. This paper considers the use of polymeric silica and hybrid-organosilyl precursor sols in the context of the underlying physics and chemistry of the membrane deposition process.

Brinker, C.J. [Sandia National Labs., Albuquerque, NM (United States); [Univ. of New Mexico, Albuquerque, NM (United States); Sehgal, R.; Raman, N.K. [Univ. of New Mexico, Albuquerque, NM (United States)] [and others

1994-12-31

444

Synthesis of Nd:YVO{sub 4} thin films by a sol-gel method  

SciTech Connect

Nd:YVO{sub 4} powders and thin films were successfully synthesized by the sol-gel method using metal alkoxides. A homogeneous and stable solution was prepared by the reaction of Y(OEt){sub 3}, VO(OiPr){sub 3}, and Nd(OEt){sub 3} in 2-methoxyethanol. The precursor was a mixture of vanadium and yttrium double alkoxide. Precursor films were prepared by dip coating and crystallization to single-phase YVO{sub 4} at 500 C. Nd:YVO{sub 4} films were crystallized with (200) preferred orientation on glass substrates, which showed the characteristic optical absorption of neodymium.

Hirano, Shinichi; Yogo, Toshinobu; Kikuta, Koichi; Sakamoto, Wataru; Koganei, Hirosada [Nagoya Univ. (Japan)

1996-12-01

445

Sol-gel auto-combustion synthesis of spinel-type ferrite nanomaterials  

NASA Astrophysics Data System (ADS)

Recent developments and trends of sol-gel auto-combustion method for spinel ferrite nanomaterial synthesis are briefly discussed and critically analyzed. The analysis of various parameters of reaction which could be used for better understanding of synthesis process and control of microstructure and property of spinel ferrite nanopowder products was the main objective of this review article. Special attention was paid to variety of particle size and phase purity. For these purposes the correlation between complexant, oxygen balance and combustion process chemical additives, as well as heating mechanism and atmosphere, was established. These results are relevant from standpoints of both application and processing of ferrites.

Sutka, Andris; Mezinskis, Gundars

2012-06-01

446

Nanostructured magnetite (Fe 3O 4) thin films prepared by sol-gel method  

NASA Astrophysics Data System (ADS)

Nanostructured magnetite (Fe 3O 4) thin films have been prepared by a sol-gel method heated at 300°C. The film with a black appearance is homogeneous without cracks by adding N, N-dimethyl formamide (DMF) as drying chemical control agent (DCCA). The root mean square roughness of the thin film is only 2 nm, and the nanograins show a narrow size distribution with an average size of 12.5 nm. The magneto-optical Kerr effect (MOKE), measured in the applied field range from 0 to 1.9 T, reveals that the film exhibits superparamagnetism.

Tang, N. J.; Zhong, W.; Jiang, H. Y.; Wu, X. L.; Liu, W.; Du, Y. W.

2004-11-01

447

Optical Spectroscopy of Hybrid Sol-Gel Coatings Doped with Noble Metals  

Microsoft Academic Search

Sol-gel coatings in the xM· (100-x) SiO2 system, (M = Cu, Ag and Au) x =0.1–10 mol%), are deposited on soda lime glass slides by using silicon tetramethoxide Si(OCH3)4) and methyltriethoxysilane (SiCH3[OCH2CH3]3) as silica precursors. Anhydrous CuCl, CuCl2 · 2H2O, Cu(NO3)2 · 3H2O, CuSO4 · 5H2O, AgNO3 and HAuCl4 · 3H2O are used as copper, silver and gold sources. Coatings

M. A. Villegas; M. A. García; J. Llopis; J. M. Fernández Navarro

1998-01-01

448

TEM-characterization of metallic nanoparticles embedded in sol-gel produced glass-like layers  

SciTech Connect

Size and shape of metallic nanoparticles, which are embedded in sol-gel produced glass-like layers, are able to influence the optical properties of coatings on glass. Since the shape of the particles is determined by its crystalline structure, and the structure is modified significantly during the particle growth, the development of both was observed in dependence on the stage of growth applying conventional and high resolution electron microscopy. These investigations carried out on Au and Ag particles have revealed different types of colloidal growth, a real structure often formed by dislocations and twins as well as a relatively high particle mobility.

