Note: This page contains sample records for the topic non-aqueous sol-gel route from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Synthesis of cobalt aluminate nanopigments by a non-aqueous sol-gel route.  

PubMed

Here we report the chemical synthesis of cobalt aluminum oxide (CoAl2O4) nanoparticles by a non-aqueous sol-gel route. The one-pot procedure is carried out at mild temperatures (in the 150 to 300 °C range), and consists of the reaction between cobalt acetate and aluminium isopropoxide in benzyl alcohol. The resulting CoAl2O4 nanoparticles show an unusually low average size, between 2.5 and 6.2 nm, which can be controlled by the synthesis temperature. The colorimetric properties of the nanoparticles are also determined by the synthesis temperature and the characteristic blue color of CoAl2O4 pigments is achieved in samples prepared at T ? 200 °C. The nanoparticles are antiferromagnetically ordered below ?27 K with an uncompensated configuration. The uncompensated moment shows the typical features of strongly interacting superparamagnetic nanoparticles and spin-glass systems. PMID:23552361

Karmaoui, Mohamed; Silva, Nuno J O; Amaral, Vitor S; Ibarra, Alfonso; Millán, Ángel; Palacio, Fernando

2013-05-21

2

Synthesis of cobalt aluminate nanopigments by a non-aqueous sol-gel route  

NASA Astrophysics Data System (ADS)

Here we report the chemical synthesis of cobalt aluminum oxide (CoAl2O4) nanoparticles by a non-aqueous sol-gel route. The one-pot procedure is carried out at mild temperatures (in the 150 to 300 °C range), and consists of the reaction between cobalt acetate and aluminium isopropoxide in benzyl alcohol. The resulting CoAl2O4 nanoparticles show an unusually low average size, between 2.5 and 6.2 nm, which can be controlled by the synthesis temperature. The colorimetric properties of the nanoparticles are also determined by the synthesis temperature and the characteristic blue color of CoAl2O4 pigments is achieved in samples prepared at T >= 200 °C. The nanoparticles are antiferromagnetically ordered below ~27 K with an uncompensated configuration. The uncompensated moment shows the typical features of strongly interacting superparamagnetic nanoparticles and spin-glass systems.Here we report the chemical synthesis of cobalt aluminum oxide (CoAl2O4) nanoparticles by a non-aqueous sol-gel route. The one-pot procedure is carried out at mild temperatures (in the 150 to 300 °C range), and consists of the reaction between cobalt acetate and aluminium isopropoxide in benzyl alcohol. The resulting CoAl2O4 nanoparticles show an unusually low average size, between 2.5 and 6.2 nm, which can be controlled by the synthesis temperature. The colorimetric properties of the nanoparticles are also determined by the synthesis temperature and the characteristic blue color of CoAl2O4 pigments is achieved in samples prepared at T >= 200 °C. The nanoparticles are antiferromagnetically ordered below ~27 K with an uncompensated configuration. The uncompensated moment shows the typical features of strongly interacting superparamagnetic nanoparticles and spin-glass systems. Electronic supplementary information (ESI) available: Further microscopy, diffraction, spectroscopy and thermal data. See DOI: 10.1039/c3nr34229h

Karmaoui, Mohamed; Silva, Nuno J. O.; Amaral, Vitor S.; Ibarra, Alfonso; Millán, Ángel; Palacio, Fernando

2013-05-01

3

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

4

Non-hydrolytic sol-gel routes to heterogeneous catalysts.  

PubMed

Oxides and mixed oxides have a tremendous importance in the field of heterogeneous catalysis, serving either as catalysts or as supports for active species. The performance of a catalyst depends directly on its composition, texture, structure and surface properties, which have to be precisely controlled and adapted to each application. In this context, the sol-gel process is a unique tool for the preparation and understanding of catalytic materials, owing to its exceptional versatility. In the last 10 years, the non-hydrolytic sol-gel (NHSG) or non-aqueous sol-gel process based on nonhydrolytic condensations in nonaqueous media has established itself as a simple and powerful method for the design of a wide range of oxide, mixed oxide and hybrid materials with controlled composition, morphology, texture and structure. NHSG proved particularly interesting for the preparation of catalytic materials, notably mesoporous xerogels, single site catalysts and highly crystalline nanoparticles. This critical review addresses the application of NHSG to the preparation of heterogeneous catalysts, emphasizing the specificities of this process, and giving a comprehensive overview of the literature (251 references). PMID:22377899

Debecker, Damien P; Mutin, P Hubert

2012-05-01

5

The fluorolytic sol-gel route to metal fluorides--a versatile process opening a variety of application fields.  

PubMed

The recently developed fluorolytic sol-gel route to metal fluorides opens a very broad range of both scientific and technical applications of the accessible high surface area metal fluorides, many of them have already been applied or tested. Specific chemical properties such as high Lewis acidity and physical properties such as high surface area, meso-porosity and nano-size as well as the possibility to apply metal fluorides on surfaces via a non-aqueous sol make the fluorolytic synthesis route a very versatile one. The scope of its scientific and technical use and the state of the art are presented. PMID:18283370

Rüdiger, Stephan; Kemnitz, Erhard

2008-03-01

6

The effect of the sol–gel route on the characteristics of acid–base sensors  

Microsoft Academic Search

The acid–base indicators alizarin red, brilliant yellow and acridine were encapsulated within a silica matrix by three different sol–gel methods: namely, (1) the non-hydrolytic and the (2) acidic and (3) basic hydrolytic routes. The sensors were characterized by several complementary techniques to investigate the effect of the nature of the sensor and of the sol–gel route on the structural and

Larissa Brentano Capeletti; Francielle Leonardelli Bertotto; João Henrique Zimnoch Dos Santos; Edwin Moncada; Mateus Borba Cardoso

2010-01-01

7

Structural, magnetic and electrical properties of cobalt ferrites prepared by the sol–gel route  

Microsoft Academic Search

Nanosized cobalt ferrites having the general formula CoFe2?xAlxO4 (for x=0.00, 0.25, 0.50) have been synthesized by the sol–gel route. The effect of Al3+ ions on structural, Curie temperature, DC electrical resistivity and dielecltric properties are presented in this paper. From the analysis of powder X-ray diffraction patterns, the nanocrystallite size was calculated by the most intense peak (311) using Scherrer

I. H. Gul; A. Maqsood

2008-01-01

8

Sol–gel thermal barrier coatings: Optimization of the manufacturing route and durability under cyclic oxidation  

Microsoft Academic Search

A new promising and versatile process based on the sol–gel transformation has been developed to deposit yttria-stabilized thermal barrier coatings. The non-oriented microstructure with a randomly structured pore network, resulting from the soft chemical process, is expected to show satisfactory thermo-mechanical behaviour when the TBC is cyclically oxidised. The first stage of the research consists of optimizing the processing route

Julien Sniezewski; Yannick LeMaoult; Philippe Lours; Lisa Pin; Vincent Menvie Bekale; Daniel Monceau; Djar Oquab; Justine Fenech; Florence Ansart; Jean-Pierre Bonino

9

Sol–gel thermal barrier coatings: Optimization of the manufacturing route and durability under cyclic oxidation  

Microsoft Academic Search

A new promising and versatile process based on the sol–gel transformation has been developed to deposit yttria-stabilised thermal barrier coatings. The non-oriented microstructure with randomly structured pore network, resulting from the soft chemical process, is expected to show satisfactory thermo-mechanical behaviour when the TBC is cyclically oxidized. First stage of the research consists of optimizing the processing route to generate

Julien Sniezewski; Yannick LeMaoult; Philippe Lours; Lisa Pin; Vincent Menvie Bekale; Daniel Monceau; Djar Oquab; Justine Fenech; Florence Ansart; Jean-Pierre Bonino

2010-01-01

10

Particle Size Analysis of Barium Titanate Powder by Slow-Rate Sol-Gel Process Route  

Microsoft Academic Search

In this research work, different compositional ratios of barium titanate [BT] powders have been prepared using slow-rate gellification by sol-gel route. The as-prepared materials have been calcinated at 300deg C for 8 hours to remove the presence of carbon, and subsequently annealed at 700deg C for one hour for the phase formation. After annealing, the finely grinded powders were characterized

R. Balachandran; H. K. Yow; M. Jayachandran; W. Y. Wan Yusof; V. Saaminathan

2006-01-01

11

Sol–gel route to synthesize titania-silica nano precursors for photoactive particulates and coatings  

Microsoft Academic Search

Nano titanium dioxide sols containing silica in the range 5–50 mol% have been synthesized using sol–gel route starting from\\u000a titanyl sulphate with a view of developing antisoiling surfaces. The titania sol had an average particle size of ~30 nm while\\u000a the average size of titania-silica sol was 61 nm. The influence of silica addition on the phase transition and grain growth\\u000a of nanocrystalline

V. S. Smitha; K. A. Manjumol; K. V. Baiju; Swapankumar Ghosh; P. Perumal; K. G. K. Warrier

2010-01-01

12

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

13

New sol–gel synthetic route to transition and main-group metal oxide aerogels using inorganic salt precursors  

Microsoft Academic Search

We have developed a new sol–gel route to synthesize several different transition and main-group metal oxide aerogels. The approach is straightforward, inexpensive, versatile, and it produces monolithic microporous materials with high surface areas. Specifically, we report the use of epoxides as gelation agents for the sol–gel synthesis of chromia aerogels and xerogels from simple Cr(III) inorganic salts. The dependence of

Alexander E Gash; Thomas M Tillotson; Joe H Satcher Jr; Lawrence W Hrubesh; Randall L Simpson

2001-01-01

14

Preparation of multicomponent oxides via non-hydrolytic sol gel routes from novel bimetallic alkoxides  

NASA Astrophysics Data System (ADS)

New series of double alkoxides of erbium and its oxides have been prepared by non-hydrolytic sol-gel reactions for the first time. These compounds were characterized with the help of FT-IR, NMR, Mass, DTA-TGA and SEM. The mass spectra show similar types of fragmentation pattern in all compounds. The XRD diffraction pattern shows an enhanced homogeneity at high temperature. TGA/DTA measurements show that thermal decomposition occurs in steps and entirely depends on the chemical compositions and the synthesis routes. The SEM observation reveals a high dense and smooth microstructural uniformity of polycrystalline nature. The physico-chemical properties show that crystallization behaviors can be controlled with the help of fine-tuning the chemical properties of chelating agents in order to increase the solubility of metal alkoxides.

Athar, Taimur; Oh Kwon, Jeong; Seok, Sang Il

2005-05-01

15

Preparation of La sub 2 Zr sub 2 O sub 7 by sol-gel route  

SciTech Connect

The La{sub 2}Zr{sub 2}O{sub 7} phase was prepared from metal acetylacetonates by a sol-gel route without any intermediate phase formation. X-ray peaks appeared at a temperature as low as 500{degrees}C at the positions expected for La{sub 2}Zr{sub 2}O{sub 7}, although they were broad. The crystal structure of La{sub 2}Zr{sub 2}O{sub 7} was found to be of the fluorite type below 900{degrees}C and of the pyrochlore type above 1000{degrees}C. The substitution of a small amount of Eu for La was carried out to investigate the crystal structure from the viewpoint of fluorescence, and these results confirmed the formation of fluorite type La{sub 2}Zr{sub 2}O{sub 7} below 900{degrees}C.

Kido, H.; Komarneni, S.; Roy, R. (Materials Research Lab., Pennsylvania State Univ., University Park, PA (US))

1991-02-01

16

Preparation and characterization of nanometer-sized (Pb 1? x ,Ba x )TiO 3 powders using acetylacetone as a chelating agent in a non-aqueous sol–gel process  

Microsoft Academic Search

Nanometer-sized lead barium titanate (Pb1?xBaxTiO3, PBxT) powders were prepared by a non-aqueous sol–gel process using lead acetate, barium acetate, and titanium isopropoxide as precursors and ethylene glycol as the solvent. In this procedure, Ti-isopropoxide was chelated with acetylacetone. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis\\/differential thermal analysis (TGA\\/DTA), X-ray diffraction (XRD), scanning electron

Hong Zhu; Zhijun Guo; Wein-Duo Yang; Wein-Feng Chang; Cheng-Chin Wang

2011-01-01

17

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

18

A general aqueous sol gel route to Ln2Sn2O7 nanocrystals  

NASA Astrophysics Data System (ADS)

This paper describes a general aqueous sol-gel route for the synthesis of a series of rare earth stannates, Ln2Sn2O7 (Ln = Y, La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu), with pure pyrochlore phase via the assistance of a cetyltrimethyl ammonium bromide (CTAB) surfactant. The route involves first the formation of CTAB-inorganic lamellar structures and then their thermal decomposition at 800 °C to yield the pyrochlore Ln2Sn2O7 nanocrystals. Techniques using a thermo-gravimetric/differential thermal analyzer (TG-DTA), x-ray diffraction (XRD) and transmission electron microscopy (TEM) as well as selected-area electron diffraction (SAED) have been employed to characterize the as-synthesized Ln2Sn2O7 nanocrystals. Furthermore, photoluminescence (PL) of the 5% Eu3+ activated Ln2Sn2O7 nanocrystals and carbon monoxide catalytic oxidation over the as-obtained Ln2Sn2O7 nanocrystals were investigated. The results indicate that the PL properties as well as the catalytic activity changes significantly with the ionic radii of the rare earth elements.

Cheng, Hua; Wang, Liping; Lu, Zhouguang

2008-01-01

19

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.

Martinelli, Anna

2014-01-01

20

Comparative study of potassium hexatitanate (K2Ti6O13) whiskers prepared by sol-gel and solid state reaction routes  

NASA Astrophysics Data System (ADS)

Polycrystalline phases of the potassium hexatitanate (K2Ti6O13) were synthesized by conventional solid state reaction and sol-gel methods with a view to compare structural, electrical, optical and photocatalytic properties. Single phase K2Ti6O13 prepared by sol-gel method (PSG) revealed higher value of dielectric constant than same obtained by the solid state reaction method (PSS), attributed to smaller particle size in sol-gel method. Band gap (3.48 eV) of K2Ti6O13 prepared by sol-gel method was found higher than (3.06 eV), obtained in solid state reaction method. Additionally, K2Ti6O13 was tested as photocatalyst on the degradation of methyl orange (MO) under UV light and found better activity for sample PSG. Morphological characteristic exhibited formation of nanorods in sol-gel route and formation of microrods in solid state reaction method.

Siddiqui, Mohd Asim; Chandel, Vishal Singh; Azam, Ameer

2012-07-01

21

A new synthesis route to high surface area sol gel bioactive glass through alcohol washing  

PubMed Central

Bioactive glass is one of the widely used bone repair material due to its unique properties like osteoconductivity, osteoinductivity and biodegradability. In this study bioactive glass is prepared by the sol gel process and stabilized by a novel method that involves a solvent instead of the conventional calcinations process. This study represents the first attempt to use this method for the stabilization of bioactive glass. The bioactive glass stabilized by this ethanol washing process was characterized for its physicochemical and biomimetic property in comparison with similar composition of calcined bioactive glass. The compositional similarity of the two stabilized glass powders was confirmed by spectroscopic and thermogravimetric analysis. Other physicochemical characterizations together with the cell culture studies with L929 fibroblast cells and bone marrow mesenchymal stem cells proved that the stabilization was achieved with the retention of its inherent bioactive potential. However an increase in the surface area of the glass powder was obtained as a result of this ethanol washing process and this add up to the success of the study. Hence the present study exhibits a promising route for high surface area bioactive glass for increasing biomimicity.

M. Mukundan, Lakshmi; Nirmal, Remya; Vaikkath, Dhanesh; Nair, Prabha D.

2013-01-01

22

Improvements in transmittance, mechanical properties and thermal stability of silica–polyimide composite films by a novel sol–gel route  

Microsoft Academic Search

Sol–gel process has been frequently employed for preparation of silica\\/polyimide composite films. In this article, a novel sol–gel route is introduced to prepare silica (SiO2)\\/polyimide (PI) (PS2 system) composite films and to enhance the compatibility between the polyimide and silica. The transmittance, mechanical properties, thermal stability, and morphology of the PS2 composites are studied and compared with the PS1 films

Yan Li; Shao-Yun Fu; Yuan-Qing Li; Qin-Yan Pan; Guanshui Xu; Chee-Yoon Yue

2007-01-01

23

Erbium and ytterbium co-doped SiO 2 :GeO 2 planar waveguide prepared by the sol–gel route using an alternative precursor  

Microsoft Academic Search

The sol–gel method combined with a spin-coating technique has been successfully applied for the preparation of rare-earth\\u000a doped silica:germania films used for the fabrication of erbium-doped waveguide amplifiers (EDWA), presenting several advantages\\u000a over other methods for the preparation of thin films. As with other methods, the sol–gel route also shows some drawbacks,\\u000a such as cracks related to the thickness of

Fernando A. Sigoli; Younes Messaddeq; Sidney J. L. Ribeiro

2008-01-01

24

Preparation of titanium dioxide films by sol-gel route for gas sensors  

NASA Astrophysics Data System (ADS)

Semiconductor oxides such as SnO2, TiO2, WO3, ZnO2 etc. have been shown to be useful as gas sensor materials for monitoring various pollutant gases like H2S, NOx, NH3 etc. In this work, we would like to present the preparation of titanium dioxide films for gas sensor application, via the sol-gel technique. The coating solution was prepared by using titanium isopropoxide precursor, which was hydrolyzed with distilled water under the catalytic effect of different acids (HNO3, HCl or CH3COOH). Titanium dioxide films have been deposited using spin coating method and then synthesized at different temperatures. Fourier transform infrared spectroscopy observation has been used to analyze the sol-gel process. The morphology and the structure of the thin films were analyzed.

Schiopu, Vasilica; Matei, Alina; Cernica, Ileana; Podaru, Cecilia

2009-01-01

25

Sol-Gel Route to Porous Lanthanum Cobaltite (LaCoO3) Thin Films  

Microsoft Academic Search

Sol- gel-derived LaCoO3 thin films were deposited on yttria- stabilized zirconia (YSZ) substrates from a lanthanum iso- propoxide- cobalt acetate (with 2-methoxyethanol) precursor solution. A chelating agent (2-ethylacetoacetate) and polyeth- ylene glycol (PEG) were used to modify the above-mentioned precursor solution. The La-Co precursor solution was suffi- ciently viscous, and transparent LaCoO3 gel films were pre- pared successfully using a

Hae Jin Hwang; Jooho Moon; Masanobu Awano; Kunihiko Maeda

2004-01-01

26

Preparation of Inorganic Oxides via a Non-Hydrolytic Sol-Gel Route  

Microsoft Academic Search

Inorganic oxides have been synthesized successfully under mild reaction conditions using a solvent-free non-hydrolytic sol-gel process based on the condensation reaction of “metal” chlorides with oxygen donors such as alkoxides, aldehydes and ethers. Iron(III) chloride was found to be an effective catalyst for the reactions. The order of reactivity of the halides was generally titanium > aluminium > silicon, but

John N. Hay; Hema M. Raval

1998-01-01

27

Preparation of titanium dioxide films by sol-gel route for gas sensors  

Microsoft Academic Search

Semiconductor oxides such as SnO2, TiO2, WO3, ZnO2 etc. have been shown to be useful as gas sensor materials for monitoring various pollutant gases like H2S, NOx, NH3 etc. In this work, we would like to present the preparation of titanium dioxide films for gas sensor application, via the sol-gel technique. The coating solution was prepared by using titanium isopropoxide

Vasilica Schiopu; Alina Matei; Ileana Cernica; Cecilia Podaru

2009-01-01

28

Deposition of Ferroelectric BST Thin Films by Sol Gel Route in View of Electronic Applications  

Microsoft Academic Search

We report on the deposition of Ba 0.7 Sr 0.3 TiO 3 thin films, BST (70\\/30), by a sol-gel process. After deposition by spin coating, the film is annealed at 750°C, one hour in air. BST films have been deposited on (111) silicon substrates (bare and platinum coated) and on (0001) sapphire. X-Ray diffration patterns show that the films are

G. Velu; J. C. Carru; E. Cattan; D. Remiens; X. Melique; D. Lippens

2003-01-01

29

Ferroelectric properties of tungsten-doped bismuth titanate thin film prepared by sol–gel route  

Microsoft Academic Search

Ferroelectric properties of W-doped Bi4Ti3O12 (W-BIT) thin film were investigated in comparison with those of undoped Bi4Ti3O12 (BIT), which were prepared by sol–gel method and spin-coating technique. X-ray diffraction (XRD) measurements showed layered perovskite structures with a single phase in both films. The W-BIT film appeared to have superior ferroelectric properties to the undoped film prepared under the same conditions.

Jong Kuk Kim; Tae Keon Song; Sang Su Kim; Jinheung Kim

2002-01-01

30

A sol gel route for the development of rare-earth aluminum borate nanopowders and transparent thin films  

NASA Astrophysics Data System (ADS)

A new sol-gel route was applied to obtain Y 0.9Er 0.1Al 3(BO 3) 4 crystalline powders and amorphous thin films by using Al(acac) 3, B(OPr i) 3, Y(NO 3) 3·6H 2O, and Er(NO 3) 3·5H 2O as starting materials dissolved in propionic acid and ethyl alcohol mixtures. Our study shows that propionic acid acts as good chelant agent for yttrium and erbium ions while ethyl alcohol allows to dissolve Al(acac) 3. This process makes the resulting sols very stable to obtain homogeneous gels and transparent amorphous thin films. In addition, the propionic acid prevents the sol precipitation, making easy porous- and crack-free thin film depositions. Chemical reactions involved in the complexation were discussed. As-prepared powders and films are amorphous and present a good thermal stability due to their high glass transition (746 °C) and crystallization temperatures (830 °C). This new sol-gel route showed to be adequate to obtain dense and crack-free thin films free of organic and hydroxyl groups that can be considered as promising materials to be used in integrated optical systems.

Maia, Lauro J. Q.; Mastelaro, Valmor R.; Pairis, Sebastien; Hernandes, Antonio C.; Ibanez, Alain

2007-02-01

31

New Sol-Gel Route for Processing of PMN Thin Films  

Microsoft Academic Search

Pyrochlore free Pb(Mg1\\/3Nb2\\/3)O3 (PMN) thin films were prepared from mixed-metal precursors solutions using the sol-gel process. Lead acetate [Pb(CH3COO)2], magnesium acetate [Mg(CH3COO)2] and niobium ethoxide [Nb(C2H5O)5] were used as starting materials, while 2-isopropoxy-ethanol was chosen as solvent. The reactivity of the precursors was investigated in order to understand and control the process and thus to prevent the contamination of the

Stephane Parola; Roland Khem; David Cornu; Zian Kighelman; Dragan Damjanovic; Nava Setter

2003-01-01

32

Effect of the sol-gel route on the textural characteristics of silica imprinted with Rhodamine B.  

PubMed

A series of silica xerogels that support Rhodamine B as a template were synthesized using distinct sol-gel routes, namely, acid-catalyzed routes, a base-catalyzed route, acid-catalyzed with base-catalyzed (two steps) hydrolytic routes, and a FeCl3 -catalyzed nonhydrolytic route. The extraction methods (thermal, Soxhlet, water washing, and ultrasound) were also evaluated. The resulting xerogels were characterized through porosimetry using nitrogen adsorption/desorption. The samples were further analyzed through small-angle X-ray scattering, Fourier transform infrared spectroscopy, and SEM. The preparation route affected the materials' textural properties. Extraction was optimized using acid and two-step routes. The acid route from Rhodamine B to Rhodamine 6G generated the highest selectivity factor (2.5). The nonhydrolytic route produced the best imprinting factor. Competitive adsorption was also used, from which the approximate imprinting factor was 2. The cavity shape generated during the production of the imprinted silica dictates the adsorption behavior, not the magnitude of the surface area. PMID:24478149

de Coelho Escobar, Cícero; dos Santos, João Henrique Zimnoch

2014-04-01

33

New sol-gel synthetic route to transition and main-group metal oxide aerogels using inorganic salt precursors  

SciTech Connect

We have developed a new sol-gel route to synthesize several transition and main-group metal oxide aerogels. The approach is straightforward, inexpensive, versatile, and it produces monolithic microporous materials with high surface areas. Specifically, we report the use of epoxides as gelation agents for the sol-gel synthesis of chromia aerogels and xerogels from simple Cr(III) inorganic salts. The dependence of both gel formation and its rate was studied by varying the solvent used, the Cr(III) precursor salt, the epoxide/Cr(III) ratio, as well as the type of epoxide employed. All of these variables were shown to affect the rate of gel formation and provide a convenient control of this parameter. Dried chromia aerogels were characterized by high-resolution transmission electron microscopy (HRTEM) and nitrogen adsorption/desorption analyses, results of which will be presented. Our studies have shown that rigid monolithic gels can be prepared from many different metal ions salts, provided the formal oxidation state of the metal ion is greater than or equal to +3. Conversely, when di-valent transition metal salts are used precipitated solids are the products.

Gash, A E; Tillotson, T M; Satcher Jr, J H; Hrubesh, L W; Simpson, R L

2000-09-12

34

Magnetism and phase transformation of Cu-Fe composite oxides prepared by the sol-gel route  

NASA Astrophysics Data System (ADS)

The Cu-Fe composite oxides were prepared by an epoxide assisted sol-gel route. The structural and magnetic properties of Cu-Fe composite oxides calcinated at different temperatures were determined by X-ray diffraction (XRD), Mössbauer spectroscopy measurements, and magnetic measurements. These results indicated that CuFe2O4 was only formed as calcination temperature increased to 500 °C, and a crystalline phase transformation from c-CuFe2O4 to t-CuFe2O4 occurred in elevating calcination temperature above it. All Cu-Fe oxides had ferromagnetic nature, and the significant superparamagnetic behavior was observed in the results of magnetic and Mössbauer spectroscopy measurements.

Xiao, Z. H.; Jin, S. H.; Wang, J. H.; Liang, C. H.

2013-04-01

35

Thermo-optic characterization of neodymium/nickel doped silica glasses prepared via sol-gel route  

NASA Astrophysics Data System (ADS)

Intrinsic as well as rare earth (Neodymium) doped silica glasses with various molar ratio of dopant and a metallic (Nickel) co-dopant is prepared via sol-gel route. The structural characterization of the sample is carried out using X-ray diffraction and Fourier Transform Infrared Spectroscopy. The influence of dopant and doping concentration on the optical properties of silica matrix is investigated via UV-VIS absorption spectroscopy. Effect of dopant on thermal effusivity value of the host matrix is carried out by laser induced open cell photoacoustic technique. Analysis of the results showed that doping affect the thermal effusivity value and results are interpreted in terms of structural modification of the lattice and phonon assisted heat transport mechanism.

Manuel, Ancy; Rajesh Kumar, B.; Shemeena Basheer, N.; Syamala Kumari, B.; Paulose, P. I.; Kurian, Achamma; George, Sajan D.

2012-12-01

36

Thermo-optic characterization of neodymium/nickel doped silica glasses prepared via sol-gel route.  

PubMed

Intrinsic as well as rare earth (Neodymium) doped silica glasses with various molar ratio of dopant and a metallic (Nickel) co-dopant is prepared via sol-gel route. The structural characterization of the sample is carried out using X-ray diffraction and Fourier Transform Infrared Spectroscopy. The influence of dopant and doping concentration on the optical properties of silica matrix is investigated via UV-VIS absorption spectroscopy. Effect of dopant on thermal effusivity value of the host matrix is carried out by laser induced open cell photoacoustic technique. Analysis of the results showed that doping affect the thermal effusivity value and results are interpreted in terms of structural modification of the lattice and phonon assisted heat transport mechanism. PMID:23021845

Manuel, Ancy; Kumar, B Rajesh; Basheer, N Shemeena; Kumari, B Syamala; Paulose, P I; Kurian, Achamma; George, Sajan D

2012-12-01

37

Luminescent properties and the morphology of SrMoO4:Eu3+ powders synthesized via combining sol-gel and solid-state route  

NASA Astrophysics Data System (ADS)

SrMoO4:Eu3+ red phosphors were prepared by combining sol-gel and solid-state route. Citric acid and ethylenediaminetetraacetic acid (EDTA), employed as the chelating agents, were added to the aqueous solutions of metal nitrates. X-ray diffraction (XRD) and photoluminescent spectra techniques (PL) were used to characterize the resultant powders. The results indicated the obtained SrMoO4:Eu3+ phosphors were fine powders with a particle size of 50 nm. The effects of synthesizing conditions were also investigated and optimized, which included the synthesis temperature and the activator concentration on the luminescent intensity. Compared with SrMoO4:Eu3+ phosphors prepared by Solid-state reaction SrMoO4:Eu3+ phosphors prepared by combining sol-gel and solid-state route showed appropriate particle size and a higher emission intensity.

Wei, Qiong; Chen, Donghua

2010-10-01

38

Characterizations of mixed Bi\\/V oxide films, deposited via sol–gel route, used as electrodes in asymmetric liquid crystal cells  

Microsoft Academic Search

In the search of new materials for electrodes in electrochromic devices and in asymmetric liquid crystal cells, some modified vanadium oxide thin films has been investigated. The new gels have been generated by the addition of 10% of bismuth (atomic ratio) to the precursors mixture. The sol–gel route started from metal alkoxides, vanadium oxo iso-propoxide and BiCl3 dissolved in ethanol

E. Cazzanelli; S. Marino; V. Bruno; M. Castriota; N. Scaramuzza; G. Strangi; C. Versace; R. Ceccato; G. Carturan

2003-01-01

39

Characterization of spinel Co 3O 4 and Li-doped Co 3O 4 thin film electrocatalysts prepared by the sol–gel route  

Microsoft Academic Search

Spinel Co3O4 and Li-doped Co3O4 thin film electrocatalysts deposited on Pt and ITO\\/glass substrates were prepared by the sol–gel route from Co(II) sulfate precursor using dip-coating technique. Stoichiometry of undoped and Li+ doped films (up to 10 mol% of Li+) prepared at 300 and 500°C, respectively, showed deficiency with Co(III) ions in the film structure. All films exhibited substantial electrical

F Švegl; B Orel; I Grabec-Švegl; V Kau?i?

2000-01-01

40

Structural, optical, and electrical properties of indium tin oxide films with corundum structure fabricated by a sol–gel route based on solvothermal reactions  

Microsoft Academic Search

This article reports on the fabrication of the Sn-doped In2O3 (ITO) films with corundum structure by a sol–gel route, using InCl3·4H2O, SnCl4 and de-ionized water as starting materials. Based on the hydrolysis of In3+ and Sn4+ in a solvothermal system using ethylenediamine as solvent, the aqueous sol was prepared, and acted as the precursor of the ITO films. The films

Dabin Yu; Weichao Yu; Debao Wang; Yitai Qian

2002-01-01

41

Effect of surface groups on the luminescence property of ZnO nanoparticles synthesized by sol-gel route  

NASA Astrophysics Data System (ADS)

Structural and optical properties of ZnO nanoparticles of diameter ~ 5 nm synthesized by a sol-gel route, have been studied using a variety of experimental techniques. The photoluminescence (PL) study carried out on these particles in the atmospheric and vacuum conditions shows a suppression of the defect related green luminescence (GL) band and a simultaneous enhancement of the near-band-edge ultra violet luminescence (UVL) when the surroundings of the nanoparticles are evacuated. This observation clearly suggests that GL is originating from certain groups that are physisorbed on the surface of the nanoparticles. Fourier transform infrared spectroscopy (FTIR) that has also been conducted at the vacuum and atmospheric conditions reveals the presence of the hydroxyl and the acetate groups in these nanoparticle samples. These groups are also found to be removed upon evacuation, suggesting that there is physical adsorption on the surface of the nanoparticles. When the PL spectrum is recorded again at the atmospheric condition, the GL intensity recovers almost up to its original value. Since there are substantial amount of water molecules present in air, which can source the hydroxyl groups, while the acetate groups are not expected to be abundant in air, this finding further suggests that the hydroxyl groups rather than the acetate groups are the likely cause for the GL emission observed in this system.

Sharma, A.; Singh, B. P.; Dhar, S.; Gondorf, A.; Spasova, M.

2012-02-01

42

Low-temperature synthesis of SrAl{sub 2}O{sub 4} by a modified sol-gel route: XRD and Raman characterization  

SciTech Connect

Among other alkaline-earth aluminates, the monoclinic (M) polymorph of SrAl{sub 2}O{sub 4} can be used as host material for Eu{sup 2+} luminescence based phosphors. With the aim of reducing the synthesis temperature of this polymorph, we have produced and characterized by XRD and Raman scattering solid solutions of the SrAl{sub 2-x}B{sub x}O{sub 4} system (x=<0.3) obtained by two different methods, a ceramic route and a modified sol-gel synthesis. Though the addition of boron lowers the temperature of obtention of the M polymorph in both type of samples, lower B contents are needed to stabilize the M form as single phase for samples prepared by the sol-gel method than through the ceramic route. In the sol-gel method, the M polymorph can be obtained at temperatures as low as 1200 deg. C, with a Boron content of just 1%. Rietveld profile analysis allows us to conclude that coexistence of the monoclinic and hexagonal polymorphs of SrAl{sub 2}O{sub 4} occurs for samples synthesized below an onset temperature of about 1000-1100 deg. C, that depends on the sample composition. Above those temperatures, only the monoclinic phase is formed.

Escribano, Purificacion [Departamento de Quimica Inorganica y Organica. Universitat Jaume I, 12071 Castellon (Spain); Marchal, Monica [Departamento de Quimica Inorganica y Organica. Universitat Jaume I, 12071 Castellon (Spain); Luisa Sanjuan, Maria [Instituto de Ciencia de Materiales de Aragon (Universidad de Zaragoza-CSIC), Facultad de Ciencias, 50009 Zaragoza (Spain); Alonso-Gutierrez, Pablo [Instituto de Ciencia de Materiales de Aragon (Universidad de Zaragoza-CSIC), Facultad de Ciencias, 50009 Zaragoza (Spain); Julian, Beatriz [Departamento de Quimica Inorganica y Organica. Universitat Jaume I, 12071 Castellon (Spain); Cordoncillo, Eloisa [Departamento de Quimica Inorganica y Organica. Universitat Jaume I, 12071 Castellon (Spain)]. E-mail: cordonci@qio.uji.es

2005-06-15

43

An improved sol-gel template synthetic route to large-scale CeO{sub 2} nanowires  

SciTech Connect

Large-scale CeO{sub 2} nanowires were prepared successfully by an improved sol-gel process within the nanochannels of porous anodic alumina templates. In this process, cerium nitrate and urea were used as precursors, cerium nitrate acted as cerium ions source, and urea offered a basic medium through its hydrolysis. The as-synthesized CeO{sub 2} nanowires can be indexed as a fluorite-structure and the size of nanowires is uniform, with diameters of about 70 nm. The formation mechanism of nanowires is also discussed here. This method is more efficient than a traditional sol-gel template process for small pore diameter templates.

Wu, G.S.; Xie, T.; Yuan, X.Y.; Cheng, B.C.; Zhang, L.D

2004-06-08

44

Microwave-assisted fluorolytic sol-gel route to iron fluoride nanoparticles for Li-ion batteries.  

PubMed

A simple microwave-assisted fluorolytic sol-gel synthesis of 30 nm sized FeF3 nanocrystals supported on partially reduced graphene oxide is reported. The as-fabricated nanostructures used as positive electrodes in Li-ion batteries show capacity retention as high as 150 mA h g(-1) even after having sustained repeated charge-discharge cycles. PMID:24257142

Di Carlo, Lidia; Conte, Donato E; Kemnitz, Erhard; Pinna, Nicola

2014-01-14

45

Solid-state NMR and XANES studies of lithium and silver silicate gels synthesized by the sol–gel route  

Microsoft Academic Search

The objective of this study is to understand the effect of low temperature sol–gel synthesis on the microstructural properties of lithium [xLi2O–(1?x)SiO2; x=0.1–0.8 in steps of 0.1] and silver [xAg2O–(1?x)SiO2; x=0.1–0.8 in steps of 0.1] silicate xerogels via solid state nuclear magnetic resonance (NMR) and X-ray absorption near edge structure (XANES) techniques. The Li silicate xerogels were analyzed with solid-state

A. A. Mrse; P. L. Bryant; F. J. Hormes; L. G. Butler; N. Satyanarayana; B. Rambabu

2003-01-01

46

Optical properties of undoped and Mg doped CuCrO2 powders synthesized by sol-gel route  

NASA Astrophysics Data System (ADS)

In this work, CuCrO2 was synthesized by sol-gel method using citric acid as a gelling agent. The different parameters like ratio of citric acid to metal ions, calcination temperature, and duration were studied. A green colored powder with particle size around 300 nm was formed at the calcination temperature of 800 °C for four hours duration. The increase in temperature has a profound impact on crystallite size and in turn effected the optical properties. Band gap of the obtained CuCrO2 has varied from 2.3 to 1.7 eV by increasing the temperature from 800 °C to 900 °C. Doping studies were performed by introducing Mg2+ ion to substitute Cr3+ in CuCrO2. X-ray powder diffraction and SEM studies on 2% Mg doped samples indicated a clear formation of side phases. According to the X-ray powder patterns, the reflections from side phases were increasing with the increase in doping concentrations of Mg from 2 to 5%. The side phases were found to be MgCr2O4 spinel and CuO. The band gap has decreased for doped samples in comparison to undoped one. In this paper, sol-gel synthesis and characterization by Xray powder diffraction, SEM studies and UV-Vis-Diffuse Reflectance spectra are presented.

Srinivasan, Radhakrishnan; Bolloju, Satish

2014-01-01

47

Fabrication and structural properties of LaFeO3 nanowires by an ethanol ammonia-based sol gel template route  

NASA Astrophysics Data System (ADS)

Highly ordered LaFeO3 nanowire arrays of composite oxides were synthesized within porous anodic aluminum oxide (AAO) templates by an ethanol ammonia-based sol gel route. The results of scanning electron microscopy and transmission electron microscopy revealed that the obtained LaFeO3 nanowires had a uniform length and diameter, which were determined by the thickness and the pore diameter of the applied AAO template. Energy-dispersive X-ray spectroscopy demonstrated that the stoichiometric LaFeO3 was formed. Furthermore, the results of X-ray diffraction and selected-area electron diffraction indicated that the LaFeO3 nanowires had a perovskite-type crystalline structure. It is expected that the novel and effective technique presented in this article would also be appropriate for the preparation of nanowires of other mono-component or multi-component oxides.

Yang, Z.; Huang, Y.; Dong, B.; Li, H.-L.

2005-08-01

48

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

49

Controlled synthesis of highly ordered LaFeO{sub 3} nanowires using a citrate-based sol-gel route  

SciTech Connect

Highly ordered LaFeO{sub 3} nanowires of complex oxide were controlled synthesized with a porous anodic aluminum oxide (AAO) template by a citrate-based sol-gel route. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the LaFeO{sub 3} nanowires formed a uniform length and diameter, which were determined by the thickness and the pore diameter of the AAO template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that the LaFeO{sub 3} nanowires had a perovskite-type crystal structure. Furthermore, X-ray photoelectron spectroscopy (XPS) demonstrated that stoichiometric LaFeO{sub 3} was formed.

Yang Zhi [College of Chemistry and Chemical Engineering, Lanzhou University, Gansu, Lanzhou 730000 (China); Huang Yi [College of Chemistry and Chemical Engineering, Lanzhou University, Gansu, Lanzhou 730000 (China); Dong Bin [College of Chemistry and Chemical Engineering, Lanzhou University, Gansu, Lanzhou 730000 (China); Li Hulin [College of Chemistry and Chemical Engineering, Lanzhou University, Gansu, Lanzhou 730000 (China)]. E-mail: lihl@lzu.edu.cn

2006-02-02

50

Homoleptic gallium(III) and indium(III) aminoalkoxides as precursors for sol-gel routes to metal oxide nanomaterials.  

PubMed

New homoleptic aminoalkoxides of gallium(III) and indium(III) of the types M4{(OC2H4)2NMe}6 [M = Ga (1), In (2)] and [Ga{(OC2H4)3N}]n (3), as well as a previously described Ga2(OC2H4NMe2)6 (A) have been prepared by isopropoxo(chloro)-aminoalkoxo exchange reactions and characterised by elemental analyses, FT-IR and 1H NMR spectroscopy. Formation of a star-shaped Ga[Ga{mu-eta3:eta1-(OC2H4)2NMe}2]3 (1.4CHCl3) and a zigzag linear In4{mu-eta3:eta1-(OC2H4)2NMe}6 (2.6CHCl3), as revealed by X-ray single crystal structures, reflects the structural diversity among N-methyldiethanolaminate derivatives. Their hydrolyses in boiling water, either in presence or absence of tetraalkylamonium bromide, have been studied and, for gallium derivatives, compared with similar hydrolytic reactions of Ga(OiPr)3. The hydrolysed products were studied by FT-IR, TG-DTA and XRD techniques. For gallium derivatives, transition from orthorhombic Ga(O)OH phase of as-prepared powder to phase pure rhombohedral- and monoclinic-Ga2O3 occurred at about 500 degrees C and 700 degrees C, respectively, whereas cubic In(OH)3 phase of as-prepared powder of 2 was converted to cubic In2O3 at 250 degrees C. Partial hydrolyses were also performed and evolution of the particle size in solution was recorded by light scattering measurements. Various sol-gel processing parameters such as concentration and hydrolysis ratio (h) were studied in order to stabilise nano-sized colloidal suspensions for access to thin films by spin coating. The N-methyldiethanolamine derivatives 1 and 2 were found to be the most suitable candidates for sol-gel processing. The transparent Ga2O3 and In2O3 films obtained on glass or Si wafers from spin-coating of 1 and 2, respectively, were characterised by SEM, EDX and XRD. PMID:19319402

Mishra, Shashank; Daniele, Stéphane; Petit, Sarah; Jeanneau, Erwann; Rolland, Marc

2009-04-14

51

Sol-gel synthesis and characterization of nanocrystalline (Bi0.5Na0.5)TiO3 powders from the poly vinyl alcohol evaporation route  

NASA Astrophysics Data System (ADS)

Nanocrystalline pure perovskite phase bismuth sodium titanate (Bi0.5Na0.5)TiO3(BNT) powders have been prepared by a sol-gel method from the poly vinyl alcohol evaporation route, bismuth nitrate [Bi(NO3)3], tetra-butyl titanate [Ti(OC4H9)4] and sodium acetate(CH3COONa) were used as raw materials and poly vinyl alcohol(PVA) as the sol-gel forming solvent. Stoichiometric amounts of the individual raw materials were thoroughly mixed in accordance with the BNT composition to form the stock solution. The pH of the stock was adjusted to 1-3 by adding acetate. Aqueous solution of PVA[10%(w/v)] was then added to the cationic mixture with thorough stirring. The weight ratio of the cationic mixture to the PVA aqueous solution was maintained at 2:1. The resulting viscous liquid was then heated over a hot crucible up to form a fluffy dry gel. The fluffy dry gels were calcined at different temperatures and times and then cooled to room temperature naturally. The X-ray powder diffraction(XRD) patterns of the heat-treated powders were obtained using a Bruker D8 Advance X-ray diffractometer with Cu K? radiation and nickel filter. Scanning electron microscope (SEM) studies of the NBT powders were performed using a JSM-6700F electron microscope. Phase-pure BNT powders were obtained at 550°C for 2-2.5h which is relatively lower calcination temperature than other reports. The BNT powders consists of phase-pure perovskite nanocrystals with an average size of 100-200nm.

Haitao, Liu; xiaohui, Wang; Longtu, Li

2009-09-01

52

Coupling sol-gel synthesis and microwave-assisted techniques: a new route from amorphous to crystalline high-surface-area aluminium fluoride.  

PubMed

A non-aqueous sol-gel Al-based fluoride has been subjected to the microwave solvothermal process. The final material depends on the temperature heat treatment used. Three types of material have been prepared: 1) for low temperature heat treatment (90 degrees C) X-ray amorphous alkoxy fluoride was obtained; 2) for the highest temperature used (200 degrees C) the metastable form beta-AlF3 was obtained with a very large surface area of 125 m2 g(-1). The mechanism of the amorphous=crystalline transformation has been rationalised by the occurrence of a decomposition reaction of the gel fluoride induced by the microwave irradiation. 3) Finally, at intermediate temperature (180 degrees C) a multi-component material mixture exhibiting a huge surface area of 525 m2 g(-1) has been obtained and further investigated after mild post-treatment fluorination using F2 gas. The resulting aluminium-based fluoride still possesses a high-surface-area of 330 m2 g(-1). HRTEM revealed that the solid is built from large particles (50 nm) identified as alpha-AlF3, and small ones (10 nm), relative to an unidentified phase. This new high-surface-area material exhibits strong Lewis acidity as revealed by pyridine adsorption and catalytic tests. By comparison with other materials, it has been shown that whatever the composition/structure of the Al-based fluoride materials, the number of strong Lewis acid sites is related to the surface area, highlighting the role of surface reconstruction occurring on a nanoscopic scale on the formation of the strongest Lewis acid sites. PMID:18491305

Dambournet, Damien; Eltanamy, Gehan; Vimont, Alexandre; Lavalley, Jean-Claude; Goupil, Jean-Michel; Demourgues, Alain; Durand, Etienne; Majimel, Jérôme; Rudiger, Stephan; Kemnitz, Erhard; Winfield, John M; Tressaud, Alain

2008-01-01

53

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

PubMed

Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxidic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size <30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures. PMID:16736767

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

2006-04-01

54

Crystallization behaviors and electric properties of (Pb0.8Ca0.2)TiO3 thin films prepared by a sol-gel route  

NASA Astrophysics Data System (ADS)

The pure tetragonal perovskite (Pb0.8Ca0.2)TiO3 (PCT) thin films deposited on (1 1 1)Pt/Ti/SiO2/Si substrate were successfully achieved by a sol-gel route, and the influence of pyrolysis temperature on crystallization behaviors and electric properties of the PCT films was investigated. It was found that the film pyrolyzed at 450 °C could be crystallized at temperature as low as 450 °C, while the film pyrolyzed at 350 °C is amorphous under the same crystallization temperature. It was also found that the PCT films pyrolyzed at different temperatures could be fully crystallized when the crystallization temperature was raised to 600 °C, and compared to the film pyrolyzed at 350 °C, the film pyrolyzed at 450 °C exhibited higher (1 0 0) orientation and possessed enhanced electric properties (remanent polarization ˜19.5 ?C/cm2, piezoelectric constant ˜125 pm/v, pyroelectric coefficient ˜310 ?C/m2K).

Chi, Q. G.; Zhu, H. F.; Lin, J. Q.; Chen, C. T.; Wang, X.; Chen, Y.; Lei, Q. Q.

2013-05-01

55

Dielectric Relaxation, Electrical Conductivity and Impedance Response of BaNb2O6 Synthesized by Sol-Gel and Solid State Reaction Route: A Comparative Study  

NASA Astrophysics Data System (ADS)

BaNb2O6 (BN)--an important precursor material for the synthesis of lead free relaxors, is synthesized in the nano phase using a modified Sol-Gel route in which the gel is formed by an aqueous solution of BaCl2, NbF5 and citric acid. The gel on decomposition at 700 °C yielded the nano phase of BaNb2O6 with particle size 48 nm. This is the lowest temperature for the formation of BaNb2O. Material is also prepared using the conventional solid state method in which the dominant columbite phase forms at 1100 °C after heating (6 h) with comparatively larger particle size of ~1 ?m. X-ray diffraction analysis confirms that the BaNb2O6 prepared by both the methods stabilize in orthorhombic crystal structure. Dielectric relaxation is observed and the mechanism of relaxation is elucidated. Conducting charges and free charges both contribute to the dielectric relaxation in the materials. Electrical properties of the materials are studied using impedance spectroscopic technique. Detailed analysis of impedance spectrum suggests that the electrical properties are strongly temperature dependent. AC conduction activation energies are estimated from Arrheneus plots and conduction mechanism is discussed.

Singh, K. N.; Chauhan, B. R.; Bajpai, P. K.

2011-11-01

56

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

PubMed

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 15.65nm 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. 5h with pseudo first order rate constants of 5.85×10(-3) and 8.38×10(-3)min(-1), respectively. PMID:24835935

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

2014-10-15

57

A simple route utilizing surfactant-assisted templating sol-gel process for synthesis of mesoporous Dy2O3 nanocrystal.  

PubMed

A simple route of combined sol-gel process with surfactant-assisted templating technique was successfully employed for the first time to synthesize nanocrystalline mesoporous Dy(2)O(3) with narrow monomodal pore size distribution under mild conditions. The nanocrystalline Dy(2)O(3) with monomodal mesoporous characteristic was ultimately achieved by controlling the hydrolysis and condensation steps of dysprosium n-butoxide modified with acetylacetone in the presence of laurylamine hydrochloride surfactant aqueous solution. The synthesized material was methodically characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), N(2) adsorption-desorption, Brunauer-Emmett-Teller (BET) surface area analysis, and Barrett-Joyner-Halenda (BJH) pore size distribution analysis. The particle size of the synthesized Dy(2)O(3) in nanosized range obtained from the SEM and HRTEM micrographs was in good accordance with the crystallite size estimated from the XRD result. The N(2) adsorption-desorption result exhibited hysteresis pattern with single loop, indicating the existence of monomodal mesopore. The extremely narrow pore size distribution with mean pore diameter in the mesopore region of the synthesized Dy(2)O(3) was also confirmed by the BJH result. PMID:16647076

Sreethawong, Thammanoon; Chavadej, Sumaeth; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

2006-08-01

58

Synthesis by sol-gel route and characterization of Yttria Stabilized Zirconia coatings for thermal barrier applications  

Microsoft Academic Search

This paper deals with the development of new synthesis techniques for functional materials such as Yttria Stabilized Zirconia (YSZ) used in the field of thermal barriers coatings. Currently, Thermal Barrier Coatings (TBCs) are manufactured by dry route technologies (EB-PVD or plasma spray) but such methods are directional and often require costly investments and complicated operations. We have carried out significant

C. Viazzi; J. P. Bonino; F. Ansart

2006-01-01

59

Synthesis of Nanostructured and Nanoporous TiO2-AgO Mixed Oxide Derived from a Particulate Sol-Gel Route: Physical and Sensing Characteristics  

NASA Astrophysics Data System (ADS)

Nanocrystalline TiO2-AgO thin films and powders were prepared by an aqueous particulate sol-gel route at the low temperature of 573 K (300 °C). Titanium tetraisopropoxide and silver nitrate were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the phase composition of the mixed oxide depends upon the annealing temperature, being a mixture of TiO2 and AgO in the range 573 K to 773 K (300 °C to 500 °C) and a mixture of TiO2, AgO, and Ag2O at 973 K (700 °C). Furthermore, one of the smallest crystallite sizes was obtained for TiO2-AgO mixed oxide, being 4 nm at 773 K (500 °C). Field emission-scanning electron microscopic (FE-SEM) and atomic force microscopic (AFM) images revealed that the deposited thin films had nanostructured and nanoporous morphology with columnar topography. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response toward low concentrations of CO gas ( i.e., 25 ppm) at low operating temperature of 473 K (200 °C), resulting in an increase of the thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, TiO2-AgO sensors follow the power law for the detection of CO gas.