Werner, U.; Schmitt, M.; Schmidt, H. [Inst. fuer Neue Materialien, Saarbruecken (Germany)

1996-12-31

449

Fast response methane sensor using nanocrystalline zinc oxide thin films derived by sol–gel method  

Microsoft Academic Search

Undoped nanocrystalline n-ZnO thin films were deposited on SiO2-coated p-Si substrates by sol–gel technique to fabricate ZnO-based resistive sensors for methane detection. The resistance change was studied at different temperatures (50, 150, 200, 250, 300 and 350°C) with two different metallic contacts to ZnO, e.g. gold and palladium-silver, in air and in the presence of three different concentrations (0.1, 0.5

P. Bhattacharyya; P. K. Basu; H. Saha; S. Basu

2007-01-01

450

YAG:Ce3+ Nanophosphor Synthesized with the Salted Sol-Gel Method  

SciTech Connect

Nano-phosphors of Y3Al5O12:Ce3+ (YAG:Ce) were synthesized with a novel salted sol-gel method, in which aqueous solution of inorganic salts (yttrium/cerium nitrates) were used along with the metal alkoxide precursor, aluminum sec-butoxide, Al(OC4H9)3. YAG single phase was formed at temperature as low as 800 ?C. Luminescence of YAG:Ce reached the maximum intensity when calcined above 1350C. The SEM image reveals that the grain sizes of the nano-phosphors calcined at 1100 ?C are in a range of 50-150 nm.

D. Jia; C. V. Shaffer; J. E. Weyant; A. Goonewardene; X. Guo; Y. Wang; X. Z. Guo; K. K. Li; Y. K. Zou; W. Jia

2006-05-01

451

Green fluorescent protein-doped sol-gel silica planar waveguide to detect organophosphorus compound  

NASA Astrophysics Data System (ADS)

We report novel living protein-doped planar waveguide, and real-time detection of an organophosphorus compound using a sol-gel silica planar waveguide doped with a green fluorescent protein and an organophosphorus hydrolase on a yeast-cell surface. The waveguide was pumped at 488 nm, and emitted green fluorescence at the far field. The green fluorescent light at 550 nm changed by 50% from the original power 1 min after application of the organophosphorus compound. The results enable the real-time detection of biochemical weapon and insecticide harmful for human body by using an in-line fiber sensor network.

Enami, Y.; Suye, S.

2012-02-01

452

Formation and transformation of ZnTiO 3 prepared by sol–gel process  

Microsoft Academic Search

ZnTiO3 powders with pure hexagonal phase were prepared by the sol–gel process with Zn(NO3)2·6H2O and Ti(OC4H9)4 materials. The thermal behavior and phase transformation of the gels were investigated by the differential scanning calorimetry–thermogravimetry (DSC–TG) analysis, X-ray diffraction (XRD) patterns, Fourier-transforming infrared (FT-IR) spectroscopy, and Raman scattering spectroscopy. The results revealed that pure hexagonal phase of ZnTiO3 could be obtained at

Lei Hou; Yu-Dong Hou; Man-Kang Zhu; Jianlan Tang; Jing-Bing Liu; Hao Wang; Hui Yan

2005-01-01

453

Hydrogen photochromism in V2O5 layers prepared by the sol-gel technology  

NASA Astrophysics Data System (ADS)

Here we report on hydrogen photochromism in V2O5 highly disordered layers, i.e., photochromism that occurs due to hydrogen atoms; the hydrogen being detached under the action of light from organic molecules adsorbed on the oxide surface, whereas the V2O5 layers have been prepared by the sol-gel technology. The comprehensive characterization of the layers has been carried out, as well as the investigation of the parameters influencing their photochromic sensitivity. The high photochromic sensitivity of the V2O5 layers is provided by the surface Grotthuss diffusion of the injected protons.

Wang, Yi; Pan, Lei; Li, Yao; Gavrilyuk, A. I.

2014-09-01

454

Pyroelectric properties of sol–gel derived lithium tantalite thin films  

Microsoft Academic Search

Lithium tantalite (LiTaO3) thin films (?0.5?m) have been successfully deposited on Pt(111)\\/SiO2\\/Si(100) substrates by means of sol–gel spin-coating technology. Figures of merit for infrared detector were studied for the LiTaO3 thin films. There exists high figures of merit Fv of 2.1×10?10Ccm\\/J and Fm of 2.4×10?8Ccm\\/J because of the relative low dielectric constant (?r) of 35 and high pyroelectric coefficient (?)

M. C. Kao; H. Z. Chen; C. M. Wang; Y. C. Chen

2003-01-01

455

Crystallization of sol-gel deposited potassium-tantalate-niobate thin films on platinum  

NASA Astrophysics Data System (ADS)

Potassium tantalate niobate (KTN) ferroelectric thin films prepared by sol-gel processing have been heat treated in conventional furnaces and through rapid thermal annealing (RTA) to investigate crystallization of the films. Various key factors such as time and temperature influencing the crystallization have been identified. A post-deposition RTA at 750 °C in nitrogen for 5 min crystallized the KTN films into pure perovskite while it took two hours to completely crystallize a similar KTN film in conventional ovens. The effect of preheat treatment at lower temperatures, solution chemistry, and the thickness have also been studied. Preliminary ferroelectric properties of some samples are also presented.