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

2011-08-01

60

Low temperature nanocrystalline TiO2-Fe2O3 mixed oxide by a particulate sol-gel route: Physical and sensing characteristics  

NASA Astrophysics Data System (ADS)

Nanocrystalline TiO2-Fe2O3 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route at the low temperature of 300 °C. Titanium(IV) isopropoxide and iron(III) chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powder crystallised at the low temperature of 300 °C, containing anatase-TiO2 and hematite-Fe2O3 phases. Furthermore, it was found that Fe2O3 retarded the anatase-to-rutile transformation up to 500 °C. The activation energies for crystallite growth of TiO2 and Fe2O3 components in the binary system were calculated 10.62 and 0.67 kJ/mol, respectively. Moreover, one of the smallest crystallite sizes was obtained for TiO2-Fe2O3 binary mixed oxide, being 6 nm at 300 °C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanostructured morphology. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of CO gas (i.e., 25 ppm) at low operating temperature of 150 °C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, TiO2-Fe2O3 sensors follow the power law for the detection of CO gas.

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

2012-09-01

61

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

62

Effects of parameters of sol–gel process on the phase evolution of sol–gel-derived hydroxyapatite  

Microsoft Academic Search

It has been established that hydroxyapatite powders can be produced using an alkoxide-based sol–gel technique. Nanocrystalline powders of hydroxyapatite (HA) were prepared from Ca(NO3)2·4H2O and PO(OC2H5)3 as calcium and phosphorus precursors, respectively, using a sol–gel route. For a number of samples, sol of phosphorus was first hydrolyzed for 24h with distilled water. The sol temperature, aging time and heat treatment

Hossein Eshtiagh-Hosseini; Mohammad Reza Housaindokht; Mohammad Chahkandi

2007-01-01

63

The Microscopic Magnetic Properties of W-type Hexaferrite Powder Prepared by A Sol-Gel Route  

SciTech Connect

Magnetic particles of W-type barium-calcium hexaferrite (BaCa{sub 2}Fe{sub 16}O{sub 27}) have been synthesized using a Stearic acid gel route. The gel precursors were dried at 100 deg. C for 2 hrs and then calcinated at 650 deg. C, 750 deg. C, 850 deg. C and 950 deg. C for 4 hrs in a furnace and slowly cooled to room temperature in order to obtain barium-calcium hexaferrite particles. The microscopic magnetic properties of prepared samples studying using Moessbauer spectroscopy. Moessbauer spectra of all samples were recorded at room temperature. Mossbauer parameters like Isomer shift, Quadruple splitting etc. were calculated with respect to iron foil. Barium calcium hexaferrite samples heated at 650 deg. C, 750 deg. C, 850 deg. C show relaxation type Moessbauer spectra along with paramagnetic doublet. The intensity of paramagnetic doublet increases with temperature confirm the presence of ferrous ions in the samples, where as sample calcinated at 950 deg. C confirm the presence of ferrimagnetic phase with partial super paramagnetic nature of prepared hexaferrite sample.

Jotania, Rajshree; Chauhan, Chetna [Material Science Research Laboratory, Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380 009 (India); Sharma, Pooja [Department of Physics, Saurashtra University, Rajkot 360 005 (India)

2010-12-01

64

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

65

Dispersion and photoluminescence of free-metal phtalocyanine doped in sol–gel polyphenylsiloxane glass films  

Microsoft Academic Search

The optical absorption and photoluminescence of metal-free phtalocyanine (H2Pc) in a glassy matrix were discussed regarding the preparation method used. We show that fluorescent monodisperse free metal phtalocyanine can be doped in polyphenylsiloxane glass films using a non-aqueous sol–gel derived method. No fluorescence study of metal-free phtalocyanine doped in polysiloxane sol–gel materials has been reported so far due to the

Bouzid Menaa; Masahide Takahashi; Yomei Tokuda; Toshinobu Yoko

2008-01-01

66

Vegetal nanoclusters in hybrid silica films prepared by sol-gel spin coating technique  

Microsoft Academic Search

Hybrid sol-gel films containing Rosemary extract nanoclusters embedded into hybrid silica network have been successfully synthesized using the sol-gel procedure by exploiting the template route, in association with an adequate spin-coating method. Formation of film precursor sols and effect of selected amounts of octyl trimethoxysilane and ethyl oleate succinic anhydride into the starting acid sols on the sol-gel product size

I. Lacatusu; N. Badea; A. Murariu; C. Pirvu; A. Meghea

2011-01-01

67

SURFACE CHARGE OF SOL-GEL DERIVED ALUMINAS AS A FUNCTION OF CALCINATION TEMPERATURE  

Microsoft Academic Search

The sol-gel route for preparing alumina is thought to yield a unique molecular structure. Thus the powder characteristics of sol-gel derived aluminas are expected to be different from alumina powders derived by traditional processing methods. In this study wet alumina gels, after the sol-gel reaction was completed, were dried and calcined at 25C, 300C, 500C, 800C, 1100C, and 1400C following

BURTRAND I. LEE; LARRY L. HENCH

1986-01-01

68

Temperature dependence of the dielectric properties of mesoporous silica films prepared by a sol–gel route in the presence of polyether modified polydimethylsiloxane  

Microsoft Academic Search

Mesoporous silica films were prepared from tetraethylorthosilicate by an acid-catalyzed sol–gel process in the presence of\\u000a side-chain polyether modified polydimethylsiloxane. The samples were characterized using Fourier transform infrared spectroscopy,\\u000a differential thermal analysis and thermogravimetric analysis, field emission scanning electron microscopy, and atomic force\\u000a microscopy. Furthermore, the dielectric properties of the silica films annealed at different temperatures were investigated\\u000a at frequencies

Dong DongNi; Ni Wang; Xiaobo Liu; Weidong Xue; Wencheng Hu

69

Development of the FTIR properties of nano-structure silica gel doped with different rare earth elements, prepared by sol-gel route  

Microsoft Academic Search

Structural characteristics of pure silica gel (silica-xerogel, SiO2) and silica gel doped with some rare earth elements (REEs) such as, praseodymium Pr3+, and Europium Eu3+, Erbium Er3+ and Holmium Ho3+ ions, with different concentrations ranging from 1 up to 6%, in the form of monolith materials were prepared by sol-gel technique,\\u000a Using tetra-ethoxysilane as precursor materials, which are of particular

I. K. Battisha; A. El Beyally; S. Abd El Mongy; A. M. Nahrawi

2007-01-01

70

A novel route to control refractive index of sol-gel derived nano-porous silica films used as broadband antireflective coatings  

Microsoft Academic Search

A relatively new method to adjust refractive index of nano-porous silica films rapidly and continuously is reported. The thin films were prepared with the base\\/acid two-step catalytic sol-gel process and the dip-coating method. The structure, reflective spectra and refractive index of the films were analyzed with TEM, AFM, SEM, spectrophotometer, and ellipsometery, respectively. The experimental results have shown that the

Guangming Wu; Jue Wang; Jun Shen; Tianhe Yang; Qinyuan Zhang; Bin Zhou; Zhongsheng Deng; Bin Fan; Dongping Zhou; Fengshan Zhang

2000-01-01

71

Effect of Annealing Temperature on the Optical and Structural Properties of Dip-Coated Al2O3 Thin Films Prepared by Sol-Gel Route  

Microsoft Academic Search

Thin films of Al2O3 were prepared by the sol-gel process. Dip-coating technique was used for deposition of the Al2O3 thin films onto glass substrates. Optical and structural properties of the films were investigated with respect to the annealing temperature (100-500°C). The structure of these films was determined by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was performed for the analysis

F. E. Ghodsi; M. Mafakheri; A. Novinrooz

2005-01-01

72

A sol–gel route using propylene oxide as a gelation agent to synthesize spherical NiAl 2O 4 nanoparticles  

Microsoft Academic Search

Spherical NiAl2O4 nanoparticles with large surface area were successfully synthesized by a sol–gel method using propylene oxide as a gelation agent. The formation process of the resulting nanoparticles is described and characterized by TG-DTA, XRD, BET and TEM. A pseudo-spinel structure was formed at 700°C and a spinel NiAl2O4 structure was formed at 800°C by the reaction of NiO at

Hongtao Cui; Marcos Zayat; David Levy

2005-01-01

73

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

74

Acetone gas-sensing performance of Sr-doped nanostructured LaFeO 3 semiconductor prepared by citrate sol–gel route  

Microsoft Academic Search

Nanocrystalline La1?xSrxFeO3 (x = 0, 0.1, 0.2, 0.3 and 0.4) was prepared by sol–gel citrate method. The structural and microstructural characterization has been carried out with the help of X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. XRD studies confirm the formation of LaFeO3 with perovskite phase. Further studies by Fourier transform infrared spectroscopy were also conducted. DC electrical properties of

P. A. Murade; V. S. Sangawar; G. N. Chaudhari; V. D. Kapse; A. U. Bajpeyee

2011-01-01

75

Derivation of the optical constants of spin coated CeO 2–TiO 2–ZrO 2 thin films prepared by sol–gel route  

Microsoft Academic Search

Ternary thin films of cerium titanium zirconium mixed oxide were prepared by the sol–gel process and deposited by a spin coating technique at different spin speeds (1000–4000rpm). Ceric ammonium nitrate, Ce(NO3)6(NH4)2, titanium butoxide, Ti[O(CH2)3CH3]4, and zirconium propoxide, Zr(OCH2CH2CH3)4, were used as starting materials. Differential calorimetric analysis (DSC) and thermogravimetric analysis (TGA) were carried out on the CeO2–TiO2–ZrO2 gel to study

F. E. Ghodsi; F. Z. Tepehan; G. G. Tepehan

2011-01-01

76

Structural, magnetic and Mössbauer studies of (BiFeO3)0.7-(SrFe12O19)0.3 nanocomposite prepared by a sol-gel route  

NASA Astrophysics Data System (ADS)

The nanocomposite (BiFeO3)0.7-(SrFe12O19)0.3 has been prepared by a sol-gel route and characterized by XRD, TEM, TGA/DTA, dc magnetization and 57Fe Mössbauer spectroscopy. The hyperfine parameters obtained from Mössbauer spectroscopy indicate formation of pure hexaferrite phase of SrFe12O19 (SRF) in the nanocomposite (NC). The NC exhibits typical hysteresis loops with significantly altered magnetization parameters (saturation magnetization, coercivity and remnant magnetization) in comparison with that of the pristine SRF and BiFeO3 (BFO) nanoparticles (NPs). The ZFC-FC curves show a divergence in low temperature region which confirms the irreversible character of magnetization.

Das, A.; Roychowdhury, A.; Pati, S. P.; Bandyopadhyay, S.; Das, D.

2014-04-01

77

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

78

Sol–gel-fluorination synthesis of amorphous magnesium fluoride  

Microsoft Academic Search

The sol–gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150–350m2\\/g (HS-MgF2). The H2 type hysteresis of nitrogen adsorption–desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH3 temperature-programmed

J. Krishna Murthy; Udo Gross; Stephan Ruediger; Erhard. Kemnitz; John M. Winfield

2006-01-01

79

Effect of Annealing Temperature on the Optical and Structural Properties of Dip-Coated Al2O3 Thin Films Prepared by Sol-Gel Route  

NASA Astrophysics Data System (ADS)

Thin films of Al2O3 were prepared by the sol-gel process. Dip-coating technique was used for deposition of the Al2O3 thin films onto glass substrates. Optical and structural properties of the films were investigated with respect to the annealing temperature (100-500°C). The structure of these films was determined by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was performed for the analysis of surface morphology. For determination of the optical constants of Al2O3 thin films, UV-Visible spectrophotometry measurements were carried out. Annealing temperature affects the structural and optical properties of the Al2O3 thin films. The refractive index and extinction coefficient of the films at 550 nm wavelength increase from 1.56 to 1.66, and from 3.41 × 10-5 to 5.54 × 10-5, respectively while optical band gap and thickness of the films decrease from 4.15 eV to 4.11 eV, and 360 nm to 260 nm, respectively, by increasing annealing temperature from 100°C to 500°C.

Ghodsi, F. E.; Mafakheri, M.; Novinrooz, A.

80

Phase and electrical properties of PZT thin films embedded with CuO nano-particles by a hybrid sol-gel route  

NASA Astrophysics Data System (ADS)

Pb(Zr0.52Ti0.48)O3 or PZT thin films embedded with CuO nano-particles were successfully prepared by a hybrid sol-gel process. In this process, CuO (0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1 wt. %) nanopowder was suspended in an organometallic solution of PZT, and then coated on platinised silicon substrate using a spin-coating technique. The influence of CuO nano-particles' dispersion on the phase of PZT thin films was investigated. XRD results showed a perovskite phase in all films. At the CuO concentration of 0.4-1 wt. %, a second phase was observed. The addition of CuO nano-particles affected the orientation of PZT thin films. The addition was also found to reduce the ferroelectric properties of PZT thin films. However, at 0.2 wt. % CuO concentration, the film exhibited good ferroelectric properties similar to those of PZT films. In addition, the fatigue retention properties of the PZT/CuO system was observed, and it showed 14% fatigue at 108 switching bipolar pulse cycles while the fatigue in PZT thin films was found to be 17% at the same switching bipolar pulse cycles.

Sreesattabud, Tharathip; Gibbons, Brady J.; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda

2013-07-01

81

Densely packed single-crystal Bi{sub 2}Fe{sub 4}O{sub 9} nanowires fabricated from a template-induced sol-gel route  

SciTech Connect

Densely packed single-crystal Bi{sub 2}Fe{sub 4}O{sub 9} nanowires were successfully synthesized by a template-induced citrate-based sol-gel process. The structural properties of the nanowires were characterized using many techniques. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Bi{sub 2}Fe{sub 4}O{sub 9} nanowires possessed a uniform length and diameter, which were controlled by the thickness and the pore diameter of the applied porous anodic aluminum oxide (AAO) template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that Bi{sub 2}Fe{sub 4}O{sub 9} nanowires had an orthorhombic single-crystal structure. Furthermore, the energy-dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric Bi{sub 2}Fe{sub 4}O{sub 9} was formed. The possible formation mechanism of nanowires was also discussed. - Graphical abstract: The top view in low magnification of SEM images of Bi{sub 2}Fe{sub 4}O{sub 9} nanowires after AAO template is partly dissolved.

Yang Zhi [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Huang Yi [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Dong Bin [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Li Hulin [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Shi Sanqiang [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)]. E-mail: mmsqshi@polyu.edu.hk

2006-11-15

82

Synthesis of magnetic FexOy@silica-pillared clay (SPC) composites via a novel sol-gel route for controlled drug release and targeting.  

PubMed

Novel magnetic silica-pillared clay (SPC) materials with an ordered interlayered mesopore structure were synthesized via a two-step method including gallery molecular self-assembly and sol-gel magnetic functionalization, resulting in the formation of FexOy@SPC composites. Small-angle XRD, TEM and N2 adsorption-desorption isotherms results show that these composites conserved a regular layered and ordered mesoporous structure after the formation of FexOy nanoparticles. Wide-angle XRD and XPS analyses confirmed that the FexOy generated in these mesoporous silica-pillared clay hosts is mainly composed of ?-Fe2O3. Magnetic measurements reveal that these composites with different ?-Fe2O3 loading amounts possess super-paramagnetic properties at 300K, and the saturation magnetization increases with increasing Fe ratio loaded. Compared to the pure SPC, the in vitro drug release rate of the FexOy@SPC composites was enhanced due to the fact that the intensities of the SiOH bands on the pore surface of SPC decrease after the generation of FexOy. However, under an external magnetic field of 0.15T, the drug release rate of the FexOy@SPC composites decreases dramatically owing to the aggregation of the magnetic FexOy@SPC particles triggered by non-contact magnetic force. The obtained FexOy@SPC composites imply the possibility of application in magnetic drug targeting. PMID:24857471

Mao, Huihui; Liu, Xiaoting; Yang, Jihe; Li, Baoshan; Yao, Chao; Kong, Yong

2014-07-01

83

Absence of free carrier and paramagnetism in cobalt-doped ZnO nanoparticles synthesized at low temperature using citrate sol-gel route  

NASA Astrophysics Data System (ADS)

Cobalt-doped ZnO nanoparticles have been synthesized using a simple citrate sol-gel auto-combustion method. The XRD confirms nano-single phase and Wurtzite structure. Increased cobalt solubility from 15 to 20 % was observed in ZnO matrix due to low temperature synthesis. Room temperature paramagnetic contribution is observed for all the samples, since cobalt is a neutral dopant and no free carriers are produced. Normally, ferromagnetism is observed in ZnO due to carrier mediated interaction between transition metal ions and free carriers. Hence no ferromagnetism was observed and only paramagnetism was observed due to non-availability of free carriers for long range ferromagnetic interaction in our system. At higher doping, peak broadening of the highly intense XRD peak (101) was observed indicating formation of cobalt cluster (metal-metal) which reduces paramagnetism due to antiferromagnetic interaction and the magnetization value decreases to 0.00456 from 0.0076 emu/g. Absence of photoluminescence peak at 520 nm due to oxygen related defects also supports, the presence of paramagnetism in our samples, since oxygen defects are the another source of ferromagnetism in ZnO. Indirect evidence for the presence of cobalt clustering is also obtained from the photoluminescence studies which lead to concentration quenching of peaks. Photoluminescence studies exhibit NBE peak at 412 nm and defect peaks at 471 and 672 nm. The intensity of red emission peak at 672 nm remains constant whereas the intensity of the peaks at 412 and 471 nm increases and then decreases due to doping induced disorder leading to concentration quenching.

Sivagamasundari, A.; Pugaze, R.; Chandrasekar, S.; Rajagopan, S.; Kannan, R.

2013-10-01

84

New Developments in Sol-Gel Imaging.  

National Technical Information Service (NTIS)

This paper addresses the properties of sol-gel silica in relation to its potential to provide new devices for optical imaging. Although the sol-gel method opens the door to unprecedented levels of purity of silica materials, it is also beset with problems...

N. J. Phillips

1992-01-01

85

Electrochromism of Sol-gel Derived Niobium Oxide Films  

Microsoft Academic Search

Niobium oxide lms are promising cathodic electrochromics that in many aspects can compete with the more frequently studied WO 3 lms. The lms reported herein were prepared using the sol-gel route from a NbCl 5 precursor. The electrochromic properties were pronounced for crystalline lms that are heat-treated at 500 C and exhibited transmittance changes between coloured and bleached states of

M. MA CEK; B. OREL

86

Electrochromism of sol–gel derived niobium oxide films  

Microsoft Academic Search

Niobium oxide films are promising cathodic electrochromics that in many aspects can compete with the more frequently studied WO3 films. The films reported herein were prepared using the sol–gel route from a NbCl5 precursor. The electrochromic properties were pronounced for crystalline films heat-treated at 500°C and exhibited transmittance changes between coloured and bleached states of 60% in the ultraviolet (UV)

M Ma?ek; B Orel

1998-01-01

87

Structural characterization of sol-gel lanthanum cobaltite thin films  

Microsoft Academic Search

The present paper is focused on structural, microstructural and compositional studies on nanophasic LaCoO3 thin films obtained by the sol-gel route. The sample structure and microstructure were investigated by Glancing Incidence X-Ray Diffraction (GIXRD) and X-Ray microdiffraction (MicroXRD), whereas the surface and in-depth chemical composition was studied by X-Ray Photoelectron Spectroscopy (XPS). All the films are structurally homogeneous and not

E Bontempi; L Armelao; D Barreca; L Bertolo; G Bottaro; E Pierangelo; L. E Depero

2002-01-01

88

Thin hydroxyapatite coatings via sol–gel synthesis  

Microsoft Academic Search

Production of hydroxyapatite coatings using an alkoxide-based sol–gel route requires control of solution aging time and heating schedule. 31P nuclear magnetic resonance spectroscopy was used to investigate the changes during aging of the sol and thermal gravimetric analysis employed to study the behavior of the xerogels as a function of temperature, while final products were determined using X-ray diffraction. Results

K. A. Gross; C. S. Chai; G. S. K. Kannangara; B. Ben-Nissan; L. Hanley

1998-01-01

89

Solid-state tunable lasers based on dye-doped sol-gel materials  

SciTech Connect

The sol-gel process is a solution synthesis technique which provides a low temperature chemical route for the preparation of rigid transparent matrix materials. The luminescent organic dye molecules, rhodamine 6G and coumarin 540A have been incorporated, via the sol-gel method, into aluminosilicate and organically modified silicate host matrices. Synthesis, laser oscillation and photostability for these systems are reported. The improved photostability of these materials with respect to comparable polymeric host materials is discussed.

Dunn, B.; Mackenzie, J.D.; Zink, J.I.; Stafsudd, O.M.

1992-03-01

90

Improving CdS quantum-dot materials by the sol-gel method  

Microsoft Academic Search

In this paper we discuss our approaches and results for the preparation of improved semiconductor quantum dot materials by the sol-gel method. By taking advantage of the low- temperature sol-gel route, the nanostructure and optical properties of CdS quantum dots were greatly improved for device applications. Pore-free sodium borosilicate (NBS) glasses and organically modified silicates (ORMOSILs) were used as matrices

Chia-Yen Li; Yu-Hua Kao; Kazutaka Hayashi; Toshimi Takada; John D. MacKenzie; Koo I. Kang; San-Goo Lee; Nasser Peyghambarian; Masayuki Yamane; Guang-Wen Zhang; S. Iraj Najafi

1994-01-01

91

Laser-induced deposition of sol–gel alumina coating on stainless steel under wet condition  

Microsoft Academic Search

Excimer laser (KrF gas with wavelength 248nm) was used to deposit alumina coating onto stainless steel substrates through a sol–gel route. Sol–gel alumina coating was first applied on the substrate surface and then immediately irradiated with the excimer laser to initiate the deposition of alumina from the sol onto the substrate surface. The composition and microstructure of alumina coatings obtained

Y. Adraider; Y. X. Pang; F. Nabhani; S. N. Hodgson; Z. Y. Zhang

2011-01-01

92

Sol-gel deposited electrochromic coatings  

SciTech Connect

Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

Ozer, N.; Lampert, C.M.

1995-06-01

93

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

94

Process ceramic fibers by Sol-Gel  

Microsoft Academic Search

The Sol-Gel process may transform the materials of construction chemical engineers make and use--thin films, fibers, and powders. The advantage of the Sol-Gel technology is the ability to produce high purity products at low temperatures. For example, silica film is used to passivate integrated circuits. To achieve this, the native silicon substrate now is oxidized at about 1,000C for a

M. E. P. Fernandez de; Cheolho Kang; P. L. Mangonon

1993-01-01

95

Sol-gel technology for biomedical engineering  

Microsoft Academic Search

Sol-gel derived silica possess many promising features, including low-temperature preparation procedure, porosity, chemical and physical stability. Applications exploiting porous materials to encapsulate sensor molecules, enzymes and many other compounds, are devel- oping rapidly. In this paper some potential applications, with emphasis on biomedical and environmental ones, are reviewed. The material preparation procedure is described and practical remarks on silica-based sol-gels

H. PODBIELSKA; A. ULATOWSKA-JAR

96

Sol/gel transition of chitosan solutions.  

PubMed

This work studies the occurrence of sol/gel transition and the gel rheology for chitosan solution under various conditions. Experiments were conducted in an oscillatory shear apparatus with small amplitude, using a Rheometrics SR-5 rheometer, with Couette and parallel plate geometries. The experimental results demonstrate that the sol/gel transition concentration and the elastic modulus (G') for CS gel decrease as the pH value and the molecular weight (Mw) increase. However, the sol/gel transition concentration and G' became independent of Mw when Mw exceeded a threshold. The higher ionization constant, Kp, is responsible for the higher sol/gel transition concentration in a formic acid solution than in an acetic acid solution with equivalent molar concentration. The elastic modulus G' of a CS gel increases with temperature, which relationship differs from that for many polysaccharides, and can be understood through classical rubber elastic theory. Finally, a gel whose concentration was barely above the sol/gel point exhibited aging, and its G' and G" declined rather than increase with time, accompanied by a reversal from the sol/gel state back to the sol state. This is an uncommon aging behavior for a polysaccharide and a detailed explanation is provided. PMID:16370243

Rwei, S P; Chen, T Y; Cheng, Y Y

2005-01-01

97

Some studies on TiO2 films deposited by sol-gel technique  

Microsoft Academic Search

TiO2 films are extensively used in various applications including optical multi-layers, sensors, photo catalysis, environmental purification, and solar cells etc. These are prepared by both vacuum and non-vacuum methods. In this paper, we present the results on TiO2 thin films prepared by a sol-gel spin coating process in non-aqueous solvent. Titanium isopropoxide is used as TiO2 precursor. The films were

K. Narasimha Rao; M. Vishwas; Sudhir Kumar Sharma; K. V. Arjuna Gowda

2008-01-01

98

Sol-gel entrapped cobalt complex  

SciTech Connect

This work describes optimized conditions for preparation of a cobalt complex entrapped in alumina amorphous materials in the form of powder. The hybrid materials, CoNHG, were obtained by a nonhydrolytic sol-gel route through condensation of aluminum chloride with diisopropylether in the presence of cobalt chloride. The materials were calcined at various temperatures. The presence of cobalt entrapped in the alumina matrix is confirmed by ultraviolet visible spectroscopy. The materials have been characterized by X-ray diffraction (XRD), surface area analysis, thermogravimetric analysis (TGA), differential thermal analyses (DTA) and transmission electron microscopy (TEM). The prepared alumina matrix materials are amorphous, even after heat treatment up to 750 deg. C. The XRD, TGA/DTA and TEM data support the increase of sample crystallization with increasing temperature. The specific surface area, pore size and pore diameter changed as a function of the heat treatment temperature employed. Different heat treatment temperatures result in materials with different compositions and structures, and influence their catalytic activity. The entrapped cobalt materials calcined at 750 deg. C efficiently catalyzed the epoxidation of (Z)-cyclooctene using iodozylbenzene as the oxygen donor.

Lima, Omar J. de; Papacidero, Andrea T.; Rocha, Lucas A.; Sacco, Herica C.; Nassar, Eduardo J.; Ciuffi, Katia J.; Bueno, Luciano A.; Messaddeq, Younes; Ribeiro, Sidney J.L

2003-03-15

99

High surface area sol–gel alumina–titania nanocatalyst  

Microsoft Academic Search

Alumina–titania mixed oxide nanocatalysts with molar ratios = 1:0.5, 1:1, 1:2, 1:5 have been synthesized by adopting a hybrid\\u000a sol–gel route using boehmite sol as the precursor for alumina and titanium isopropoxide as the precursor for titania. The\\u000a thermal properties, XRD phase analysis, specific surface area, adsorption isotherms and pore size details along with temperature\\u000a programmed desorption of ammonia are presented. A

P. Padmaja; K. G. K. Warrier; M. Padmanabhan; W. Wunderlich

2009-01-01

100

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

101

Neutron detector using sol-gel absorber  

DOEpatents

An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

Hiller, John M. (Oak Ridge, TN); Wallace, Steven A. (Oak Ridge, TN); Dai, Sheng (Knoxville, TN)

1999-01-01

102

Hybrid sol-gel optical materials  

DOEpatents

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Zeigler, J.M.

1993-04-20

103

Hybrid sol-gel optical materials  

DOEpatents

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Zeigler, John M. (Albuquerque, NM)

1993-01-01

104

Hybrid sol-gel optical materials  

DOEpatents

Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

Zeigler, John M. (Albuquerque, NM)

1992-01-01

105

F-doped ZnO by sol-gel spin-coating as a transparent conducting thin film  

Microsoft Academic Search

This paper reports a simple non-alkoxide sol-gel route for depositing F-doped ZnO thin film on glass substrates. Ammonium\\u000a fluoride and zinc acetate were used as the dopant precursor and starting material for ZnO, respectively. After the first crystallization\\u000a at 550°C in air, the sol-gel spin coated ZnO:F thin films at a F concentration < 5 at. % showed a nanosized

Gil Mo Nam; Myoung Seok Kwon

2011-01-01

106

F-doped ZnO by sol-gel spin-coating as a transparent conducting thin film  

Microsoft Academic Search

This paper reports a simple non-alkoxide sol-gel route for depositing F-doped ZnO thin film on glass substrates. Ammonium fluoride and zinc acetate were used as the dopant precursor and starting material for ZnO, respectively. After the first crystallization at 550°C in air, the sol-gel spin coated ZnO:F thin films at a F concentration 5 at. % degraded the microstructures, electrical

Gil Mo Nam; Myoung Seok Kwon

2011-01-01

107

Nanocrystalline spin coated sol–gel hydroxyapatite thin films on Ti substrate: Towards potential applications for implants  

Microsoft Academic Search

Sol-gel spin coating is a promising process to obtain hydroxyapatite (HA) thin films. It is an alternative route to the hydroxyapatite deposition techniques usually employed to cover orthopaedic or dental titanium implant surfaces. The sol–gel (SG) parameters leading to a pure and crystalline HA coatings on Ti substrate were determined. They allow to reach a stoichiometric hydroxyapatite composition (ideal Ca\\/P

Adele Carradò; Nathalie Viart

2010-01-01

108

DTA and TGA characterization of sol-gel hydrotalcites  

Microsoft Academic Search

Double layered hydroxides with hydrotalcite structure were synthesized by the sol-gel precess using aluminum and magnesium alkoxides as precursors. The thermal decomposition of sol-gel hydrotalcites was studied by TGA and DTA methods. The sol-gel hydrotalcites show thermal stability up to 550 °C.

T. Lopez; E. Ramos; P. Bosch; M. Asomoza; R. Gomez

1997-01-01

109

Sol-Gel Derived Hafnia Coatings  

NASA Technical Reports Server (NTRS)

Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

2002-01-01

110

Viscoelasticity near the sol-gel transition  

Microsoft Academic Search

Measurements of viscoelastic properties near the sol-gel transition demonstrate that viscoelastic phenomena are described by power laws. To describe these phenomena, we derive the distribution of relaxation times for branched polymers, both in the reaction bath and in the dilute solution. From this spectrum we can compute viscoelastic properties such as the shear relaxation modulus G(t) and the complex shear

James E. Martin; Douglas Adolf; Jess P. Wilcoxon

1989-01-01

111

DEPOSITION OF PLCT THICK FILMS BY A MODIFIED SOL-GEL PROCESSING  

Microsoft Academic Search

The PLCT thick films were spin-deposited on various substrates by using a modified sol-gel process. The crystallization, surface morphology and the chemical state's properties of the PLCT thick films have been investigated. It is revealed that the success of this route is due to the elimination of the agglomeration among the nanometer particles. SEM observation shows that the PLCT thick

XIAOWU YUAN; DINGQUAN XIAO; ZHAOHUI PU; HONG LIU; JIAGANG WU; JIANGUO ZHU

2006-01-01

112

Innovative materials based on sol gel technology  

NASA Astrophysics Data System (ADS)

We review the sol-gel based new materials which were prepared in our laboratory including: tunable lasers, active waveguides, luminescent solar concentrators, electrochromic, photochromic and gasochromic plates for smart windows, chemical and biological sensors, semiconductor quantum dots and complexes of rare earth ions. In this paper we present the firstly obtained results of the Eu sulfide nanocrystalline (NCs) powder material and doped in the sol-gel based zirconia films. The powder and films were studied by high resolution transmittance electron microscopy (HRTEM), energy dispersive X-ray spectroscopy analysis (EDS) and luminescence spectroscopy. Eu sulfide nanocrystals (NCs) ranging between 8 and 10 nm were obtained as powder and 3-4 nm incorporated in zirconia film.

Reisfeld, Renata; Saraidarov, Tsiala

2006-01-01

113

Sol-gel preparation of nanostructured adsorbents  

Microsoft Academic Search

This paper reports sol-gel synthesis and properties of several major ceramic adsorbents. Nanostructured y-alumina, zirconia and titania adsorbents with uniform pore size distribution and an average pore diameter of about 3 nm are prepared by hydrolysis and condensation of corresponding metalorganic precursors. The as-synthesized adsorbents are in their meta-stable phases, and transform to their stable phases upon heat-treatment. The phase

Y. S. Lin; S. G. Deng

1999-01-01

114

Ring-Resonator/Sol-Gel Interferometric Immunosensor  

NASA Technical Reports Server (NTRS)

A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

Bearman, Gregory; Cohen, David

2007-01-01

115

Sol-gel coatings for optoelectronic devices  

Microsoft Academic Search

Nb2O5 prepared by a sol-gel process in form of coatings and aerogels are new materials which present interesting properties: (a) the coatings present electrochromic properties and exhibit a blue coloration under Li+ insertion with 100% reversible variation of the optical transmission in the visible and near infrared range between 80% and 20% and have a high chemical stability (tested up

C. O. Avellaneda; Marcelo A. Macedo; Aariovaldo O. Florentino; Michel A. Aegerter

1994-01-01

116

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

117

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

118

Er3+-activated photonic structures fabricated by sol-gel and rf-sputtering techniques  

NASA Astrophysics Data System (ADS)

The realization of photonic structures operating at visible and near infrared frequencies is a highly attractive scientific and technological challenge. Since optical fiber innovation, a huge of activity has been performed leading to interesting results, such as optical waveguides and planar lightwave circuits, microphotonic devices, optical microcavities, nanowires, plasmonic structures, and photonic crystals. These systems have opened new possibilities in the field of both basic and applied physics, in a large area covering Information Communication Technologies, Health and Biology, Structural Engineering, and Environment Monitoring Systems. Several materials and techniques are employed to successfully fabricate photonic structures. Concerning materials, Er3+-activated silica-based glasses still play an important role, although recently interesting results have been published about fluoride glass-ceramic waveguides. As far as regards the fabrication methods sol-gel route and rf sputtering have proved to be versatile and reliable techniques. In this article we will present a review of some Er3+-activated photonic structures fabricated by sol gel route and rf sputtering deposition. In the discussion on the sol-gel approach we focus our attention on the silica-hafnia binary system presenting an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO2-HfO2 waveguides activated by Er3+ ions. In order to put in evidence the reliability and versatility of the sol-gel route for photonics applications four different confined structures are briefly presented: amorphous waveguides, coated microspheres, monolithic waveguide laser, and core-shell nanospheres. As examples of rf sputtering technique, we will discuss Er3+-activated silica-hafnia and silica-germania waveguides, the latter system allowing fabrication of integrated optics structures by UV photo-imprinting. Finally, two examples of photonic crystal structures, one prepared by sol-gel process and the other one fabricated by rf sputtering deposition, will be illustrated.

Ferrari, M.; Alombert-Goget, G.; Armellini, C.; Berneschi, S.; Bhaktha, S. N. B.; Boulard, B.; Brenci, M.; Chiappini, A.; Chiasera, A.; Duverger-Arfuso, C.; Féron, P.; Gonçalves, R. R.; Jestin, Y.; Minati, L.; Moser, E.; Nunzi Conti, G.; Pelli, S.; Rao, D. N.; Retoux, R.; Righini, G. C.; Speranza, G.

2009-05-01

119

A Sol-Gel Precursor as a Powder Binder for PZT Ceramic Fabrication  

Microsoft Academic Search

A lead zirconate titanate (PZT) precursor sol was prepared by a diol sol-gel route and used as a binder for assisting the uniaxial die pressing of PZT powders. The powders, of composition Pb(Zr0.52Ti0.48) O3, were prepared by a two step mixed oxide route using lead carbonate, zirconia and titania starting powders. The densification characteristics of the powders, which were not

S. Tangwiwat; S. J. Milne

1999-01-01

120

Preparation and bioactivity of sol-gel macroporous bioactive glass  

Microsoft Academic Search

Bioactive glass is well known for its ability of bone regeneration, and sol-gel bioactive glass has many advantages compared with melt-derived bioactive glass. 3-D scaffold prepared by the sol-gel method is a promising substrate material for bone tissue engineering and large-scale bone repair. Porous sol-gel glass in the CaO-SiO2-P2O5 system with macropores larger than 100 ?m was prepared by the

Zhihua Zhou; Jianming Ruan; Jianpeng Zou; Zhongcheng Zhou

2008-01-01

121

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

Microsoft Academic Search

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

Matthew Hales; Wayde Martens; Theodore Steinberg

2010-01-01

122

Beta zeolite supported sol-gel TiO2 materials for gas phase photocatalytic applications.  

PubMed

Beta zeolite supported sol-gel TiO(2) photocatalytic materials were prepared according to a sol-gel route in which high specific surface area Beta zeolite powder was incorporated into the titanium isopropoxide sol during the course of the sol-gel process. This led to an intimate contact between the zeolite surface and the TiO(2) precursors, and resulted in the anchorage of large amounts of dispersed TiO(2) nanoparticles and in the stabilization of TiO(2) in its anatase form, even for high TiO(2) wt. contents and high calcination temperatures. Taking the UV-A photocatalytic oxidation of methanol as gas phase target reaction, high methanol conversions were obtained on the Beta zeolite supported TiO(2) photocatalysts when compared to bulk sol-gel TiO(2), despite lower amounts of TiO(2) within the photoactive materials. The methanol conversion was optimum for about 40 wt.% TiO(2) loading and calcination temperatures of 500-600°C. PMID:21177024

Lafjah, Mama; Djafri, Fatiha; Bengueddach, Abdelkader; Keller, Nicolas; Keller, Valérie

2011-02-28

123

Sol-Gel Derived Nanocrystalline Fluoridated Hydroxyapatite Powders and Nanostructured Coatings for Tissue Engineering Applications  

NASA Astrophysics Data System (ADS)

Nanocrystalline fluoridated hydroxyapatite (FHA) powders and coatings with a chemical composition of Ca10(PO4)6OH2- x F x (where x values were selected equal to 0.0 ,0.5, 1.0, 1.5, and 2.0) were prepared through a modified simple sol-gel technique in comparison with conventional alkoxide-based sol-gel route . X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, pF-meter with a fluorine-sensitive electrode, and inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis techniques were employed in order to evaluate phase composition, particle size distribution, morphology, functional groups, fluorine content, and purity of prepared FHA nanopowders, respectively. SEM analysis was used to study the surface morphology and cross section of the FHA coatings, deposited on 316L stainless steel substrate. Results indicated that single-phase and homogeneous FHA nanopowders with carbonate peaks in the FTIR spectrum were synthesized through the modified sol-gel technique. TEM analysis revealed that fluorapatite (FA) powder was composed of nanosized particles, ~25 nm in size, with polyhedron shape and straight corners. In the modified sol-gel technique, polymerization and gelation kinetic of the sol were significantly improved without any need to use additives or pH control. Uniform, dense, well-adhered, and compacted FHA coatings were formed on the 316L stainless steel substrate after 24 hours of aging.

Mohammadi Zahrani, E.; Fathi, M. H.; Alfantazi, A. M.

2011-11-01

124

Multiwalled carbon nanotubes embedded in sol–gel derived TiO 2 matrices and their use as room temperature gas sensors  

Microsoft Academic Search

Sol–gel TiO2\\/Multiwall Carbon Nanotubes composites obtained by the Ti-isopropoxide route are reported as room temperature sensitive coatings.\\u000a The effect of functionalizing the carbon nanotubes in strong oxidizing acids prior to the sol–gel synthesis is studied in\\u000a the detection of acetone (CH3COCH3) and ammonia (NH3). Although, mixed oxide phases were found in the sol–gel oxide and composites, sensing was highly reproducible

M. Sánchez; R. Guirado; M. E. Rincón

2007-01-01

125

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

126

Thermosensitive sol-gel reversible hydrogels.  

PubMed

Aqueous polymer solutions that are transformed into gels by changes in environmental conditions, such as temperature and pH, thus resulting in in situ hydrogel formation, have recently attracted the attention of many investigators for scientific interest and for practical biomedical or pharmaceutical applications. When the hydrogel is formed under physiological conditions and maintains its integrity for a desired period of time, the process may provide various advantages over conventional hydrogels. Because of the simplicity of pharmaceutical formulation by solution mixing, biocompatibility with biological systems, and convenient administration, the pharmaceutical and biomedical uses of the water-based sol-gel transition include solubilization of low-molecular-weight hydrophobic drugs, controlled release, labile biomacromolecule delivery, such as proteins and genes, cell immobilization, and tissue engineering. When the formed gel is proven to be biocompatible and biodegradable, producing non-toxic degradation products, it will provide further benefits for in vivo applications where degradation is desired. It is timely to summarize the polymeric systems that undergo sol-gel transitions, particularly due to temperature, with emphasis on the underlying transition mechanisms and potential delivery aspects. This review stresses the polymeric systems of natural or modified natural polymers, N-isopropylacrylamide copolymers, poly(ethylene oxide)/poly(propylene oxide) block copolymers, and poly(ethylene glycol)/poly(D,L-lactide-co-glycolide) block copolymers. PMID:11755705

Jeong, Byeongmoon; Kim, Sung Wan; Bae, You Han

2002-01-17

127

Sol-gel derived ?-BBO thin film  

NASA Astrophysics Data System (ADS)

(beta) -BaB2O4((beta) -BBO) is known as one of the best inorganic nonlinear crystals. It is now widely used for frequency doubling, frequency mixing in the UV range and optical parametric oscillation in the UV and near infrared regions. To put this material into thin film form would make it very attractive for integrated optical devices. Vacuum deposition techniques are not suitable for the fabrication of borates thin films due to the difficult evaporation or sputtering of oxides based on light elements. The low processing temperature of the sol-gel method allows the formation of stoichiometric and expected oxygen coordination of BaB2O4 in liquid phase. (beta) -BBO thin films has been successfully prepared by the sol-gel method through hydrolysis of barium and boron alkoxides. The accomplishment of hydrolysis is found to be essential for the removal of residual organic at high temperatures. The choice of precursors, hydrolysis ratio, and thermal treatments have critical influences on the formation, the morphology and the nucleation of (beta) -BBO phase of the film. The undesirable interaction between the film and the substrate limits the formation of (beta) -BBO polycrystalline film to only a few selected substrates.

Nie, Wenjiang; Lurin, Christian L.; Paz-Pujalt, Gustavo R.

1992-12-01

128

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

129

Nonlinear Optical Properties of Semiconductor-Doped Sol-Gel Waveguides  

Microsoft Academic Search

Thin silica-titania films doped with CdS and PbS nanocrystals have been prepared by the sol-gel route. Their nonlinear properties have been studied using the techniques of degenerated four-wave mixing and m-lines with picosecond (ps) and nanosecond laser pulses. Depending on wavelength, doping level, and laser pulse duration, high negative nonlinearity was found for CdS-doped (n2 = -2 x 10-8 cm2

J. Fick; A. Martucci; M. Guglielmi; J. Schell

2000-01-01

130

Silica-based sol-gel films doped with active elements  

Microsoft Academic Search

The preparation of glassy films doped with rare earth ions is important for planar waveguide fabrication in active integrated optic devices. The sol-gel process is a promising route for the preparation of such films and the eventual overcoming of the problem of rare earth clustering. In the present work, both SiO2 and 90SiO2-10TiO2 films were prepared by spin coating on

R. M. Almeida; X. Orignac; D. Barbier

1994-01-01

131

Crystallisation Kinetics of ? Spodumene in Lithium Aluminosilicate Sol–Gel Glasses  

Microsoft Academic Search

ß-spodumene (LiAlSi2O6) is one of the crystalline phase of the lithium aluminosilicate (LAS) glass-ceramics, having a low thermal expansion coefficient. The sol–gel process is an advantageous processing route for LAS materials, compared to melting, as it avoids lithium oxide losses and formation of undesired crystalline phases. It is very important to understand the crystallisation kinetics in order to assess the

M. D. D. R. F. Moreira; I. M. Miranda Salvado; R. F. Silva

2004-01-01

132

The effect of lithiation on the electrochromism of sol-gel derived niobium oxide films  

Microsoft Academic Search

Niobium oxide films are promising cathodic electrochromic materials that in certain aspects can compete with the more frequently studied WOâ films. The films reported here were prepared using the sol-gel route from a NbClâ precursor. The electrochromic properties were pronounced for crystalline films heat-treated at 500 C exhibiting transmittance changes between the colored and bleached states of 60% in the

M. Macek; B. Orel; U. O. Krasovec

1997-01-01

133

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

134

Preparation and characterization of PZT solid solutions via sol–gel process  

Microsoft Academic Search

The present research describes a modified sol–gel process that has been developed for the preparation of lead zirconate titanate (PZT) (0.52\\/0.48) powders. In this route, diethanolamine (DEA) was used as a complexing agent to keep the metal ions in homogeneous solutions without undergoing precipitation. Drying treatment led to development of transparent gel network. Phase-pure perovskite structure was formed at 500°C.

Radhouane Bel Hadj Tahar; Noureddine Bel Hadj Tahar; Abdelhamid Ben Salah

2007-01-01

135

Preparation and characterization of PZT solid solutions via sol gel process  

Microsoft Academic Search

The present research describes a modified sol gel process that has been developed for the preparation of lead zirconate titanate (PZT) (0.52\\/0.48) powders. In this route, diethanolamine (DEA) was used as a complexing agent to keep the metal ions in homogeneous solutions without undergoing precipitation. Drying treatment led to development of transparent gel network. Phase-pure perovskite structure was formed at

Radhouane Bel Hadj Tahar; Noureddine Bel Hadj Tahar; Abdelhamid Ben Salah

2007-01-01

136

New Sol-Gel Synthesis of Ordered Nanostructured Doped ZnO Films  

Microsoft Academic Search

A novel sol-gel route to c-axis orientated undoped and Co, Fe, Mn and V doped ZnO films is reported. Sols were prepared from a hydrated zinc acetate precursor and dimethyl formamide (DMF) solvent. Films were spin-coated on to hydrophilic sapphire substrates then dried, annealed and post-annealed, producing almost purely uniaxial ZnO crystallites and a high degree of long-range structural order.

N. R. S. Farley; C. R. Staddon; L. X. Zhao; K. W. Edmonds; B. L. Gallagher; D. H. Gregory

2003-01-01

137

Sol–gel preparation of thick titania coatings aided by organic binder materials  

Microsoft Academic Search

Nanostructured titania has been reported to be used in many applications in areas ranging from optics via solar energy to gas sensors. We report in this paper a low-cost method of producing nanostructured titania coatings. TiO2 films were spin-coated on silicon substrates via methylcellulose (MC) aided aqueous sol–gel route using Ti(Obut)4–HAC–EtOH as starting materials. SEM, TGA, FTIR and XRD techniques

Wei Chen; Junying Zhang; Qi Fang; Shu Li; Jianxin Wu; Fanqing Li; Ke Jiang

2004-01-01

138

Two methods of obtaining sol–gel Nb2O5 thin films for electrochromic devices  

Microsoft Academic Search

Nb2O5 coatings prepared by the sol–gel route using the dip coating technique with sols prepared from alkoxide or chloroalkoxide (two different methods: sonocatalytic and conventional) precursors are a promising alternative for WO3 electrochromic coatings. The crystalline films (TT phase) sintered at 560 and 600°C are transparent and present a deep blue colour under Li+ ion insertion. Electrochemical stability is excellent

C. O. AVELLANEDA; A. PAWLICKA; M. A Aegerter

1998-01-01

139

Sol-gel derived bioactive hydroxyapatite\\/titania composite films on Ti6Al4V  

Microsoft Academic Search

The composite films consisting of the titania gel impregnated with hydroxyapatite (HAP) submicron particles were prepared on commercial Ti6Al4V plates processed by a sol-gel route. HAP powders were synthesized based on wet chemical precipitation method with Ca(NO3)24H2O and (NH4)2HPO4 as starting reagents. After being calcined at 900°C, HAP powders were ultrasonically scattered in ethanol to produce HAP sol. The titania

Bing Su; Guoqing Zhang; Xudong Yu; Chengtao Wang

2006-01-01

140

Sol–gel silica coatings on ZE41 magnesium alloy for corrosion protection  

Microsoft Academic Search

Silica coatings have been applied on the surface of ZE41 magnesium alloy following the organic sol–gel route and the dip-coating technique. Three different concentrations of sol solution and two densification temperatures of the coating (400°C and 500°C) were used to optimize the compaction of the coatings and as a result reach the corrosion protection of the metallic substrate tests in

A. J. López; E. Otero; J. Rams

2010-01-01

141

Preparation, characterization and photocatalytic activity of a novel nanostructure ZnO composite film derived sol-gel process using organic binder materials  

Microsoft Academic Search

A novel sol-gel-derived zinc oxide nanostructure has been prepared by spin-coating and investigated for the purpose of producing films. ZnO films were spin-coated on microscope glass slides via methylcellulose (MC) aided sol-gel route using zinc acetate-acetic acid-EtOH as starting materials and heat treatment. Scanning electron microscopy (SEM) investigations showed that relatively dense, crack-free and transparent ZnO composite films, as well

Mojtaba Nasr-Esfahani; Ali Khakifiroz; Nahid Tavakoli; Mohammad Hassan Soleimani

2010-01-01

142

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

143

Sol-gel processing of energetic materials  

SciTech Connect

As part of a new materials effort, we are exploring the use of sol- gel chemistry to manufacture energetic materials. Traditional manufacturing of energetic materials involves processing of granular solids. One application is the production of detonators where powders of energetic material and a binder are typically mixed and compacted at high pressure to make pellets. Performance properties are strongly dependent on particle size distribution, surface area of its constituents, homogeneity of the mix, and void volume. The goal is to produce detonators with fast energy release rate the are insensitive to unintended initiation. In this paper, we report results of our early work in this field of research, including the preparation of detonators from xerogel molding powders and aerogels, comparing the material properties with present state-of-the-art technology.

Tillotson, T.M.; Hrubesh, L.H.; Fox, G.L.; Simpson, R.L.; Lee, R.W.; Swansiger, R.W.; Simpson, L.R.

1997-08-18

144

One step antiglare sol—gel coating for screens by sol—gel techniques  

Microsoft Academic Search

Anti-reflection coatings on glass substrates were prepared by the application of sol—gel coatings of silica containing crystalline tin oxide particles. The sol was coated on commercially available float glass by dip-coating and spin-coating techniques. Increasing the surface roughness of the float glass (factor of 50) by a particulate coating material resulted in anti-reflection effects comparable to frosted glass. Haze and

C. Schelle; M. Mennig; H. Krug; G. Jonschker; H. Schmidt

1997-01-01

145

Ceramiques tritigenes a base d'orthosilicate de lithium: preparation sol-gel, mobilite du lithium et relachement du tritium. (Lithium orthosilicate ceramics: sol-gel preparation, lithium dynamics and tritium release).  

National Technical Information Service (NTIS)

Ceramics based on the lithium orthosilicate (Li(sub 4)SiO(sub 4)) are candidates as blanket materials for forthcoming fusion reactors. Lithium orthosilicate powders, with controlled stoichiometry, were prepared from sol-gel route. This method of processin...

M. Smaihi

1990-01-01

146

Sol-gel coating on acoustic wave devices: Thin film characterization and chemical sensor development  

SciTech Connect

We have investigated the use of porous oxide coatings, formed using sol-gel chemistry routes, as the discriminating elements of acoustic wave (AW) chemical sensors. These coatings provide several unique advantages: durability, high adsorption capacity based on large surface areas, and chemical selectivity based on both molecular size and chemical interactions. The porosity of these coatings is determined by performing nitrogen adsorption isotherms using the AW device response to mass changes to monitor the uptake of nitrogen at 77 K. These studies demonstrate how sol-gel chemistry and film-forming technique can be used to tailor the microstructure of thin coatings. The chemical sensitivity and selectivity obtained with this class of coatings will be demonstrated using several examples: hydrous titanate ion exchange coatings, zeolite/silicate microcomposite coatings, and surface-modified silicate films. 18 refs., 4 figs., 2 tabs.

Frye, G.G.; Brinker, C.J.; Ricco, A.J.; martin, S.J.; Hilliard, J.; Doughty, D.H.