Nazeri, Azar

1994-07-01

456

Epitaxial ferroelectric thin films prepared by the Sol-Gel technique  

Microsoft Academic Search

The sol-gel process was used to fabricate epitaxial thin films of crystalline ferroelectric oxides, including KNbO3 film on single crystal substrates of MgO and SrTiO3, LiNbO3 film on LiTaO3 and alternatively multilayer nX(SrTiO3\\/PbTiO3) films on SrTiO3. Fabrication of these epitaxial thin films will be described. The structure of these films has been studied with X-ray, electron diffraction, and high resolution

Yuhuan Xu; Chih-Hsing Cheng; Yudan Lou; John D. Mackenzie

1997-01-01

457

Pyroelectric properties of sol-gel derived lithium tantalite thin films  

Microsoft Academic Search

Lithium tantalite (LiTaO3) thin films (~0.5mum) have been successfully deposited on Pt(111)\\/SiO2\\/Si(100) substrates by means of sol-gel spin-coating technology. Figures of merit for infrared detector were studied for the LiTaO3 thin films. There exists high figures of merit Fv of 2.1×10-10Ccm\\/J and Fm of 2.4×10-8Ccm\\/J because of the relative low dielectric constant (?r) of 35 and high pyroelectric coefficient (gamma)

M. C. Kao; H. Z. Chen; C. M. Wang; Y. C. Chen

2003-01-01

458

Ultraviolet-Laser-Induced Crystallization of Sol-Gel Derived Inorganic Oxide Films  

Microsoft Academic Search

Structural changes stimulated by ultraviolet (UV) laser irradiations of sol-gel derived inorganic oxide films were investigated. Dried gel films of TiO2, Nb2O5, Ta2O5, SrTiO3 and Pb(ZrxTi1-x)O3 (PZT) were found to be crystallized by the laser irradiation. On the other hand, the photo-induced change in gel films of BaTiO3, LiNbO3 and LiTaO3 was not observed although the laser beams were absorbed

Naoko Asakuma; Toshimi Fukui; Mamoru Aizawa; Motoyuki Toki; Hiroaki Imai; Hiroshi Hirashima

2000-01-01

459

Sol-gel preparation and characterization of non-substituted and Sr-substituted lanthanum cobaltates  

Microsoft Academic Search

This paper reports on the results concerning the sol-gel preparation and characterization of Sr-substituted perovskite lanthanum\\u000a cobaltates La1?xSrxCoO3?? (x = 0.0, 0.25, 0.5 and 0.75). The metal ions, generated by dissolving starting materials in diluted acetic acid were complexed\\u000a by 1,2-ethanediol to obtain the precursors for the non-substituted and Sr-substituted LaCoO3. The influence of the synthesis temperature, heating time and

Sigute Cizauskaite; Aivaras Kareiva

2008-01-01

460

Sol–gel preparation and characterization of non-substituted and Sr-substituted gadolinium cobaltates  

Microsoft Academic Search

An aqueous sol–gel chemistry approach for the preparation of Sr-substituted perovskite gadolinium cobaltates Gd1?xSrxCoO3?? (x=0.0, 0.25, 0.5 and 0.75) has been applied. The metal ions, generated by dissolving starting materials in diluted acetic acid were complexed by EDTA to obtain the precursors for non-substituted and Sr-substituted GdCoO3. However, only two single-phase cobaltate samples with x=0.0 and 0.25 have been obtained

S. Cizauskaite; S. Johnsen; J.-E. Jørgensen; A. Kareiva

2011-01-01

461

Processing and characterization of sol–gel fabricated mixed metal aluminates  

Microsoft Academic Search

Nanocrystalline lanthanum aluminate (LaAlO3, LAP) and Sr-substituted LAP ceramics were synthesized by sol–gel processes using mixtures of inorganic salts of the respective elements. The metal ions, generated by dissolving metal nitrates or acetates in acetic acid and\\/or water were complexed by 1,2-ethanediol to obtain the precursor for LAP. The XRD patterns of the LaAlO3 and La1?xSrxAlO3?? (x?0.50) ceramic sintered at

M. Chroma; J. Pinkas; I. Pakutinskiene; A. Beganskiene; A. Kareiva

2005-01-01

462

Nanofibers of barium strontium titanate (BST) by sol–gel processing and electrospinning  