1990-01-01

147

Preparation and characterization of PZT solid solutions via sol gel process  

NASA Astrophysics Data System (ADS)

The present research describes a modified sol-gel process that has been developed for the preparation of lead zirconate titanate (PZT) (0.52/0.48) powders. In this route, diethanolamine (DEA) was used as a complexing agent to keep the metal ions in homogeneous solutions without undergoing precipitation. Drying treatment led to development of transparent gel network. Phase-pure perovskite structure was formed at 500 °C. The crystallization behavior of the sol-gel-derived powders was studied by X-ray diffraction (XRD) and simultaneous thermal analysis. Differences between the sequence of phase formation encountered in the traditional (oxide-mix) synthesis and that in chemically derived lead zirconate titanate ceramics are discussed.

Bel Hadj Tahar, Radhouane; Bel Hadj Tahar, Noureddine; Ben Salah, Abdelhamid

2007-09-01

148

Structural and optical characterizations of YAG:Eu 3+ elaborated by the sol-gel process  

NASA Astrophysics Data System (ADS)

Sol-gel route has been successfully used to obtain pure Y 3Al 5O 12 and Y 3Al 5O 12:Eu 3+ powders. The formation process, the structure as well as the microstructure of the materials were analyzed by means of X-ray diffraction (XRD), thermal analysis (TG-TDA), infrared spectroscopy (IR) and scanning electron microscopy (SEM). It has been shown that sol-gel derived YAG powders crystallize around 900 °C whereas a temperature much higher is necessary to obtain this compound by solid state synthesis (?1500 °C). Laser induced luminescence spectra, as well as luminescence decays of Eu 3+ ions show undoubtedly the spectral features of a Eu 3+ emitting center embedded in a unique site of D 2 symmetry.

Boyer, Damien; Bertrand-Chadeyron, Geneviève; Mahiou, Rachid

2004-07-01

149

Potentiodynamic evaluation of sol–gel coatings with inorganic inhibitors  

Microsoft Academic Search

Sol–gel coatings were investigated as potential replacements for chromate-based surface treatments on aircraft aluminum alloys. Unlike chromate based treatments current sol–gel coatings do not have the ability to leach corrosion inhibitors upon coating damage and minimize corrosion of the unprotected area. As an alternative, environmentally compliant non-chromate inhibitors of Ce(NO3)3, NaVO3 and Na2MoO4 were incorporated into a Zr-epoxy sol–gel. Results

N. N. Voevodin; N. T. Grebasch; W. S. Soto; F. E. Arnold; M. S. Donley

2001-01-01

150

Silica scintillating materials prepared by sol-gel methods.  

National Technical Information Service (NTIS)

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 met...

D. W. Werst M. C. Sauer K. R. Cromack Y. Lin E. A. Tartakovsky

1993-01-01

151

Organofunctional Sol-Gel Materials for Toxic Metal Separation  

SciTech Connect

Inorganic-organic silica sol-gels grafted or encapsulated with organic ligands were prepared and found to selectively and reversibly remove target metal ions such as Cu2+, Cd2+, and Sr2+. These organofunctional sol-gel materials, which were easily prepared from off-the-shelf chemicals, were hydrophilic and showed fast kinetics of metal uptake. The sol-gels were easily regenerated and used in multi-cycle metal removal. In our search for new ligands for metal removal, we found that the reactions of thioacetal ligands with Hg2+ gave Hg(SCH2COOH)2. Our studies of organofunctional sol-gel materials for metal separation will be discussed.

Im, Hee-Jung; Yost, Terry L.; Yang, Yihui; Bramlett, J. Morris; Yu, Xiang-Hua; Fagan, Bryan C.; Allain, Leonardo R.; Chen, Tianniu; Xue, Ziling; Barnes, Craig E.; Dai, Sheng; Rocker, Lee E.; Sepaniak, Michael J.

2003-09-10

152

Molecular Growth Pathways in Silica Sol-Gel Polymerization.  

National Technical Information Service (NTIS)

An analytical protocol involving gas chromatography (GC), gas chromatography-mass spectrometry (GCMS), and sup 29 Si//sup 1/H/ NMR spectroscopy, was developed to determine the structures of the polysilicate intermediates formed during silica sol-gel polym...

S. D. Ramamurthi

1989-01-01

153

Production of continuous mullite fiber via sol-gel processing  

NASA Technical Reports Server (NTRS)

The development of a continuous ceramic fiber which could be used in rocket engine and rocket boosters applications was investigated at the Marshall Space Flight Center. Methods of ceramic fiber production such as melt spinning, chemical vapor deposition, and precursor polymeric fiber decomposition are discussed and compared with sol-gel processing. The production of ceramics via the sol-gel method consists of two steps, hydrolysis and polycondensation, to form the preceramic, followed by consolidation into the glass or ceramic structure. The advantages of the sol-gel method include better homogeneity and purity, lower preparation temperature, and the ability to form unique compositions. The disadvantages are the high cost of raw materials, large shrinkage during drying and firing which can lead to cracks, and long processing times. Preparation procedures for aluminosilicate sol-gel and for continuous mullite fibers are described.

Tucker, Dennis S.; Sparks, J. Scott; Esker, David C.

1990-01-01

154

Silica sol-gel immobilized amperometric biosensor for hydrogen peroxide  

Microsoft Academic Search

An amperometric enzyme electrode for hydrogen peroxide was developed via easy and effective enzyme immobilization using the sol-gel technique. The enzyme electrode comprises horseradish peroxidase (HRP) immobilized in the silica sol-gel matrix on a carbon paste electrode (CPE). Hydrogen peroxide was detected in the presence of hexacyanoferrate(II) as a mediator to transfer electrons between the electrode surface and hydrogen peroxide.

Juan Li; Swee Ngin Tan; Hailin Ge

1996-01-01

155

Sol-gel deposition of electrochromic copper oxide films  

Microsoft Academic Search

This paper discusses the optical and electrochromic properties of CuxO films deposited by sol-gel process. UV-VIS-NIR spectroscopy, SEM, X-ray Diffraction and X-ray Photoelectron spectroscopy have been employed in a study of structure and optical properties of coatings. The sol-gel process offers new approaches to optical properties of coatings prepared by the acid catalyzed reactions of alkoxides. CuxO polymeric solutions are

Nilgun Ozer; Fatma Tepehan

1993-01-01

156

Luminescence decay analysis of doped sol-gel films  

Microsoft Academic Search

Fluorescence decay of the well-known fluorophore, ruthenium (II) 4,7-diphenyl-1,10-phenanthroline perchlorate, has been studied in a series of sol-gel matrices, including non-polar methyltrimethoxysilane (MTMS) and highly polar tetraethylorthosilicate (TEOS)-based gels. Systematic changes in composition and processing techniques have been fabricated to examine the structural properties of sol-gel silicates for possible oxygen sensor supports. Measurements were performed using both brush-coated and spin-coated

Michael T. Murtagh; Michael Krihak; Hyeog-Chan Kwon; Mahmoud R. Shahriari

1996-01-01

157

Ceramic sol–gel composite coatings for electrical insulation  

Microsoft Academic Search

Electrically insulative alumina and silica-based coatings up to 500 ?m in thickness have been deposited on steel substrates using a sol–gel composite technology. Coatings are produced by spray depositing a ceramic paint consisting of fine ceramic powders dispersed in a sol–gel solution to form a coating. Coatings are then dried at 343 K and fired at 723 K to pyrolyze

Tim Olding; Michael Sayer; David Barrow

2001-01-01

158

New nonlinear Sol-Gel films exhibiting photorefractivity  

Microsoft Academic Search

The first photorefractive sol-gel film has been prepared by copolymerization of tetraethoxysilane and modified silane monomers having push-pull azobenzene and carbazole moieties. Thin films poled by corona discharge exhibited large quadratic nonlinearities (electrooptic coefficient râââ 17 pm\\/V, at 633 nm). Preliminary two-beam coupling measurements, without applying external electric field, showed photorefractivity of this new sol-gel material. 21 refs., 3 figs.

F. Chaput; J. P. Boilot; K. Cargnelli; M. Canva; Y. Lévy; A. Brun

1996-01-01

159

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

160

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

161

Conducting antimony-doped tin oxide films derived from stannous oxalate by aqueous sol gel method  

NASA Astrophysics Data System (ADS)

Nanocrystalline SnO 2:Sb films were prepared by a sol-gel route using C 6H 8O 7-triethanolamine (TEA) mixing aqueous solution with pH 6.5-7.0. Stannous oxalate and antimony trichloride were used as tin and antimony sources. IR, XRD FESEM, FETEM, UV-vis and four-point probe measurement were used to characterize sol-gel chemistry, structure, morphologies, optical and electrical properties. Mechanism of sol-gel reaction illuminated that existence of TEA supplied large numbers of active tin hydrate and ionized state carboxyl groups for tin and antimony chelation through the amido association with the ionized H + on -COOH of H 3L and H 2C 2O 4. The 6 at.% Sb-doped films with film thickness of 600 nm had sheet resistance as low as 42.85 ?/ when annealed at 450 °C for 10 min. Annealing temperature intensively altered sheet resistance and optimum was in the range of 450-500 °C. The longer annealing time caused Sb volatilization which led to the optimum doping level shifted from 6 to 12 at.%.

Liu, Tong Jun; Jin, Zheng Guo; Feng, Li Rui; Wang, Tao

2008-08-01

162

Bi-Sr-Co-O thermoelectrics prepared by sol-gel methods with modified gel decomposition  

NASA Astrophysics Data System (ADS)

We prepared misfit Bi2Sr2Co1.8Ox (Bi-222) phase as a member of a Bi-Sr-Co-O family. Two water based sol-gel methods were chosen with regard to the presence of a strongly hydrolysing Bi3+ ion - chelating route combining EDTA (ethylenediaminetetraacetic acid) and TEA (triethanolamine) and, secondly, water soluble polymer method using PEI (polyethylenimine). We focused on the influence of gel decomposition process on the grain size of precursor and, consequently, on the bulk density of the final samples. We tested decomposition in N2 atmosphere followed by a treatment in pure oxygen. The precursors decomposed in "N2/O2" regime were mainly composed of Bi2O3, SrCO3 and cobalt oxides with the grain size of approximately 50-100 nm. The powders arising from gel decomposition in air contained the desired Bi-Sr-Co-O oxide as the major phase independently of the chosen sol-gel method. The final sintered samples were almost single-phase with traces of the other pseudoternary phase Bi2Sr2CoOx independently of the decomposition atmosphere. For comparison, samples were also prepared by solid state reaction. The sol-gel prepared samples were always of higher bulk density with larger grains, moreover partly microstructurally ordered. These facts were also reflected in transport thermoelectric measurements.

Rubešová, K.; Hlásek, T.; Jakeš, V.; Sedmidubský, D.; Hejtmánek, J.

2012-02-01

163

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

164

Nanocrystalline spin coated sol-gel hydroxyapatite thin films on Ti substrate: Towards potential applications for implants  

NASA Astrophysics Data System (ADS)

Sol-gel spin coating is a promising process to obtain hydroxyapatite (HA) thin films. It is an alternative route to the hydroxyapatite deposition techniques usually employed to cover orthopaedic or dental titanium implant surfaces. The sol-gel (SG) parameters leading to a pure and crystalline HA coatings on Ti substrate were determined. They allow to reach a stoichiometric hydroxyapatite composition (ideal Ca/P atomic ratio 1.67) and a control of the growth of the crystalline phases. The samples, when observed by Scanning Electron Microscopy (SEM), exhibit grains of ca. 200 nm, well adapted for cell proliferation. The crystallisation of the HA films was thoroughly studied by X-Ray diffraction (XRD). The aim of this paper is to validate the sol-gel method as a processing method allowing the control of the mechanical state of the films and, in particular, of the residual stresses (RS) at metal-ceramic interfaces. These stresses were determined on titanium substrates. While the uncoated Ti substrates were in a compressive residual state, the coated ones were in a low tensile state. These results suggest that the sol-gel process is indeed a processing route to obtain HA coated Ti implants.

Carradò, Adele; Viart, Nathalie

2010-07-01

165

Synthesis of highly textured superconducting NdBa2Cu3O7-y thin films using an aqueous inorganic sol-gel dip coating technique  

NASA Astrophysics Data System (ADS)

In general, the sol-gel method is a very attractive route for ceramic synthesis because it permits direct fabrication of multi-component ceramics in different configurations without powder intermediates. This diversity, in which materials can be formed, has made the sol-gel method an important synthesis route in several domains of research. For (RE)Ba2Cu3O7-y superconducting thin film development, chemical solution deposition (CSD) techniques starting from sol-gel precursors can offer a cost-effective and more flexible large-scale alternative synthesis route in comparison to the common used vacuum techniques. This work describes the deposition of thin NdBa2Cu3O7-y layers on SrTiO3 single crystals based on a new sol-gel dip coating process using aqueous precursor solutions. Two inorganic aqueous sol-gel routes were investigated, a metal nitrate - citric acid based and a metal acetate - triethanol amine based solution.

Schoofs, B.; Mouganie, T.; Glowacki, B. A.; Cloet, V.; Hoste, S.; van Driessche, I.

2006-06-01

166

Sol-gel encapsulation for controlled drug release and biosensing  

NASA Astrophysics Data System (ADS)

The main focus of this dissertation is to investigate the use of sol-gel encapsulation of biomolecules for controlled drug release and biosensing. Controlled drug release has advantages over conventional therapies in that it maintains a constant, therapeutic drug level in the body for prolonged periods of time. The anti-hypertensive drug Captopril was encapsulated in sol-gel materials of various forms, such as silica xerogels and nanoparticles. The primary objective was to show that sol-gel silica materials are promising drug carriers for controlled release by releasing Captopril at a release rate that is within a therapeutic range. We were able to demonstrate desired release for over a week from Captopril-doped silica xerogels and overall release from Captopril-doped silica nanoparticles. As an aside, the antibiotic Vancomycin was also encapsulated in these porous silica nanoparticles and desired release was obtained for several days in-vitro. The second part of the dissertation focuses on immobilizing antibodies and proteins in sol-gel to detect various analytes, such as hormones and amino acids. Sol-gel competitive immunoassays on antibody-doped silica xerogels were used for hormone detection. Calibration for insulin and C-peptide in standard solutions was obtained in the nM range. In addition, NASA-Ames is also interested in developing a reagentless biosensor using bacterial periplasmic binding proteins (bPBPs) to detect specific biomarkers, such as amino acids and phosphate. These bPBPs were doubly labeled with two different fluorophores and encapsulated in silica xerogels. Ligand-binding experiments were performed on the bPBPs in solution and in sol-gel. Ligand-binding was monitored by fluorescence resonance energy transfer (FRET) between the two fluorophores on the bPBP. Titration data show that one bPBP has retained its ligand-binding properties in sol-gel.

Fang, Jonathan

167

Passive and active sol-gel materials and devices  

NASA Astrophysics Data System (ADS)

This paper examines sol-gel materials for photonics in terms of partnerships with other material contenders for processing optical devices. The discussion in four sections identifies semiconductors, amorphous and crystalline inorganic dielectrics, and amorphous and crystalline organic dielectrics as strategic agents in the rapidly evolving area of materials and devices for data communications and telecommunications. With Zyss, we trace the hierarchical lineage that connects molecular hybridization (chemical functionality), through supramolecular hybridization (collective properties and responses), to functional hybridization (device and system level constructs). These three concepts thread their way through discussions of the roles sol-gel glasses might be anticipated to assume in a photonics marketplace. We assign a special place to glass integrated optics and show how high temperature consolidated sol-gel derived glasses fit into competitive glass fabrication technologies. Low temperature hybrid sol-gel glasses that combine attractive features of organic polymers and inorganic glasses are considered by drawing on examples of our own new processes for fabricating couplers, power splitters, waveguides and gratings by combining chemical synthesis and sol-gel processing with simple photomask techniques.

Andrews, Mark P.; Najafi, S. Iraj

1997-07-01

168

Sol-gel derived contamination resistant antireflective coatings  

NASA Astrophysics Data System (ADS)

Silica-based sol-gel antireflective (AR) optical coatings are critical components for high peak power laser systems. It is well known that water vapor and volatile organic compounds in both the laser bay and target bay environments will reduce the antireflective efficiency and laser-damage resistance of the sol-gel AR coating. In this study, alkylation with organosilanes in the vapor state was investigated. Sol-gel AR coatings were vapor-phase treated with hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS) at room temperature, and the resulting post-treated sol-gel AR coatings were tested for their resistance to contamination by a series of volatile organic compounds. Contact angle measurements were taken to discern the degree of silanization. After the vapor treatment of sol-gel AR coatings with organosilanes, the spectral performance of the coatings were analyzed by spectrophotometer, both before and after the exposure to volatile organic compounds. It is found that the coatings treated with ammonia and HMDS show a better contamination resistant capability. After being contaminated 70 hours with hexane, the transmittance of the coatings presents no obvious decrease. And the vapor treatment produces an increase in their damage threshold at 1064 nm (10ns pulse width) as compared to untreated control samples.

Shen, Jun; Liu, Yuan; Wu, Guangming; Zhou, Bin; Zhang, Zhihua; Zhu, Yumei

2010-10-01

169

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

170

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

171

New Sol-Gel Synthesis of Ordered Nanostructured Doped ZnO Films  

Microsoft Academic Search

A novel sol-gel route to c-axis orientated undoped and Co, Fe, Mn and V doped\\u000aZnO films is reported. Sols were prepared from a hydrated zinc acetate\\u000aprecursor and dimethyl formamide (DMF) solvent. Films were spin-coated on to\\u000ahydrophilic sapphire substrates then dried, annealed and post-annealed,\\u000aproducing almost purely uniaxial ZnO crystallites and a high degree of\\u000along-range structural order.

N. R. S. Farley; C. R. Staddon; L. X. Zhao; K. W. Edmonds; B. L. Gallagher; D. H. Gregory

2003-01-01

172

The effect of lithiation on the electrochromism of sol-gel derived niobium oxide films  

SciTech Connect

Niobium oxide films are promising cathodic electrochromic materials that in certain aspects can compete with the more frequently studied WO{sub 3} films. The films reported here were prepared using the sol-gel route from a NbCl{sub 5} precursor. The electrochromic properties were pronounced for crystalline films heat-treated at 500 C exhibiting transmittance changes between the colored and bleached states of 60% in the ultraviolet (UV) and 80% in the visible and near-infrared spectral regions. The reversibility of electrochromic changes of thick niobium oxide films (d > 250 nm) was enhanced by lithiation.

Macek, M.; Orel, B.; Krasovec, U.O. [National Inst. of Chemistry, Ljubljana (Slovenia)

1997-09-01

173

Entrapment of enzymes in nanoporous sol-gels.  

PubMed

The prerequisite for many successful enzyme-based biotechnologies is the preparation of highly stable and active biocatalysts, which can be achieved effectively by immobilization. This chapter introduces the immobilization of enzymes by entrapment in nanoporous silica particles made in a sol-gel process. These easily tailorable materials have been proven very beneficial for a broad variety of applications of biocatalysts. Besides the spatial confinement in silica sol-gels, another advantage is given by the easy possibility of fine-tuning the physicochemical properties of the matrix itself to provide the ideal environment for the reaction and the biocatalyst. Preparation details are demonstrated using the process of immobilizing a lipase in a sol-gel matrix, which is chemically modified by using methyl-, ethyl-, propyl-, and i-butyltrimethoxysilane. The transesterification of canola oil with methanol is used as a model reaction. PMID:21553195

Buthe, Andreas

2011-01-01

174

Modification of sol-gel coatings by ion implantation  

NASA Astrophysics Data System (ADS)

In order to densify and to improve the physical properties, TiO2 sol-gel films, about 100 nm in thickness, on silica glass or silicon wafer were implanted with Ar+ or B+ ions. The refractive index of the as-dried films increased and the IR absorption band of OH disappeared after Ar+ implantation. Dehydration and densification of sol-gel films were enhanced by Ar+ implantation. On the other hand, the refractive index and the thickness of the films hardly changed by B+ implantation. However, IR absorption bands attributed to B-O bond were observed after B+ implantation. This suggests that sol-gel films could be chemically modified by ion implantation with reactive ion species.

Hirashima, Hiroshi; Adachi, Kenji; Imai, Hiroaki

1994-10-01

175

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

176

Sol-gel laser coatings at CEA Limeil-Valenton  

NASA Astrophysics Data System (ADS)

CEA Limeil-Valenton has embarked in a project called 'laser megajoule' (LMJ) consisting of the construction of a 2-MJ/500- TW (351-nm) pulsed Nd:glass laser and devoted to inertial confinement fusion research in France. Room temperature and atmospheric pressure deposited sol-gel coatings for antireflective (AR), highly reflective (HR) and polarizer uses, and silicone films for environmental protection have displayed remarkable optical and laser strength performance. Such coatings can be applied onto large area and at a low cost compared to conventional vacuum deposition techniques. CEA Limeil-Valenton is also maintaining sustained efforts to promote the sol-gel technology in other areas.

Floch, Herve G.; Belleville, Philippe F.

1997-10-01

177

Thin pyroelectric PLZT film obtained with sol-gel technology  

Microsoft Academic Search

The sol-gel technology (J. Zarzycki in J.Sol-Gel Sci. Technol. 8:17–22, 1997) and the spin coating were employed for the production\\u000a of PLZT 12\\/40\\/60 pyroelectric film. The starting materials were: lead acetate, lanthanum nitrate, metallo-organic compounds\\u000a of zirconium and titanium and acetic acid. An alumina substrate with pre-deposited lanthanum-strontium cobalt oxide (LSCO)\\u000a (H. Takahashi, et al in Phys. Rev. B. 57:15211–15218,

Andrzej ?ozi?ski

2007-01-01

178

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

179

Electrochromic properties of lithiated Co-oxide (Li x CoO 2) and Ni-oxide (Li x NiO 2) thin films prepared by the sol–gel route  

Microsoft Academic Search

Layered LixCoO2 and LixNiO2 thin films (x?1) were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H2O2. Structural changes during the processing of xerogel to final oxide were followed by X-ray diffraction and infrared spectroscopy. Electrochromic properties were determined with in-situ potentiodynamic, potentiostatic and galvanostatic spectroelectrochemical measurements. Single dipped films

Franc Švegl; Boris Orel; Ven?eslav Kau?i?

2000-01-01

180

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

181

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

182

Fabrication and characterization of evanescent wave coupled PbS quantum dots fiber amplifier based on sol-gel method  

Microsoft Academic Search

In this paper, size-tunable PbS semiconductor quantum dots were synthesized by sol-gel route and a novel optical fiber amplifier was proposed. Based on fused tapered fiber coupler, the PbS quantum dots film was deposited in the couple region and evanescent wave coupled semiconductor quantum dots fiber amplifier was fabricated. Due to the thinned fiber shape, evanescent wave penetrates into outer

Jiwen Yan; Fufei Pang; Zhenyi Chen; Tingyun Wang

2008-01-01

183

Effect of solute concentration on the structural and morphological properties of sol-gel derived CdO films  

NASA Astrophysics Data System (ADS)

The present work deals with the preparation of cadmium oxide (CdO) thin films through the sol-gel spin coating route on to glass substrates. The structural and surface morphological properties of the deposited films have been investigated and the influence of precursor solute concentration on these properties studied. Smooth, uniform CdO films with good crystalline quality have been obtained by controlling the precursor solute concentration and the results have been presented.

Rajammal, R.; Savarimuthu, E.; Arumugam, S.

2013-06-01

184

Sol–gel derived Pb(Zr,Ti)O 3 thin films: Residual stress and electrical properties  

Microsoft Academic Search

Pb(Zr,Ti)O3 compositions are under investigation for applications that include integrated capacitors, piezoelectric sensors, and actuators. Sol–gel synthesis and spin coating are popular routes to the formation of high quality, dense, crack free, insulating films. However, the electrical properties of the films are often different than those measured for bulk specimens of the same composition. Pb(Zr0.53Ti0.47)O3 films were deposited from a

R. J. Ong; T. A. Berfield; N. R. Sottos; D. A. Payne

2005-01-01

185

Synthesis of lanthanum oxide doped photocatalytic nano titanium oxide through aqueous sol–gel method for titania multifunctional ultrafiltration membrane  

Microsoft Academic Search

An all aqueous sol gel route has been demonstrated for the synthesis of titania multifunctional ultrafiltration membrane on\\u000a porous alumina substrate. Doping with lanthana was used to increase the thermal stability of anatase phase. This resulted\\u000a in a nanoporous membrane with considerable percentage of anatase phase even after consolidation at 800°C. The highly homogeneous\\u000a membranes with a thickness of ~4–5 ?m

K. A. Manjumol; V. S. Smitha; P. Shajesh; K. V. Baiju; K. G. K. Warrier

2010-01-01

186

Influence of PEG additive and annealing temperature on structural and electrochromic properties of sol–gel derived WO 3 films  

Microsoft Academic Search

Sol–gel derived tungsten oxide (WO3) films have been deposited by spin coating route using acetylated peroxotungstic acid (APTA) or a mixture of APTA and polyethylene\\u000a glycol (PEG) dissolved in ethanol as the precursor solution, followed by thermal treatment in air. The influence of PEG additive\\u000a and annealing temperature on the structural and electrochromic (EC) behavior of the films have been

Yanqun Fang; Xilian Sun; Hongtao Cao

187

Sol–gel nonhydrolytic synthesis of a hybrid organic–inorganic electrolyte for application in lithium-ion devices  

Microsoft Academic Search

A new inorganic–organic hybrid electrolyte was synthesized by a nonhydrolytic sol–gel simple route without specific treatment of the reagents. The hybrid ion conductor is prepared with citric acid (CA), tetraethyl-orthosilicate (TEOS) and ethylene glycol (EG), forming polyester chains. The time-consuming drying step, required in most of the chemical syntheses, is not necessary for the preparation of the present hybrid electrolyte,

F. L. Souza; P. R Bueno; E. R. Leite

2004-01-01

188

Sol–gel chemistry: evidence of redistributionat silicon atom induced by NaOH as catalystduring ageing  

Microsoft Academic Search

The influence of the ageing conditions on the properties of organic-inorganic hybrid solids obtained by sol–gel route using NaOH catalysis has been studied. The cases of 1,4-bis(trimethoxysilyl)benzene 1 (‘rigid’ precursor) and 1,4-bis(trimethoxysilylethyl)benzene 2 (‘more flexible’ one) have been investigated. The 29Si CP MAS NMR spectra of the silsesquioxanes clearly reveal that Si–O–Si bond cleavage and redistribution reactions occur when the

Geneviève Cerveau; Robert J. P Corriu; Éric Framery

2001-01-01

189

Template?Free Sol?Gel Synthesis of Hierarchically Macro? and Mesoporous Monolithic TiO2  

Microsoft Academic Search

Monolithic titania exhibiting a hierarchical, bimodal meso?macroporosity has been prepared through a template free sol?gel synthesis route. The macropore diameter can be controllably varied in the range 0.4–4 µm still maintaining a narrow pore size distribution. The macropores form as a consequence of parallel gelation and microscopic phase separation, where their relative kinetics determine the macropore diameter. We utilize the chelating

Stefan Backlund; Jarl B. Rosenholm; Mika Lindén

2007-01-01

190

Nitric oxide-releasing sol–gels as antibacterial coatings for orthopedic implants  

Microsoft Academic Search

To assess the benefits of nitric oxide (NO)-releasing sol–gels as potential antibacterial coatings for orthopedic devices, medical-grade stainless steel is coated with a sol–gel film of 40% N-aminohexyl-N-aminopropyltrimethoxysilane and 60% isobutyltrimethoxysilane. Upon converting the diamine groups in these films to diazeniumdiolate NO donors, the NO release from the sol–gel-coated stainless steel is evaluated at both ambient and physiological temperature. Sol–gel

Brian J. Nablo; Aaron R. Rothrock; Mark H. Schoenfisch

2005-01-01

191

Properties of nanostructured magnesium metatitanate prepared by the sol-gel technique  

Microsoft Academic Search

Nanometric powders of high purity were produced using alkoxides of magnesium and titanium as precursors for the sol-gel method. Formation of geikielite from the sol-gel powders was carried out by stepwise heating of the sol-gel precipitate, and the progress of the process was followed by XRPD, TGA and DTA. Low temperature treatment of the sol-gel products removed the solvent and

J. Zabicky; D. Zingerman; R. Shneck; E. Manor

1996-01-01

192

Comparative studies of “all sol–gel” electrochromic devices with optically passive counter-electrode films, ormolyte Li + ion-conductor and WO 3 or Nb 2O 5 electrochromic films  

Microsoft Academic Search

Laminated electrochromic (EC) devices are becoming increasingly important for making “smart” windows and switchable displays. Mostly, polymeric Li+ ionic conductors in combination with vacuum deposited active electrochromic and counter-electrode films are used. In this paper we report on the development of all sol–gel EC devices, that is, those where all three internal layers are prepared via the sol–gel route, including

B. Orel; U. Opara Krašovec; M. Ma?ek; F. Švegl; U. Lavren?i? Štangar

1999-01-01

193

Silica Sol Gel Micro-Laser on a Substrate and Method of Fabrication.  

National Technical Information Service (NTIS)

Silica sol gel micro-lasers and methods of fabricating micro-lasers on a chip or a wafer. A silica sol gel micro-laser includes a silica sol gel optical micro-cavity, a substrate, and a support member or pillar that extends between the micro-cavity and th...

K. J. Vahala L. Yang

2004-01-01

194

Wrinkling of a sol-gel-derived thin film  

Microsoft Academic Search

We report on the wrinkle formation in a thin film produced by the sol-gel method. Through the relaxation of stress, which results from the removal of the solvent during the drying process, an isotropic wavy pattern is generated in the form of skeletal branches. The patterns have a dominant wavelength satisfying a relationship of three-fourths order of thickness. Densification of

S. Joon Kwon; Jae-Hwan Park; Jae-Gwan Park

2005-01-01

195

Sol–gel transition and gelatinization kinetics of wheat starch  

Microsoft Academic Search

Rheological and optical microscopy experiments were conducted to monitor the sol–gel transition during gelatinization process of starch granules. During the gelatinization phenomenon, the grains grow and dissolve into the plasticizer leading to a drastic increase of the elastic modulus (G?) and the loss modulus (G?), and to their crossover as a consequence of the formation of a physical gel. The

F. Teyssandier; P. Cassagnau; J. F. Gérard; N. Mignard

2011-01-01

196

Bioactive glass nanoparticles obtained through sol-gel chemistry.  

PubMed

Different sol-gel strategies based on the Stöber method are proposed enabling preparation of nanoparticles of SiO2-CaO bioactive glass with different size, narrow size distribution and good dispersion capability. Eu(3+)-doped glass nanoparticles with luminescent properties can also be obtained. PMID:23772442

Lukowiak, Anna; Lao, Jonathan; Lacroix, Josephine; Nedelec, Jean-Marie

2013-07-28

197

Sol-gel synthesis and NMR characterization of ceramics  

Microsoft Academic Search

Sol-gel chemistry allows the low temperature synthesis of ceramic powders. The molecular engineering of alkoxide precursors leads to the crystallization of ceramic powders of controlled morphology and structure. Stable sols of tetragonal zirconia have been synthesized via the hydrolysis of chemically modified zirconium alkoxides. Complexing acetylacetone ligands slow down condensation processes and prevent the aggregation of nanosized zirconia particles. The

Jacques Livage; Florence Babonneau; Murielle Chatry; Laure Coury

1997-01-01

198

Sol-gel processing and automation of tunable ceramic materials  

NASA Astrophysics Data System (ADS)

Sol gel processing of ceramic materials has attracted much interest in the past decade because of its inherent advantages in homogeneity of the resulting powder, fine grain size, high purity, and ability to mix disparate materials well. Sol gel processing is particularly apt to tunable electroceramics such as barium strontium titanate (BST) because of the fine grain size and purity desirable in such materials. It may be desirable to develop a semiautomatic system to produce the tunable ceramic powder, thin film and ceramic devices. Thin film tunable ceramics can be deposited on to a substrate with or without conductive traces by using a microwave plasma deposition system. In this paper, we have shown such a system incorporating microwave power for calcination, binder burn out and final sintering to a near net shape manufacturing of ceramic devices. This paper also describes the sol gel processing method for BST and compares properties of materials prepared by the sol gel method and the more conventional carbonate and oxide powder method.

Selmi, Fathi; Varadan, Vasundara V.; Herner, B.; Varadan, Vijay K.

1993-07-01

199

Safe and Environmentally Acceptable Sol-gel Derived Pyrophoric Pyrotechnics  

SciTech Connect

It was demonstrated that highly porous sol-gel derived iron (III) oxide materials could be reduced to sub-micron-sized metallic iron by heating the materials to intermediate temperatures in a hydrogen atmosphere. Through a large number of experiments complete reduction of the sol-gel based materials was realized with a variety of hydrogen-based atmospheres (25-100% H{sub 2} in Ar, N{sub 2}, CO{sub 2}, or CO) at intermediate temperatures (350 C to 700 C). All of the resulting sol-gel-derived metallic iron powders were ignitable by thermal methods, however none were pyrophoric. For comparison several types of commercial micron sized iron oxides Fe2O3, and NANOCAT were also reduced under identical conditions. All resulting materials were characterized by thermal gravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (PXRD), as well as scanning and transmission electron microscopies (SEM and TEM). In addition, the reduction of the iron oxide materials was monitored by TGA. In general the sol-gel materials were more rapidly reduced to metallic iron and the resulting iron powders had smaller particle sizes and were more easily oxidized than the metallic powders derived from the micron sized materials. The lack of pyrophoricity of the smaller fine metallic powders was unexpected and may in part be due to impurities in the materials that create a passivation layer on the iron. Several recommendations for future study directions on this project are detailed.

Simspon, R L; Satcher, J H; Gash, A

2004-06-10

200

Stoichiometric hydroxyapatite obtained by precipitation and sol gel processes  

NASA Astrophysics Data System (ADS)

Three methods for obtaining hydroxiapatite (HA) are described. HA is a very interesting ceramic because of its many medical applications. The first two precipitation methods start from calcium and phosphorous compounds, whereas the third method is a sol-gel process that uses alcoxides. The products were characterized and compared. The observed differences are important for practical applications.

Vazquez, C. G.; Barba, C. P.; Munguia, N.

2005-06-01

201

Sol-gel multilayers applied by a meniscus coating process.  

National Technical Information Service (NTIS)

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 app...

J. A. Britten I. M. Thomas

1992-01-01

202

Sol–gel based alumina powders with catalytic applications  

Microsoft Academic Search

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

Maria Crisan; Maria Zaharescu; Valluri Durga Kumari; Machiraju Subrahmanyam; Dorel Crisan; Nicolae Dragan; M?lina R?ileanu; Mihaela Jitianu; Adriana Rusu; Gullapelli Sadanandam; Jakkidi Krishna Reddy

2011-01-01

203

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

204

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

205

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

206

All Sol-Gel Electrochromic Devices with Li + Ionic Conductor, WO 3 Electrochromic Films and SnO 2 Counter-Electrode Films  

Microsoft Academic Search

This paper reports on the development of all sol-gel EC devices, having the configuration WO3\\/ormolyte\\/SnO2:Mo, WO3\\/ormolyte\\/SnO2:Sb and WO3\\/ormolyte\\/SnO2:Sb:Mo, where all three internal layers, including the ionically conductive inorganic-organic hybrid (ormolyte), are prepared via the sol-gel route. The electrochemical and optical properties of EC devices are presented and their cycling stability and reversibility of their optical modulation assessed. The transmission modulation

B. Orel; U. Opara Krašovec; U. Lavren?i? Štangar; P. Judeinstein

1998-01-01

207

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

208

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 SiO2, 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 simular 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. The elemental composition and structure of the precursor molecules were characterized. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors.

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

2003-01-01

209

Calcium hydroxyapatite, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} ceramics prepared by aqueous sol-gel processing  

SciTech Connect

Aqueous sol-gel chemistry routes based on ammonium-hydrogen phosphate as the phosphorus precursor and calcium acetate monohydrate as source of calcium ions have been developed to prepare calcium hydroxyapatite samples with different morphological properties. In the sol-gel processes, an aqueous solutions of ethylene diamine tetra-acetic acid (EDTA) or tartaric acid (TA) as complexing agents were added to the reaction mixture. The monophasic Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} samples were obtained by calcination of precursor gels for 5 h at 1000 deg. C. The phase transformations, composition and micro-structural features in the polycrystalline samples were studied by thermoanalytical methods (TGA/DTA), infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD) and scanning electron microscopy (SEM). It was shown that adjusting the nature of complexing agent in the aqueous sol-gel processing can be used to control the morphology of the ceramic samples.

Bogdanoviciene, Irma [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania); Beganskiene, Aldona [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania); Tonsuaadu, Kaia [Laboratory of Inorganic Materials, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Glaser, Jochen [Institut fuer Anorganische Chemie, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen (Germany); Meyer, H.-Juergen [Institut fuer Anorganische Chemie, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen (Germany)]. E-mail: juergen.meyer@uni-tuebingen.de; Kareiva, Aivaras [Department of General and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania)]. E-mail: aivaras.kareiva@chf.vu.lt

2006-09-14

210

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

211

Synthesis of 45S5 Bioglass® via a straightforward organic, nitrate-free sol-gel process.  

PubMed

More than four decades after the discovery of 45S5 Bioglass® as the first bioactive material, this composition is still one of the most promising materials in the tissue engineering field. Sol-gel-derived bioactive glasses generally possess improved properties over other bioactive glasses, because of their highly porous microstructure and unique surface chemistry which accelerate hydroxyapatite formation. In the current study, a new combination of precursors with lactic acid as the hydrolysis catalyst have been employed to design an organic, nitrate-free sol-gel procedure for synthesizing of 45S5 Bioglass®. This straightforward route is able to produce fully amorphous submicron particles of this glass with an appropriately high specific surface area on the order of ten times higher than that of the melt-derived glasses. These characteristics are expected to lead to rapid hydroxyapatite formation and consequently more efficient bone bonding. PMID:24857490

Rezabeigi, Ehsan; Wood-Adams, Paula M; Drew, Robin A L

2014-07-01

212

Improving CdS quantum-dot materials by the sol-gel method  

NASA Astrophysics Data System (ADS)

In this paper we discuss our approaches and results for the preparation of improved semiconductor quantum dot materials by the sol-gel method. By taking advantage of the low- temperature sol-gel route, the nanostructure and optical properties of CdS quantum dots were greatly improved for device applications. Pore-free sodium borosilicate (NBS) glasses and organically modified silicates (ORMOSILs) were used as matrices for the CdS nanocrystallites. Results from both degenerate four-wave mixing and pump-probe techniques indicated large third-order nonlinear responses of the order of 10-6 esu from CdS-doped NBS glasses. By using potassium ion exchange, the first CdS-doped channel waveguides were fabricated in NBS glasses. Propagation of femtosecond laser pulses through the waveguide was investigated. Pulse breakup effect that may be the result of soliton formation was observed in these waveguides. Polydimethylsiloxane (PDMS) was uses as the organic component to modify the silica gel. CdS-doped ORMOSILs derived from the PDMS- TEOS system exhibits improved mechanical property and film-forming ability compared to purely inorganic gels. Both CdS-doped PDMS-TEOS ORMOSILs and NBS glasses were much more resistant to photodarkening than the glasses made by melting. The use of the bifunctional ligand 3-aminopropyltriethoxysilane (APTES) significantly reduced the average particle size and narrowed the size distribution of CdS quantum dots in silica gels and densified NBS glasses.

Li, Chia-Yen; Kao, Yu-Hua; Hayashi, Kazutaka; Takada, Toshimi; MacKenzie, John D.; Kang, Koo I.; Lee, San-Goo; Peyghambarian, Nasser; Yamane, Masayuki; Zhang, Guang-Wen; Najafi, S. Iraj

1994-10-01

213

Intra-grain composition nonuniform barium strontium calcium titanate ceramics by sol-gel pervasion techniques  

NASA Astrophysics Data System (ADS)

The use of ferroelectric ceramics in microwave devices requires that they possess low-loss, frequency-stable and highly tunable properties. The problems of traditional barium strontium calcium titanate ceramics are higher loss and inappropriate work temperature dependence. In this work, a conventional mixed oxide route was used to prepare BaTiO3, SrTiO3 and CaTiO3 precursor powders. The BaTiO3, SrTiO3 and CaTiO3 powders were thoroughly ball mill mixed. They were then added to 5 wt% polyvinyl alcohol and pressed under a uni-axial pressure of 220 MPa into discs of 12 mm diameter. We introduced nano-grains of barium strontium titanate (BST) into the BSCT ceramic by nano-grain pervasion techniques to fabricate compositionally nonuniform BSCT ceramic samples. The nano-particles of BST are prepared with the sol-gel method. The sol-gel was subjected to ultrasonic irradiation and then vacuum methods in order to easily introduce nanoparticles into bulky BSCT. The ceramics do not show a sharp change in the dielectric constant and have a wide range of Curie temperature distribution. This is attributed to the presence of a compositionally nonuniform micro-area in the samples. Compared with uniform-composition BSCT, compositionally nonuniform BSCT has favourable dielectric properties. These results suggest that the compositionally nonuniform BSCT ceramics are promising candidates as tunable microwave elements.

Xu, Honghai; Jin, Dengren; Wu, Wenbiao; Cheng, Jinrong

2009-03-01

214

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

215

Sol-gel as methodology to obtain bioactive materials.  

PubMed

We employed the sol-gel methodology to obtain a silica matrix modified with calcium and phosphate ions. We prepared the matrix by hydrolysis and condensation of the precursors triethyl phosphate, calcium nitrate, and tetraethylorthosilicate, which were the sources of phosphate, calcium, and silicon, respectively. We dried and heat-treated the samples at 110 or 900°C and placed them in simulated body fluid (SBF) for three days. We conducted scanning electron microscopy, X-ray diffraction, and infrared spectroscopy analyses, which evidenced that the sample treated at 110°C contained calcium phosphate silicate and hydroxyapatite before and after contact with SBF, respectively. The sample treated at 900°C exhibited a hydroxyapatite phase before and after contact with SBF, but the crystalline phase was more evident after the contact. In conclusion, the sol-gel methodology provided bioactive samples for bone regeneration. PMID:24676155

Ribeiro, Thiago J; de Lima, Omar J; Faria, Emerson H; Rocha, Lucas A; Calefi, Paulo S; Ciuffi, Katia J; Nassar, Eduardo J

2014-03-01

216

Sol-gel derived photonic bandgap coatings for solar control  

NASA Astrophysics Data System (ADS)

Sol-gel derived photonic bandgap films have been investigated as possible multilayer coatings for solar control glass applications. Multilayer Bragg mirrors, in particular, have been modelled by the Transfer Matrix method, designed to have either near-UV or near-IR reflectivity, but visible transparency, based on alternating aluminosilicate glass/titania quarter-wave stacks. Such composite multilayer structures have been deposited by sol-gel processing on selected glasses and other types of substrates and their optical characteristics have been measured by optical absorption and reflection spectroscopies, as well as spectroscopic ellipsometry to determine the single layer refractive index and thickness. The UV-visible-IR absorption and reflection characteristics of these multilayer coatings revealed solar control properties, due to the presence of peaks near ˜350-400 nm and ˜900-1000 nm, with reflectivities of the order of 70%, which appear promising for solar control application.

Almeida, Rui M.; Fortes, Luís M.; Clara Gonçalves, M.

2011-10-01

217

AOTF-based remote sensor with sol-gel probe  

SciTech Connect

The authors report the development and application of a sensor using acousto-optic tunable filter (AOTF) and sol-gel probe technology. A pH-sensitive probe is used as a model sensing system with dextran derivatives of pH sensitive dyes doped into sol-gel thin films. They used a unique combination of pH-sensitive and pH-insensitive dual-label dye system. For optimization studies, the performance of these films as a pH sensing probe was evaluated using synchronous fluorescence detection. The performance of the prototype AOTF-based monitor using a low-power argon laser as an ion excitation source was evaluated.

Volkan, M.; Lee, Y.; Vo-Dinh, T.

1999-11-01

218

Superhydrophobic sol-gel nanocomposite coatings with enhanced hardness  

NASA Astrophysics Data System (ADS)

Sol-gel superhydrophobic coatings with improved hardness were prepared by embedding fumed silica nanoparticles in a partially condensed hybrid sol of methyltriethoxysilane (MTEOS) and colloidal silica. Fumed silica particles of size 25-30 nm were incorporated in the sol and the mixture was spray-coated on glass substrate. Water contact angle (WCA) of the composite coating increased with increase in silica content of the sol mixture. The concentration of silica in the sol mixture was optimized to obtain robust superhydrophobic coatings with a WCA of 162.5° and a pencil hardness of 5H. The wetting state of water droplet on the sol-gel composite coatings was analysed with both Wenzel and Cassie-Baxter models.

Lakshmi, R. V.; Bharathidasan, T.; Basu, Bharathibai J.

2011-10-01

219

?-Diketones and their derivatives in sol–gel processes  

NASA Astrophysics Data System (ADS)

Published data on the use of ?-diketones, metal ?-diketonates and some structurally related compounds in sol–gel synthesis of new organic-inorganic hybrid materials are analyzed. Functionalization methods of ?-diketones with carbofunctional organosilicon compounds are considered. Ways of insertion of a metal cation into the organic-inorganic hybrid matrix using non-functionalized ?-diketonates are demonstrated. Particular attention is devoted to luminescent lanthanide derivatives, which is due to the prospects of practical application of materials obtained from them in photonics, integrated optics and medical diagnosis. The types and properties of most widely used sol–gel monomers and oligomers and the luminescence behaviour of lanthanide ?-diketonates and metal-free silica matrices are considered. The bibliography includes 220 references.

Zolotareva, N. V.; Semenov, V. V.

2013-10-01

220

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

221

Nanostructured Energetci Matreials with sol-gel Chemistry  

SciTech Connect

The utilization of nanomaterials in the synthesis and processing of energetic materials (i.e., pyrotechnics, explosives, and propellants) is a relatively new area of science and technology. Previous energetic nanomaterials have displayed new and potentially beneficial properties, relative to their conventional analogs. Unfortunately some of the energetic nanomaterials are difficult and or expensive to produce. At LLNL we are studying the application of sol-gel chemical methodology to the synthesis of energetic nanomaterials components and their formulation into energetic nanocomposites. Here sol-gel synthesis and formulation techniques are used to prepare Fe{sub 2}O{sub 3}/Al pyrotechnic nanocomposites. The preliminary characterization of their thermal properties and the degree of mixing between fuel and oxidizer phases is contrasted with that of a conventional pyrotechnic mixture.

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

2003-11-18

222

Sol-gel-derived PZT fibers: development and limitations  

NASA Astrophysics Data System (ADS)

Fine scale lead zirconate titanate (PZT) fibers were fabricated from sol-gel processed viscous 'sol' using spinning methodology developed for the continuous production of glass and carbon fibers. Subsequent drying and firing at temperatures above 700 degrees Celsius resulted in phase pure perovskite fibers with diameters ranging from 30 to 70 micrometers. The dense fibers were comprised of sub-micron grains at sintering temperatures below 1000 degrees Celsius, growing to 2 - 3 micrometers at 1200 degrees Celsius. The dielectric properties of the sol-gel derived fibers were comparable with that of bulk ceramics for both undoped and modified PZT compositions. Relevant to mechanical properties, however, the fine scale PZT fibers exhibited fracture strengths on the order of 50 MPa, well below that of structural fiber materials, e.g. Al2O3, limiting their potential use in active structural composites.

Meyer, Richard J., Jr.; Yoshikawa, Shoko; Shrout, Thomas R.

1996-02-01

223

Porous olivine composites synthesized by sol–gel technique  

Microsoft Academic Search

Porous LiMPO4\\/C composites (where M stands for Fe and\\/or Mn) with micro-sized particles were synthesised by sol–gel technique. Particles porosity is discussed in terms of qualitative results obtained from SEM micrographs and in terms of quantitative results obtained from N2 adsorption isotherms. Porous particles could be described as an inverse picture of nanoparticulate arrangement, where the pores serve as channels

R. Dominko; M. Bele; M. Gaberscek; M. Remskar; D. Hanzel; J. M. Goupil; S. Pejovnik; J. Jamnik

2006-01-01

224

Nanocrystalline trinitrotoluene (TNT) using sol–gel process  

Microsoft Academic Search

The secondary explosives with superfine particle size have many applications, for example, in synthesizing low vulnerable propellants and explosive bridge wire detonators. We have developed a method for preparation of nanocrystalline trinitrotoluene (TNT) in the silica gel matrix using sol–gel process. The TNT\\/silica xerogels were prepared containing up to 90% TNT and 10% silica. An exothermic peak at around 280°C

S. V. Ingale; P. B. Wagh; R. Tewari; Satish C. Gupta

2010-01-01

225

Synthesis of Silicon Carbide Fibers by Sol-Gel Processing  

Microsoft Academic Search

Silica-phenolic resin hybrid fibers with carbon-to-silicon atomic ratios of 2.6 to 5.4 have been prepared from ethanol solutions of tetraethoxysilane, phenolic resins, water, and hydrochloric acid with a tetraethoxysilane- H2O-HCl molar ratio of 1 : 2 : 0.01 by sol-gel processing. The hybrid fibers have been heated at 1500°C in Ar for carbothermal reduction to convert them into silicon carbide

Isao Hasegawa; Toshiyuki Nakamura; Seiji Motojima; Meisetsu Kajiwara

1997-01-01

226

Development of electrochromic smart windows by sol-gel techniques  

Microsoft Academic Search

A novel nanocomposite lithium ion-conducting electrolyte has been developed, based on organically modified silanes, which is suitable for application in a sol-gel electrochromic system. The system developed consists of FTO-coated (fluorine doped tin oxide) glass coated with tungsten oxide, WO3, at one side of the device as the electrochromic layer, with a cerium oxide-titanium oxide layer, CeO2-TiO2, acting as ion-storage

Brian Munro; S. Kraemer; P. Zapp; Herbert Krug; Helmut K. Schmidt

1997-01-01

227

Phase separation in PMMA\\/silica sol-gel systems  

Microsoft Academic Search

The mechanism of phase separation of sol-gel alkoxy-derived silica systems obtained by acid catalysis in the presence of poly(methyl methacrylate) (PMMA) and tetrahydrofuran was investigated by light scattering. Spinodal decomposition (SD) was confirmed for systems with intermediate PMMA\\/alkoxy compositions occurring with a simultaneous viscosity increase. The initial stages of phase separation followed the linear theory proposed by Cahn. For systems

Kátia Fraga Silveira; Inez Valéria P. Yoshida; Suzana Pereira Nunes

1995-01-01

228

Sol–gel-derived photonic structures: fabrication, assessment, and application  

Microsoft Academic Search

Sol–gel is a handy, very flexible, and cheap method to fabricate, study, and apply innovative photonic structures. The possibility\\u000a of starting from molecular precursors and elementary building blocks permits to tailor structures at the molecular level and\\u000a to create new materials with enhanced performances. Of specific interest for the study of important physical effects as well\\u000a as for application in

Andrea ChiappiniAlessandro; Alessandro Chiasera; Simone Berneschi; Cristina Armellini; Alessandro Carpentiero; Maurizio Mazzola; Enrico Moser; Stefano Varas; Giancarlo C. Righini; Maurizio Ferrari

229

Electrochemical properties of sol-gel deposited vanadium pentoxide films  

Microsoft Academic Search

Microstructure, electrochemical and optical properties of sol-gel deposited vanadium pentoxide (V2O5) coatings were investigated. The films were deposited by spin coating on SnO2:F\\/glass and quartz substrates from a polymeric solution of V2O5 derived from vanadium tri(isopropoxide)oxide. Process parameters were investigated for the deposition of V2O5 films exhititing high lithium insertion capability. Investigations were conducted by cyclic voltammetry, impedance analysis, optical

Nilgün Özer

1997-01-01

230

New developments for sol-gel film and fiber processing  

SciTech Connect

New insights into the development of microstructure in sol-gel films have recently been revealed by several diagnostic techniques, including imaging ellipsometry, {open_quotes}chemical imaging{close_quotes} by fluorescent tracers, light scattering from capillary waves, and finite-element modeling. The evolution of porosity during the continuous transition from dilute sol to porous solid in restricted geometries such as films and fibers is becoming clearer through fundamental understanding of evaporation dynamics and capillarity.