Microsoft Academic Search

This paper describes the fabrication of barium strontium titanate (Ba0.6Sr0.4TiO3 or BST) nanofibers by electrospinning method using a solution that contained poly(vinylpyrrolidone) and a sol–gel solution of BST. The as-spun and calcined BST\\/PVP composite nanofibers were characterized by TG-DTA, X-ray diffraction, FT-IR, SEM and TEM, respectively. After calcination of the as-spun BST\\/PVP composite nanofibers at above 700?°C in air for

Santi Maensiri; Wiwat Nuansing; Jutharatana Klinkaewnarong; Paveena Laokul; Jinda Khemprasit

2006-01-01

463

Optimization of alkyl ester production from grease using a phyllosilicate sol-gel immobilized lipase.  

PubMed

Simple alkyl ester derivatives of restaurant grease were prepared using a lipase from Pseudomonoas cepacia immobilized within a phyllosilicate sol-gel matrix as biocatalyst. Alcoholysis reactions of grease were carried out in solvent-free media using a one-step addition of alcohol to the reaction mixture. The immobilized lipase was active from 40 to 70 degrees C. Ester yields (60-97%) were highest when using a ratio of reactants of 2 mmol grease to 8 mmol alcohol and the biocatalyst was 10% (w/w) of grease in the presence of molecular sieves. PMID:14626413

Hsu, An-Fei; Jones, Kerby C; Foglia, Thomas A; Marmer, William N

2003-10-01

464

Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites  

DOEpatents

A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.

Guadalupe, Ana R. (San Juan, PR); Guo, Yizhu (San Juan, PR)

2001-05-15

465

Synthesis of sodium titanate composites by sol-gel method for use in gas potentiometric sensors  

Microsoft Academic Search

Mixtures of Na2Ti3O7\\/Na2Ti6O13 and Na2Ti6O13\\/TiO2 were synthesised by the sol-gel method using alkoxide precursors. XRD and SEM characterisations were performed. Semi-quantitative chemical analyses were carried out and the mixture ratio of Na2Ti3O7\\/Na2Ti6O13 was 3:1 wt. A qualitative estimation on the mixture Na2Ti6O13\\/TiO2 gives also a higher ratio. Such composites are well suited to be used directly as oxygen electrode materials

Joel Ram??rez-Salgado; Elisabeth Djurado; Pierre Fabry

2004-01-01

466

The development and characterization of sol-gel substrates for chemical and optical applications  

NASA Astrophysics Data System (ADS)

The sol gel process can be used to make monolithic porous glass for various scientific and engineering uses. The porosity of the material imparts a large surface area which is advantageous in applications such as catalyst supports or in the study of surface mediated chemical reactions. The chemical stability and transparency of the porous glass also make it suitable for use in the emerging field of optical sensors. In this study fluoride catalysis is used to produce sol gel monoliths with pore radii of up to 400 Angstroms, four times larger than any previously reported using conventional drying techniques. Gel monoliths with pore radii of 200 Angstroms were found to have the best combination of surface area, pore volume and optical transparency. Typical monoliths have surface areas of 150 m2/g and pore volumes of 1.60 cm3/g with good transparency. The monoliths are chemically stable, have good mechanical strength and can be easily rehydrated without cracking. The substrates are also suitable for sintering into dense high purity silica glass with little tendency towards foaming. An in-depth study of the catalytic effect of fluoride on the sol gel process is also included. It has been theorized that fluoride serves to expand the coordination sphere of the silicon center making it more subject to nucleophilic attack. In this work an ion-specific fluoride electrode is used to monitor free fluoride concentrations in HF catalyzed sols while silicic acid is added in the form of tetramethoxysilane (TMOS). It is found that fluoride is rapidly bound by the silicic acid in a ratio of four to one, indicating the formation of silicon tetrafluoride. A concurrent decrease in pH suggests that a pentacoordinate species is formed that is more stable than previously thought. A polymerization mechanism is proposed that explains the hydrophobicity of fluoride catalyzed gels and the difficulty in retaining structural fluoride in fluoride catalyzed sol gel glasses. Finally, several porous monoliths are doped with colloidal gold and the optical properties evaluated as a function of heat treatment. This demonstrates the feasibility of using porous glass nanocomposites in sensors and other optical components.

Powers, Kevin William

1998-12-01

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Free volume effects on the fluorescence characteristics of sol-gel glasses doped with quinine sulphate  

NASA Astrophysics Data System (ADS)

The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of quinine sulfate doped sol-gel glasses, before and after PMMA polymer impregnation, are investigated at differe