Hurd, A.J.

1995-03-01

231

Transparent conductive sol-gel thin films for photonic applications  

Microsoft Academic Search

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

T. Kololuoma; Juha T. Rantala; Jouko Vahakangas; Risto S. Laitinen

1999-01-01

232

Sol-Gel Derived Barium-Strontium Titanate Films  

Microsoft Academic Search

Sol-gel techniques for the preparation of barium-strontium titanate (BST) films are discussed. The evolution of film microstructure during heat treatment, and the dielectric properties of BST films prepared from alkoxide solutions and from alkoxide solutions modified by 2-ethylhexanoic acid were studied. It is shown that the extent of the modification of the precursors by 2-ethylhexanoic acid changes the precursor molecular

V. A. Vasiljev; K. A. Vorotilov; M. I. Yanovskaya; L. I. Solovjeva; A. S. Sigov

1998-01-01

233

Zinc oxide films prepared by sol–gel method  

Microsoft Academic Search

ZnO films with preferred orientation along the (002) plane were fabricated by the sol–gel method using a spin-coating technique. The effects of annealing process on the microstructure, transparent properties, and morphology of ZnO films were studied. The films which were dried at 300°C and then postheated at 600°C showed the preferred (002) orientation of ZnO and high transmittance above 80%

Hongxia Li; Jiyang Wang; Hong Liu; Huaijin Zhang; Xia Li

2005-01-01

234

Sol–gel preparation and photocatalysis of titanium dioxide  

Microsoft Academic Search

Titanium dioxide (TiO2) is extensively used as a photocatalyst due to the strong oxidizing power of its holes, high photostability and redox selectivity. In the present work, the microstructural and chemical properties of TiO2, obtained by a sol–gel procedure, were investigated. TiO2 sols were prepared by the hydrolysis and condensation of titanium (IV) n-butoxide in iso-propyl alcohol. The particle dimensions

C. Su; B.-Y. Hong; C.-M. Tseng

2004-01-01

235

Sol–gel deposited nickel oxide films for electrochromic applications  

Microsoft Academic Search

The electrochromic (EC) behavior, the microstructure, and the morphology of sol–gel deposited nickel oxide (NiOx) coatings were investigated. The films were produced by spin and dip-coating techniques on indium tin oxide (ITO)\\/glass and Corning glass (2947) substrates.The coating solutions were prepared by reacting nickel(II) 2-ethylhexanoate as the precursor, and isopropanol as the solvent. NiOx was heat treated at 350°C for

E. Ozkan Zayim; I. Turhan; F. Z. Tepehan; N. Ozer

2008-01-01

236

Supported and unsupported sol-gel alumina membranes  

SciTech Connect

Synthetic permselective membranes are useful for many chemical separations. Inorganic membranes have been considered due to their thermal and chemical stability. Sol-gel processing is an attractive method for membrane preparation, because it produces microporous ceramic preforms. In this study, an in-situ sol-gel process was investigated for supported alumina membranes, and a two-step sol-gel process was investigated for unsupported alumina membranes. Aluminum sec-butoxide (ASB) was used as the precursor. XRD, thermal analysis, FTIR, SEM, TEM, nitrogen adsorption/desorption analysis, and gas permeation measurements were the basic techniques used for membrane characterization. Supported alumina membranes were synthesized by attaching an alumina gel layer to the outside of a porous alumina tube. An in-situ sol-gel coating technique, involving the permeation of water through the tube wall to control the rate of hydrolysis, was developed. Three different approaches, referred to as flowing water approach, complete wetting approach, and partial wetting approach, were studied for delivering the water. Isopropanol was the best solvent compared with ethanol and butanol. By diluting ASB with isopropanol in a 1:25 volume ratio, an optimum reactivity was found that allowed a gel layer to grow which could remain intact throughout drying. A multistep drying procedure was established. The gel coating was adherent and insoluble in water. It followed the contour of the supporting surface, and withstood light abrasion. The coating remained effective after 800[degrees]C firing. Unsupported alumina membranes were synthesized by casting an alumina sol, generated in a two-step process, onto polystyrene petri dishes. Drying conditions for the gel sheets were optimized. The gel sheets were dried and heated without warping or cracking. The membranes of 80 microns thickness could support a pressure differential of 1 atm.

Yu, C.

1992-01-01

237

Microwave-enhanced densification of sol–gel alumina films  

Microsoft Academic Search

Alumina films prepared by the sol–gel method were sintered at 1160 °C and 1200 °C using a 2.45 GHz microwave\\/conventional hybrid furnace in order to study the influence of microwave power on the sintering process and resultant samples. Experiments were designed to ensure that each series of samples underwent an identical thermal history in terms of temperature\\/time profiles. Sintering was carried out using

Jianxin Wang; Jon Binner; Yongxin Pang; Balasubramaniam Vaidhyanathan

2008-01-01

238

Pressureless sintering of sol–gel alumina matrix composites  

Microsoft Academic Search

The effect of the temperature and the conditions of the reducing atmosphere on the sintering behaviour of pressureless-sintered sol–gel alumina matrix composites are studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and density measurements. The results are compared with those obtained with fine commercial alumina\\/SiCW composites, and analyzed by means of a thermodynamic study of the system.A notable improvement

G. Urretavizcaya; J. M. Porto Lopez; A. L. Cavalieri

2000-01-01

239

Seeded sol-gel derived alumina-zirconia composites  

Microsoft Academic Search

The effect of ?-alumina seed particles on the densification and microstructure development of the sol-gel derived alumina-zirconia composites has been studied. The alumina-zirconia sols have been prepared from two different alumina sols (polymer and particulate) and two different types of zirconia particles. Addition of the seed particles decreases the ? to ?-alumina transformation temperature by more than 100 °C and

Vladimir Srdi?; Ljiljana Radonji?

1995-01-01

240

Synthesis and characterization of sol–gel alumina nanofibers  

Microsoft Academic Search

\\u000a Abstract  Alumina nanofibers of high aspect ratio with surface area of >300 m2 g?1 has been prepared successfully in bulk quantities by the sol–gel method. The synthesis parameters including the binary water–alcohol\\u000a solvent system to aluminium isopropoxide ratio, pH, type of solvent and aging temperature affect the uniformity and formation\\u000a of nanofibers. It is proposed that alumina nanofibers were formed by the curling

Geik Ling Teoh; Kong Yong Liew; Wan A. K. Mahmood

2007-01-01

241

Grinding of sol-gel derived alumina-zirconia composites  

Microsoft Academic Search

Alumina-zirconia powders containing 12.5 wt% zirconia were prepared by sol-gel processing. After calcination these powders were cold pressed, sintered and HIPed. The maximum amount of tetragonal form of zirconia is retained in these specimens. Grindability and the transformation behaviour of tetragonal zirconia were evaluated by conducting grinding studies at different speeds and depths of cut. The surface characteristics of the

M. Balasubramanian; T. Sornakumar; S. K. Malhotra; C. V. Gokularathnam; R. Krishnamurthy

1995-01-01

242

Sol-gel route to very high porosity silica aerogels.  

National Technical Information Service (NTIS)

This report discusses the preparation and characterization of very high porosity silica aerogels. The data presented here suggests a microstructure for the very high porosity silica aerogel that differs from the bead-like structure proposed for single-ste...

L. W. Hrubesh T. M. Tillotson J. F. Poco

1991-01-01

243

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

244

Sol-gel-based biosensor for use in stroke treatment.  

PubMed

A fiber optic biosensor for the detection of fibrinolytic products produced during lysis of "soft" blood clots is described. The biosensor was constructed to be selective toward D dimer antigens, which form from the dissolution of cross-linked fibrin clots. The presence of D dimer antigens above a threshold level is a clinical diagnostic used to determine the presence of such occlusions following a stroke. Fluorescein-labeled D dimer antibodies are immobilized on the tip of an optical fiber by dip coating from a silica sol-gel solution. When D dimer antigens combine with the antibodies, fluorescence intensity decreases. The response of the sensor was examined in phosphate buffered saline, human plasma, and blood. Calibration plots for the sensor were obtained in the clinically significant D dimer concentration range from 0.54 microgram/ml to 6 micrograms/ml. Changes in spectroscopic properties as the sol-gel encapsulated tagged antibodies aged were examined; a decrease in fluorescence intensity with age was noted. The D dimer antibodies remain viable for at least 4 weeks while encapsulated in the sol-gel network when stored at 4 degrees C in PBS solution. This novel sensor is being developed for use with other catheter-based microtools to treat stroke resulting from occlusion in the vascular system. PMID:10513125

Grant, S A; Glass, R S

1999-10-01

245

Synthesis of phthalocyanine doped sol-gel materials  

NASA Technical Reports Server (NTRS)

The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross section ratio, 4, however, the tetrasulfonate groups make the dye soluble in water which greatly facilitates its incorporation into the sol-gel matrix. The nonlinear transmission of CuPc4S in a pH 2 buffer solution and in a silica xerogel were compared. It is evident that the CuPc4S preserves its optical limiting behavior in the sol-gel matrix, indicating that the fundamental excited state absorption process is essentially the same for a molecule in solution or in the solid state. Although the spectroscopic details of energy level lifetimes are unknown, the significance is that passive optical limiting has been achieved in the solid state via incorporation of a dye into an inorganic host. The only compromise occurs at the extremely high energy regime where photobleaching is observed. This is a result of the limited mobility of the dye molecules in the solid silica host relative to a liquid host. The effects of photodegradation in the xerogel are additive, whereas the solution provides a supply of fresh molecules that are free to enter the active volume between pulses.

Dunn, Bruce

1993-01-01

246

Effect of stabilizer on structural, optical and electrochemical properties of sol–gel derived spin coated TiO 2 films  

Microsoft Academic Search

Thin films of TiO2 were prepared using two different sol–gel routes. The two routes employed diethanolamine (DEA) and acetylacetone as stabilizing agents with titanium isopropoxide (Ti(OPri)4) in ethanol as the deposition solution. The densification at 500°C achieved the nanophase TiO2 films, which were investigated by performing structural, optical and electrochemical studies. Ion storage capacity and transmission measurements showed superior response

Amita Verma; S. B. Samanta; A. K. Bakhshi; S. A. Agnihotry

2005-01-01

247

A comparative study of microstructural development in the sol–gel derived alumina–mullite nanocomposites using colloidal silica and tetraethyl orthosilicate  

Microsoft Academic Search

This paper compares the microstructure development of two alumina–15 vol% mullite composites during the sintering. The nanopowders\\u000a of alumina–mullite composite were synthesized by the sol–gel method using aluminum chloride hexahydrate and two different\\u000a silicon sources (colloidal silica in route 1 and tetraethyl orthosilicate in route 2). The alumina–mullite composites were\\u000a prepared by pressing and sintering of the nanopowders. Although the

A. Sedaghat; E. Taheri-Nassaj; G. D. Soraru; T. Ebadzadeh

2011-01-01

248

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

249

Silica sol–gel immobilized amperometric biosensor for the determination of phenolic compounds  

Microsoft Academic Search

An amperometric enzyme electrode for phenolic compounds was developed via an easy and effective immobilization method using the sol–gel technique. The enzyme electrode comprises tyrosinase immobilized by the thin silica sol–gel layer on a carbon-paste electrode. The tyrosinase retains its bioactivity when being immobilized by the sol–gel film. Phenolic compounds were determined by the direct reduction of biocatalytically liberated quinone

J. Li; L. S. Chia; N. K. Goh; S. N. Tan

1998-01-01

250

Corrosion inhibition of magnesium by combined zirconia silica sol–gel films  

Microsoft Academic Search

The inhibition of Mg (AZ91D) corrosion by thin sol–gel films was studied. The sol–gel films were prepared by the traditional acid or base-catalyzed hydrolysis and condensation, and finally deposited by dip coating. Two different sol–gel monomers were used: phenyltrimethoxysilane (PTMOS) and zirconium(IV)tetra-1-propoxide (ZrTPO). Films were made of each of the individual monomers and by depositing first a PTMOS film followed

Yair Tamar; Daniel Mandler

2008-01-01

251

Nitric oxide-releasing sol?gels as antibacterial coatings for orthopedic implants  

Microsoft Academic Search

To assess the benefits of nitric oxide (NO)-releasing sol-gels as potential antibacterial coatings for orthopedic devices, medical- grade stainless steel is coated with a sol-gel film of 40% N-aminohexyl-N-aminopropyltrimethoxysilane and 60% isobutyl- trimethoxysilane. Upon converting the diamine groups in these films to diazeniumdiolate NO donors, the NO release from the sol- gel-coated stainless steel is evaluated at both ambient and

Brian J. Nablo; Aaron R. Rothrock; Mark H. Schoenfisch

2004-01-01

252

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

Microsoft Academic Search

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

Mial E. Warren; Matthew Farrow; Alexander Smith Tappan

2009-01-01

253

Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes  

SciTech Connect

Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-04-04

254

Thick ceramic coatings using a sol gel based ceramic-ceramic 0–3 composite  

Microsoft Academic Search

A sol gel based coating technology has been developed for making high quality, thick ceramic coatings. The films are ceramic-ceramic 0–3 composites made by dispersing ceramic powders in a sol gel solution. The resulting system has all the benefits of sol gel, i.e. ease of fabrication, ability to coat complex geometries and relative cost effectiveness, but is not limited in

D. A. Barrow; T. E. Petroff; M. Sayer

1995-01-01

255

Inorganic-organic nanocomposites based on sol-gel derived magnesium fluoride.  

PubMed

Monodispersed magnesium fluoride nanoparticles are utilized for the first time to prepare transparent inorganic-organic nanocomposite materials with improved mechanical properties. The fluorolytic sol-gel synthesis route has been modified for the preparation of monodispersed magnesium fluoride nanoparticles with a size of 2-3 nm. MgF(2) particles are effectively stabilised against agglomeration by phosphonic acids, which strongly bind to the particles and lead to an increased compatibility of the inorganic particles with the organic polymers. This way, highly transparent nanocomposite materials with up to 20 wt% magnesium fluoride in different acrylates are obtained, featuring high dispersion of MgF(2) particles in the polymer matrix and an increased hardness by the factor of 2. The nature of interaction between phosphonic acids and magnesium fluoride is thoroughly investigated by IR and NMR showing a monodentate coordination of phosphonates to the particle's surface. PMID:21989714

Noack, Johannes; Schmidt, Larissa; Gläsel, Hans-Jürgen; Bauer, Monika; Kemnitz, Erhard

2011-11-01

256

Optimized droplet-based microfluidics scheme for sol-gel reactions.  

PubMed

A droplet-based microfluidic reaction scheme is developed where the chemical reactants are dispensed with precise volume control into pairs of droplets. The reaction is activated by coalescing droplet pairs and fast mixing inside the coalesced droplets. Furthermore, the pre-processing of the chemical products is included in the microfluidic device. This reaction scheme allows the performing of precisely volume controlled reactions and long operation times without any clogging even if precipitates or sticky gels are formed during the reaction. Using this approach and optimizing the reaction parameters, we generate mesoporous silica microspheres from a rapid gelation optimized sol-gel synthesis route. The produced silica particles have a superior surface area of 820 m(2) g(-1) and a narrow pore radius distribution of around 2.4 nm. PMID:20405061

Chokkalingam, Venkatachalam; Weidenhof, Boris; Krämer, Michael; Maier, Wilhelm F; Herminghaus, Stephan; Seemann, Ralf

2010-07-01

257

Study on process development and property evaluation of sol-gel derived magnesia stabilized zirconia minispheres  

NASA Astrophysics Data System (ADS)

In order to overcome limitations in the processing parameters of powder compaction method, a novel processing technique based on sol-gel route has been developed to produce near-net-shaped prototype fine zirconia minispheres with required properties that could potentially be used as grinding media. Impact of magnesia concentration and sintering temperature on the final product has been analyzed in detail. Zirconia minispheres have been characterized to establish a correlation between physical, structural and mechanical properties. Sintering temperature, soaking period, heating rate and viscosity of the sol apparently influence the characteristics of the magnesia stabilized zirconia minispheres. The phase identification, density variation, chemical decomposition, functional group specification, surface area, porosity, shrinkage and microstructural features of the dried and sintered final product have been studied. It has been observed that magnesia content, sintering temperature, density and the grain size of the sintered minispheres have a significant impact on the mechanical properties of the final product.

Judes, J.; Kamaraj, V.

2014-05-01

258

Sol-gel derived porous bioactive nanocomposites: Synthesis and in vitro bioactivity  

NASA Astrophysics Data System (ADS)

Porous bioactive composites consisting of SiO2-CaO-Na2O-P2O5 bioactive glass-ceramic and synthetic water soluble polymer Polyvinylpyrrolidone [PVP (C6H9NO)n, MW~40000 g/mol] have been synthesized by sol-gel route. As-prepared polymeric composites were characterized by X-ray diffraction (XRD) technique. Two major bone mineral phases, viz., hydroxyapatite [Ca10(PO4)6(OH)2] and wollastonite [calcium silicate (CaSiO3)] have been identified in the XRD patterns of the composites. Presence of these bone minerals indicates the bioactive nature of the composites. In vitro bioactivity tests confirm bioactivity in the porous composites. The flexibility offered by these bioactive polymer composites is advantageous for its application as implant material.

Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

2013-06-01

259

Sol-gel silica platforms for microalgae-based optical biosensors.  

PubMed

An advanced hybrid biosensing platform with improved optical quality is developed based on the acidic encapsulation of microalgi in silica matrices synthesized by TAFR (tetraethoxysilane derived alcohol free route). The three microalgi (Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii) were previously immobilized in alginate following the two-step procedure. Tuning the alginate protecting function with the aid of Tris-HCl buffer, the sol-gel synthesis was conducted at pH 4.0 well below the tolerance limit imposed by the encapsulated microalgae. The acidic condensation of Si(IV) generates silica matrices with outstanding optical properties that suit the requirements of biosensors based on optical detection methods. PMID:24637376

Perullini, Mercedes; Ferro, Yannis; Durrieu, Claude; Jobbágy, Matías; Bilmes, Sara A

2014-06-10

260

Sol-gel processes and materials. (Latest citations from the Aerospace database). Published Search  

SciTech Connect

The bibliography contains citations concerning design and development of sol-gel processes and sol-gel derived materials. Sol-gel derived materials include protective and transparent films, ceramic coatings, nanocomposites and microcomposites, porous and dense composites, fiber reinforced composites, oxides, and ductile ceramics. Topics include preparation of high temperature superconducting oxides and films, glass-ceramic composites and ceramic matrix composites for high temperature applications, sol-gel processes for advanced ceramics, coatings on semiconductors, infrared optical coatings, and coatings on carbon/carbon composites. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1994-11-01

261

Introducing hydrophilic carbon nanoparticles into hydrophilic sol-gel film electrodes  

Microsoft Academic Search

A hydrophilic carbon nanoparticle–sol-gel electrode with good electrical conductivity within the sol-gel matrix is prepared.\\u000a Sulfonated carbon nanoparticles with high hydrophilicity and of 10–20 nm diameter (Emperor 2000) are co-deposited onto tin-doped\\u000a indium oxide substrates employing a sol-gel technique. The resulting carbon nanoparticle-sol-gel composite electrodes are\\u000a characterized as a function of composition and salt (KCl) additive. Scanning electron microscopy and voltammetry

Stuart M. Macdonald; Katarzyna Szot; Joanna Niedziolka; Frank Marken; Marcin Opallo

2008-01-01

262

In vitro cytotoxicity of nitric oxide-releasing sol–gel derived materials  

Microsoft Academic Search

The cytotoxicity of bare and PU-coated nitric oxide (NO)-releasing sol–gel derived materials (sol–gels) was investigated using L929 mouse fibroblasts in both direct and indirect contact models to differentiate between the biological impact of the sol–gel matrix and NO release. The flux of NO was varied up to 150pmolcm?2s?1 using N-(6-aminohexyl)-aminopropyltrimethoxysilane (balance iso-butyltrimethoxysilane) diazeniumdiolate (NO donor)-modified sol–gels. The addition of a

Brian J. Nablo; Mark H. Schoenfisch

2005-01-01

263

Silver nanocrystals in silica by sol-gel processing  

Microsoft Academic Search

Silver nanocrystal doped silica films were prepared by the sol-gel process. The sol was prepared from 1:0.12:12:0.2:6:7 molar ratios of Si(OC2H5)4:AgNO3:H2O:HNO3:C3nH7OH:C4iH9OH. The glassy, highly transparent film with high dopant concentration (silver\\/silicon atomic ratio = 0.12) was successfully prepared by the dip-coating method. After drying in air at 60°C for 30 min, samples were heat-treated, in air, at 300, 350, 400,

G. de; A. Licciulli; C. Massaro; L. Tapfer; M. Catalano; G. Battaglin; C. Meneghini; P. Mazzoldi

1996-01-01

264

Guided wave measurements for characterization of sol-gel layers  

NASA Astrophysics Data System (ADS)

Sol-gel applications require very thick layers with a good understanding of the interfaces. To address this problem, we have installed at CEA Le Ripault a characterization bench using guided waves with assistance from the IM2NP lab in Marseille. This bench allows us to measure the thickness and the refractive index and determine the extinction coefficient of a thin layer. We can distinguish losses at interfaces from those in the bulk according to the chosen propagation mode. This allows us to know if we can stack elementary layers to make thick layers without incurring problems.

Piombini, Hervé; Dieudonne, Xavier; Wood, Thomas; Flory, François

2013-09-01

265

Synthesis of silicon carbide fibers by sol-gel processing  

Microsoft Academic Search

Silica-phenolic resin hybrid fibers with carbon-to-silicon atomic ratios of 2.6 to 5.4 have been prepared from ethanol solutions\\u000a of tetraethoxysilane, phenolic resins, water, and hydrochloric acid with a tetraethoxysilane-H2O?HCl molar ratio of 1:2:0.01 by sol-gel processing. The hybrid fibers have been heated at 1500C in Ar for carbothermal reduction\\u000a to convert them into silicon carbide fibers. The effects of the

Isao Hasegawa; Toshiyuki Nakamura; Seiji Motojima; Meisetsu Kajiwara

1997-01-01

266

Wrinkling of a sol-gel-derived thin film  

NASA Astrophysics Data System (ADS)

We report on the wrinkle formation in a thin film produced by the sol-gel method. Through the relaxation of stress, which results from the removal of the solvent during the drying process, an isotropic wavy pattern is generated in the form of skeletal branches. The patterns have a dominant wavelength satisfying a relationship of three-fourths order of thickness. Densification of the gelated film is enhanced by an increase in the volumetric strain caused by the evaporation of the remaining solvent from the film. The number of skeletal branches and surface roughness increases as the annealing time progresses, without any change in the skeletal wavelength.

Kwon, S. Joon; Park, Jae-Hwan; Park, Jae-Gwan

2005-01-01

267

Preparation of superhydrophobic surface with a novel sol-gel system  

NASA Astrophysics Data System (ADS)

Sol-gel method is a simple and cheap way to prepare superhydrophobic coatings or films, however, most of the researches on sol-gel focus on silica or ZnO sol-gel. The present paper proposes a novel sol-gel which is made from hydrolysis and condensation of the by-product of polymethylhydrosiloxane (PMHS) reacting with ?-aminopropyltriethoxysilane (KH550). The mechanism of formation of the by-product and the sol-gel is discussed and the by-product is characterized by FT-IR. The mass ratio of KH550/PMHS of the sol-gel influences the water contact angle (WCA) and water sliding angle (WSA) of the film made of spraying the sol-gel to microscope glass. When the mass ratio of KH550/PMHS of the sol-gel reaches 0.25, WCA of the corresponding film is 157° and WSA of it is less than 1°. The mechanism of formation of the sol-gel is discussed, and the size of the sol-gel is characterized by polarization microscope as well. The morphology of the film made of the sol-gel is analyzed by means of scanning electron microscope (SEM). It was found that the diameter of the particle of the superhydrophobic film is about 40 ?m, nevertheless, from the larger magnification picture, the particle is found to be composed of micro-balls whose diameter is about 2 ?m, and the micro-ball is composed of nano-sphere whose diameter is less than 200 nm.

Su, Dong; Huang, Chengya; Hu, You; Jiang, Qiangwei; Zhang, Long; Zhu, Yunfeng

2011-11-01

268

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

269

Granulation of sol-gel-derived nanostructured alumina  

SciTech Connect

A sol-gel granulation process was developed to prepare porous nanostructured {gamma}-alumina granules as supports for catalysts and adsorbents. The process, which starts with an aqueous sol of gelatinous boehmite, involves droplet formation, gelation in paraffin oil, conditioning in ammonia solution, and drying and calcination in air under controlled conditions. The {gamma}-Al{sub 2}O{sub 3} granules prepared are 1--3 mm-dia. spherical particles with large surface area (380 m{sup 2}/g) and pore volume (0.5 cm{sup 3}/g), uniform pore-size distribution (20--60 {angstrom}), and controllable average pore size (35 {angstrom}). These sol-gel-derived granules have excellent mechanical properties with crush strength (>100 N per granule) and attrition resistance (<0.01 wt.%/h), much better than the commercial alumina and zeolite granules. Supported CuO sorbents were prepared on these granules for SO{sub 2} removal applications. The alumina-supported CuO sorbents contain higher loading of well-dispersed CuO and better sulfation properties than similar sorbents reported in the literature.

Deng, S.G.; Lin, Y.S. [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering] [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering

1997-02-01

270

Comparaison entre les Procedes Sol-Gel de la Zircone et de l'Alumine (Comparison of Sol-Gel Procedures for Zircon and Alumina).  

National Technical Information Service (NTIS)

Zirconium and aluminum oxide sol-gel procedures are reviewed. Published results are presented, including both the physical and chemical aspects of the procedures. The differences in zircon and alumina behavior are explained. It is concluded that for both,...

A. C. Pierre

1988-01-01

271

Sol-gel based oxidation catalyst and coating system using same  

NASA Technical Reports Server (NTRS)

An oxidation catalyst system is formed by particles of an oxidation catalyst dispersed in a porous sol-gel binder. The oxidation catalyst system can be applied by brush or spray painting while the sol-gel binder is in its sol state.

Watkins, Anthony N. (Inventor); Leighty, Bradley D. (Inventor); Oglesby, Donald M. (Inventor); Patry, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor)

2010-01-01

272

Control of Dopant Adsorption from Aqueous Solution into Nanoporous Sol-Gel Films  

Microsoft Academic Search

The doping of porous sol-gel films by adsorption of cations onto silica from aqueous solutions is demonstrated. The films are fabricated using the sol-gel method, giving nanometer scale porosity, high surface area, and homogeneity on the scale of optical wavelengths. After deposition by spin coating and initial heat treatment, the films are soaked in a salt solution of the desired

O. McCARTHY; E. M. YEATMAN

1998-01-01

273

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

274

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

NASA Astrophysics Data System (ADS)

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

1995-04-01

275

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

276

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

277

A novel approach to synthesis of nanosize MgAl 2O 4 spinel powder through sol–gel citrate technique and subsequent heat treatment  

Microsoft Academic Search

This paper summarizes a study on the influence of heat-treatment atmosphere in synthesis of nanosize MgAl2O4 spinel powder employing sol–gel citrate route. Based on measurement of BET specific surface area, crystallite size, simultaneous thermal analysis, and microscopic observation, it was clarified that the argon atmosphere used for heat treatment of precursor reduced the particle size of synthesized ceramic powder significantly.

Ali Saberi; Farhad Golestani-Fard; Monika Willert-Porada; Zahra Negahdari; Christian Liebscher; Benjamin Gossler

2009-01-01

278

Photocatalytic oxidation of methyl ethyl ketones over sol–gel mesoporous and meso-structured TiO 2 films obtained by EISA method  

Microsoft Academic Search

This work reports the influence of the meso-structure of TiO2 films in the photocatalytic oxidation of methyl ethyl ketone. Five types of TiO2 films were prepared combining the sol–gel route with the Evaporation Induced Self-Assembly (EISA) method. Sols were prepared from titanium tetrachloride (TiCl4) using different types of pore generating agents. Films characterisation was performed by Fourier Transform Infrared Spectroscopy

N. Arconada; Y. Castro; A. Durán; V. Héquet

2011-01-01

279

Synthesis of A novel aminoalkoxide of iron by oxide one-pot process: Its sol-gel application to iron oxide powder  

Microsoft Academic Search

A low-cost and facile route to synthesize ferratrane complex, which can be employed as alkoxide precursor for iron oxide or doped iron oxide via sol-gel technique, has been developed from the reaction of a very inexpensive and plentiful starting materials via the oxide one-pot synthesis (OOPS) process. Ferratrane complex was directly synthesized from iron hydroxide, triethanolamine and ethylene glycol in

Manop Panapoy; Chutaporn Duangdee; Apirat Laobuthee; Bussarin Ksapabutr

280

Effect of different fuels on the strontium hexaferrite nanopowder synthesized by a surfactant-assisted sol–gel auto-combustion method  

Microsoft Academic Search

In this research a sol–gel auto-combustion route has been proposed to synthesize strontium hexaferrite nanopowder, using metal nitrates, ammonia as pH adjusting agent, n-decyltrimethylammonium bromide as a cationic surfactant and different fuels such as citric acid, glycine, acetylacetone and oxalic acid. The formation temperature of strontium hexaferrite and its crystallite size in presence of different fuels were compared together. The

M. Ghobeiti Hasab; S. A. Seyyed Ebrahimi; A. Badiei

2007-01-01

281

Controlled deposition of sol-gel sensor material using hemiwicking  

NASA Astrophysics Data System (ADS)

Optical sensors are fabricated by depositing liquid sol-gel sensor material on a polycarbonate surface, which has been decorated with arrays of periodic micropillars. Using the principle of hemiwicking, the liquid material is spread, guided by the surface structures, to homogeneously fill the volume between the surface structures and form a liquid film with a thickness determined by the height of the micropillars. After evaporation of solvents, a uniform layer of sensor material resides on the surface. This fabrication method enables easy and reproducible deposits of isolated spots of different sensor materials of precise thickness to be made on plastic surfaces, and it provides an improved method for fabricating cheap optical sensors integrated in disposable lab containers.

Mikkelsen, Morten Bo; Marie, Rodolphe; Hansen, Jan H.; Wencel, Dorota; McDonagh, Colette; Nielsen, Hans Ole; Kristensen, Anders

2011-11-01

282

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

283

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

284

Manufacture of Regularly Shaped Sol-Gel Pellets  

NASA Technical Reports Server (NTRS)

An extrusion batch process for manufacturing regularly shaped sol-gel pellets has been devised as an improved alternative to a spray process that yields irregularly shaped pellets. The aspect ratio of regularly shaped pellets can be controlled more easily, while regularly shaped pellets pack more efficiently. In the extrusion process, a wet gel is pushed out of a mold and chopped repetitively into short, cylindrical pieces as it emerges from the mold. The pieces are collected and can be either (1) dried at ambient pressure to xerogel, (2) solvent exchanged and dried under ambient pressure to ambigels, or (3) supercritically dried to aerogel. Advantageously, the extruded pellets can be dropped directly in a cross-linking bath, where they develop a conformal polymer coating around the skeletal framework of the wet gel via reaction with the cross linker. These pellets can be dried to mechanically robust X-Aerogel.

Leventis, Nicholas; Johnston, James C.; Kinder, James D.

2006-01-01

285

Novel electrochemical materials prepared by sol-gel chemistry  

SciTech Connect

Past efforts in this program have been devoted to exploring the preparation, properties, and structures of various beta alumina compositions in which the mobile sodium ion content was replaced with a variety of divalent and trivalent cations. Though this line of work has produced a great number of new and unusual materials, in particular unusual solid electrolytes and new optical materials, as well as insight into the factors which control fast ion transport in solids, it seemed an appropriate time to move on to another topic. So, over the past year, most of the effort in this program has been devoted to investigations of the use of sol-gel chemistry to produce unusual electrochemical materials, such as solid state ionic conductors, new high rate cathode materials, and unusual organic-inorganic composite materials.

Farrington, G.C.; Thomas, J.O.; Friberg, S.

1993-05-31

286

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

287

Electrochromism in sol-gel deposited TiO2 films  

NASA Astrophysics Data System (ADS)

Electrochromism is sol-gel deposited TiO2 films and films containing TiO2 and WO3 has been observed. The films are deposited by dip-coating from a precursor containing titanium isopropoxide in ethanol or titanium propoxide in ethanol, and after deposition the films are heat treated to between 250 degree(s)C and 300 degree(s)C. The films do not show any signs of crystallinity. However substantial coloration is observed using Li+ ions in a non-aqueous electrolyte, both in pure TiO2 films and in mixed metal oxide films (WO3:TiO2), although the voltage required to produce coloration is different in the two cases. Results will be presented detailing the optical switching and charge transport properties of the films during cyclic voltammetry. These results will be used to compare the performance of the TiO2 films with other electrochromics. The TiO2 and mixed metal films all color cathodically, and the colored state is a neutral greyish color for TiO2, while the bleached state is transparent and colorless, Results on coloration efficiency and the stability under repeated electrochemical cycling will also be presented. The neutral color of the TiO2 films and mixed-metal films means that electrochromic windows based on TiO2 may have significant advantages over WO3-based windows. A detailed analysis of the optical properties of the colored state of the films will be presented. The dynamics of coloration for these films is also under investigation, and preliminary results will be presented.

Bell, John M.; Barczynska, Joanna; Evans, L. A.; MacDonald, Kathleen A.; Wang, J.; Green, David C.; Smith, Geoffrey B.

1994-09-01

288

Titania-silica mixed oxides. V. Effect of sol-gel and drying conditions on surface properties  

SciTech Connect

Mesoporous titania-silica aerogels have been prepared by an alkoxide-sol-gel process with ensuing supercritical drying which involved either semicontinuous extraction using supercritical CO{sub 2} or transferring the solution-sol-gel liquid directly into the super-critical state. Surface properties of these materials were compared to those of conventionally dried titania-silica xerogel. The influence of several important preparation parameters (hydrolysis route, Ti-content, and drying method) on surface properties of the gels were investigated by temperature-programmed reaction and desorption (TPRD) of isopropanol and X-ray photoelectron spectroscopy (XPS). The information gained by these surface-sensitive methods was interpreted in the light of previous bulk structural investigations, i.e., X-ray diffraction, FTIR, FTRaman, and UV-vis spectroscopy. Up to 723 K, three TPRD peaks were identified and assigned to the different surface species in titania-silica mixed oxides found in previous structural investigations: inactive silica domains, titania domains, and highly dispersed Ti in silica (Si-O-Ti linkages). The Ti-containing surface species catalyzed dehydration of isopropanol to propene at different temperatures. Depending on the dispersion and nature of titanium oxo species on the surface of the titania-silica sol-gel mixed oxides (Si-O-Ti heteroconnectivity), significant differences in the reaction-desorption profiles were observed. All titania-silica gels showed enrichment of the surface with silica. This behavior strongly depended on the drying procedure applied. Low-temperature supercritical drying and evaporative drying yielded higher titania surface concentration (lower Si enrichment) compared to high-temperature supercritical drying. 23 refs., 8 figs.

Dutoit, D.C.M.; Goebel, U.; Schneider, M.; Baiker, A. [Swiss Federal Inst. of Technology, Zurich (Switzerland)] [Swiss Federal Inst. of Technology, Zurich (Switzerland)

1996-12-01

289

Nitric oxide-releasing sol-gels as antibacterial coatings for orthopedic implants.  

PubMed

To assess the benefits of nitric oxide (NO)-releasing sol-gels as potential antibacterial coatings for orthopedic devices, medical-grade stainless steel is coated with a sol-gel film of 40% N-aminohexyl-N-aminopropyltrimethoxysilane and 60% isobutyltrimethoxysilane. Upon converting the diamine groups in these films to diazeniumdiolate NO donors, the NO release from the sol-gel-coated stainless steel is evaluated at both ambient and physiological temperature. Sol-gel films incubated at 25 degrees C have a lower NO flux over the first 24 h compared to those at 37 degrees C, but release more than five times longer. The bacterial adhesion resistance of NO-releasing coatings is evaluated in vitro by exposing bare steel, sol-gel, and NO-releasing sol-gel-coated steel to cell suspensions of Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis at 25 degrees C and 37 degrees C. Cell adhesion to bare and sol-gel-coated steel is similar, while NO-releasing surfaces have significantly less bacterial adhesion for all species and temperatures investigated. PMID:15353203

Nablo, Brian J; Rothrock, Aaron R; Schoenfisch, Mark H

2005-03-01

290

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

PubMed

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals--including noble metals--to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm(-1). This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices. PMID:22426457

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

2012-05-01

291

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

SciTech Connect

Nanostructured mesoporous CuO/{gamma}-Al{sub 2}O{sub 3} granular sorbents were prepared by the sol-gel method. Performance of the sol-gel-derived CuO/{gamma}-Al{sub 2}O{sub 3} sorbents for SO{sub 2} removal was studied in a fixed-bed adsorption system. SO{sub 2} breakthrough curves with a feed stream of air containing 2000 ppm SO{sub 2} 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 temperature on the sol-gel-derived sorbent was found to be 400 C. The properties of the sol-gel-derived sorbents are compared with a similar sorbent from a commercial source used in the pilot-scale copper oxide flue gas desulfurization process. At high temperatures (>400 C) the sol-gel-derived CuO sorbents exhibit catalytic properties for converting SO{sub 2} to SO{sub 3}. The crush strength of the sol-gel-derived sorbents is about 5 times that of the commercial sample, while the attrition rate of the former is about 4--10 times smaller than the latter. The SO{sub 2} sorption capacity of the sol-gel-derived sorbent is about 3 times that of the commercial sorbent with a similar amount of CuO loading. The better mechanical properties and higher sulfation capacity of the sol-gel-derived alumina-supported copper oxide sorbents are due to their unique microstructure and the method used for coating CuO. The sulfation and regeneration study shows good regenerability and stability of the sol-gel-derived CuO/{gamma}-Al{sub 2}O{sub 3} sorbents.

Wang, Z.M.; Lin, Y.S. [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering] [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering

1998-12-01

292

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

293

Nanostructured scintillating optical fiber prepared via sol-gel technique for detecting gamma radiation.  

PubMed

An innovative scintillating material prepared through distributing cesium iodide (CsI) nanocrystals into pores of a transparent nanoporous silica using a sol-gel technology has been developed. The CsI nanocrystals doped porous silica material has been designed and made into an optical fiber by using a patented sol-gel technique. This CsI-doped sol-gel silica optical fiber was conveniently connected to a highly sensitive photon detector in testing the material for detecting gamma radiation. The preliminary test result reported in this Letter clearly demonstrates the feasibility of this scintillating fiber for detecting high-energy radiations. PMID:19838287

Tao, Shiquan; Jayaprakash, Ashwini

2009-10-15

294

Hydrothermal processing of barium strontium titanate sol-gel composite thin films  

Microsoft Academic Search

Stoichiometric barium strontium titanate (BST) films of composition \\u000a $${\\\\rm Ba}_{0.7}{\\\\rm Sr}_{0.3}{\\\\rm TiO}_{3}$$\\u000a with thickness >2 ?m have been fabricated on Si\\/SiO2\\/Pt substrates by hydrothermal sol-gel composite processing. This film deposition technique involves the treatment of a spun-on\\u000a sol-gel composite film, formed from a suspension of a powder in an aqueous BST sol-gel, at temperatures from 100–200°C at\\u000a a pressure of

K. Zelonka; M. Sayer; A. P. Freundorfer; J. Hadermann

2006-01-01

295

Photosensitive sol-gel waveguides on silicon substrates as MOEM devices  

NASA Astrophysics Data System (ADS)

Integrated optical components formed by sol-gel process and MEMS devices created on silicon substrate can be used to realize different types of sensing elements for smart structure applications. In this paper we report the fabrication of Ce, Ge and (Ce + Er) doped sol-gel based waveguides on silicon substrates and their optical characterization in terms of light amplification and photosensitivity. We also report results of fabrication and characterization of Bragg gratings in sol-gel based waveguides. The number of layers required for waveguidance and single mode operation has been calculated using the dispersion equations for asymmetric planar waveguides.

Selvarajan, Ananth; Anil Kumar, A.; Anil kumar, D. P.; Hegde, Gopalkrishna M.; Srinivas, Talabuttala

2000-06-01

296

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

NASA Astrophysics Data System (ADS)

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 TiO2/ZnO composite nanostructures through the sol-gel process. Then, by selectively removing the ZnO template, a TiO2 nanotube with contours of the ZnO nanorods is fabricated on the ZnO seed layer coated glass. The resultant TiO2 nanotubes are 1.5 µm long and 100-120 nm in inner diameter, with a wall thickness of ~10 nm. In addition, by adjusting the experimental parameters, such as the dip-coating cycle number or heating rate, porous TiO2 thick films can also be obtained.

Qiu, Jijun; Yu, Weidong; Gao, Xiangdong; Li, Xiaomin

2006-09-01

297

Sol-gel derived ionic copper-doped microstructured optical fiber: a potential selective ultraviolet radiation dosimeter.  

PubMed

We report the fabrication and characterization of a photonic crystal fiber (PCF) having a sol-gel core doped with ionic copper. Optical measurements demonstrate that the ionic copper is preserved in the silica glass all along the preparation steps up to fiber drawing. The photoluminescence results clearly show that such an ionic copper-doped fiber constitutes a potential candidate for UV-C (200-280 nm) radiation dosimetry. Indeed, the Cu?-related visible photoluminescence of the fiber shows a linear response to 244 nm light excitation measured for an irradiation power up to 2.7 mW at least on the Cu-doped PCF core. Moreover, this response was found to be fully reversible within the measurement accuracy of this study ( ± 1%), underlying the remarkable stability of copper in the Cu? oxidation state within the pure silica core prepared by a sol-gel route. This reversibility offers possibilities for the achievement of reusable real-time optical fiber UV-C dosimeters. PMID:23388802

El Hamzaoui, Hicham; Ouerdane, Youcef; Bigot, Laurent; Bouwmans, Géraud; Capoen, Bruno; Boukenter, Aziz; Girard, Sylvain; Bouazaoui, Mohamed

2012-12-31

298

Sol-Gel Synthesis and Densification of Aluminoborosilicate Powders. Part 2: Densification.  

National Technical Information Service (NTIS)

Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions o...

J. Bull G. Selvaduray D. Leiser

1992-01-01

299

Optical pH detector based on LTCC and sol-gel technologies  

NASA Astrophysics Data System (ADS)

This paper presents an investigation on using sol-gel thin film as a material for sensors application in LTCC (Low Temperature Co-fired Ceramics) technology. This material gives the opportunity to make new, low-cost highly integrated optoelectronic devices. Sensors with optical detection are a significant part of these applications. They can be used for quick and safe diagnostics of some parameters. Authors present a pH detector with the optical detection system made of the LTCC material. The main part of the device is a flow channel with the chamber and sol-gel active material. The silica sol-gel with bromocresol green indicator was used. As the absorbance of sol-gel layer changes with the pH value of a measured medium, the transmitted light power was measured. The pH detector was integrated with the electronic components on the LTCC substrate.

Tadaszak, R. J.; ?ukowiak, A.; Golonka, L. J.

2013-01-01

300

Fabrication of Advanced Electrochemical Energy Materials Using Sol-Gel Processing Techniques.  

National Technical Information Service (NTIS)

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 i...

C. T. Chu J. Chu H. Zheng

1995-01-01

301

Sol-gel conversion based on photoswitching between noncovalently and covalently linked netlike supramolecular polymers.  

PubMed

Photo-control over supramolecular sol-gel conversion is achieved by incorporating photoactive coumarin moieties into a tribranched monomer and the self-assembly with ?-CD followed by noncovalent-covalent switchover. PMID:24029875

Zhang, Qiwei; Qu, Da-Hui; Ma, Xiang; Tian, He

2013-10-28

302

Preparation of oxide glasses from metal alkoxides by sol-gel method  

NASA Technical Reports Server (NTRS)

An investigation is carried out on the types of siloxane polymers produced in the course of the hydrolysis of silicon tetraethoxide, as well as the preparation of oxide glasses from metal alkoxides by the sol-gel method.

Kamiya, K.; Yoko, T.; Sakka, S.

1987-01-01

303

Enhanced piezoelectric performance of composite sol-gel thick films evaluated using piezoresponse force microscopy  

PubMed Central

Conventional composite sol-gel method has been modified to enhance the piezoelectric performance of ceramic thick films. Lead zirconate titanate (PZT) and lead magnesium niobate–lead titanate (PMN-PT) thick films were fabricated using the modified sol-gel method for ultrasonic transducer applications. In this work, piezoresponse force microscopy was employed to evaluate the piezoelectric characteristics of PZT and PMN-PT composite sol-gel thick films. The images of the piezoelectric response and the strain-electric field hysteresis loop behavior were measured. The effective piezoelectric coefficient (d33,eff) of the films was determined from the measured loop data. It was found that the effective local piezoelectric coefficient of both PZT and PMN-PT composite films is comparable to that of their bulk ceramics. The promising results suggest that the modified composite sol-gel method is a promising way to prepare the high-quality, crack-free ceramic thick films.

Liu, Yuanming; Lam, Kwok Ho; Kirk Shung, K.; Li, Jiangyu; Zhou, Qifa

2013-01-01

304

Finite element modeling of evaporation and condensation during sol-gel film and fiber formation.  

National Technical Information Service (NTIS)

Free surfaces, multicomponent phase change, volume expansion and compression, and surface tension gradients make for challenging application of the finite element method to sol-gel (ceramic) film and fiber formation. The microstructure of the final produc...

P. R. Schunk A. J. Hurd C. J. Brinker R. R. Rao

1993-01-01

305

Porous alumina scaffold produced by sol-gel combined polymeric sponge method  

NASA Astrophysics Data System (ADS)

Sol gel is a novel method used to produce high purity alumina with nanometric scale. In this study, three-dimensional porous alumina scaffold was produced using sol-gel polymeric sponge method. Briefly, sol gel alumina was prepared by evaporation and polymeric sponge cut to designated sizes were immersed in the sol gel followed by sintering at 1250 and 1550°C. In order to study the cell interaction, the porous alumina scaffold was sterilized using autoclave prior to Human Mesenchymal Stem Cells (HMSCs) seeding on the scaffold and the cell proliferation was assessed by alamarBlue® assay. SEM results showed that during the 21 day period, HMSCs were able to attach on the scaffold surface and the interconnecting pores while maintaining its proliferation. These findings suggested the potential use of the porous alumina produced as a scaffold for implantation procedure.

Hasmaliza, M.; Fazliah, M. N.; Shafinaz, R. J.

2012-09-01

306

Novel Sol-Gel Composite Second Harmonic Generator and Electrooptic Modulator.  

National Technical Information Service (NTIS)

The development of organic inorganic second order nonlinear optical materials is discussed in light of the need to obtain practical (high performance, stable operation, processable and low cost) alternatives to inorganic crystals. Sol gel materials have w...

R. Burzynski M. Casstevens S. Ghosal

1995-01-01

307

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

308

Low Loss Substrates for Microwave Applications and Sol-Gel Processing of Superconductors.  

National Technical Information Service (NTIS)

This document is a final technical report of the research program entitled 'Low Loss Substrates for Microwave Applications and Sol-Gel Processing of Superconductors. Systematic studies on low K oxide substrate materials suitable for epitaxial deposition o...

L. E. Cross R. Roy A. S. Bhalla

1996-01-01

309

Lasing behavior of sol-gel silica doped with UV laser dyes  

NASA Astrophysics Data System (ADS)

Doped and undoped silica samples were fabricated using the sol-gel method. Extended UV transmission down to 200 nm was observed for the undoped sol-gel silica. Three UV dyes (PTP, Exalite 351, and PBD) were used to dope sol-gel silica by diffusion. Lasing and fluorescence properties of these UV laser dyes in the silica matrices were studied. Laser emissions for PTP-, Exalite 351-, and PBD-doped silica samples peaked at 342 nm, 352 nm, and 364 nm. The laser output at 342 nm was the shortest wavelength yet achieved in solid-state dye lasers. The slope efficiency of the PTP-doped sol-gel silica laser was up to 17%. The output energy of the laser emission decreased to 50% of its initial value after 700 shots with a pump repetition rate of 5 Hz.

Lam, K. S.; Lo, D.

1998-04-01

310

Densification of hybrid silica–titania sol–gel films studied by ellipsometry and FTIR  

Microsoft Academic Search

Hybrid silica–titania films were prepared via sol–gel processing, by dip-coating on silicon wafer substrates, from organically-modified silane and titanium isopropoxide precursors. These hybrid sol–gel films were then subjected to selected heat treatments at temperatures up to 950°C and their densification was followed by ellipsometry and infrared absorption (FTIR) spectroscopy. The volume fraction of residual porosity was estimated, based on the

A. Maia Seco; M. Clara Gonçalves; Rui M. Almeida

2000-01-01

311

Acid and Base Catalysts in the Hybrid Silica Sol–Gel Process  

Microsoft Academic Search

Sol–gel silicas were synthesized from the hydrolysis of tetraethoxysilane andN-?-aminoethyl-?-aminopropyltrimethoxysilane in the presence of water and ethanol by using ammonium hydroxide or hydrochloric acid as base or acid catalysts, respectively. The influence of the type of the catalyst employed was studied by comparing the surface areas and pore sizes and volumes for both sol–gel silicas. Nitrogen elemental analysis and13C and29Si

Cesar R. Silva; Claudio Airoldi

1997-01-01

312

Direct laser writing of ridge optical waveguides in silica-titania glass sol-gel films  

Microsoft Academic Search

Sol-gel process is attracting a growing attention as a rather simple technology with potential for low-cost batch manufacture of integrated optical waveguides. Here experimental results are presented on the fabrication of silica-titania sol-gel films and on their laser densification, a technique which may be very useful for rapid circuit prototyping. Transversally multimode waveguides with propagation loss around 1 dB\\/cm have

Stefano Pelli; Giancarlo C. Righini; Antonio Scaglione; Massimo Guglielmi; Alessandro Martucci

1996-01-01

313

Making MgO/SiO2 Glasses By The Sol-Gel Process  

NASA Technical Reports Server (NTRS)

Silicon dioxide glasses containing 15 mole percent magnesium oxide prepared by sol-gel process. Not made by conventional melting because ingredients immiscible liquids. Synthesis of MgO/SiO2 glass starts with mixing of magnesium nitrate hexahydrate with silicon tetraethoxide, both in alcohol. Water added, and transparent gel forms. Subsequent processing converts gel into glass. Besides producing glasses of new composition at lower processing temperatures, sol-gel method leads to improved homogeneity and higher purity.

Bansal, Narottam P.

1989-01-01

314

Amperometric hydrogen peroxide biosensor with silica sol–gel\\/chitosan film as immobilization matrix  

Microsoft Academic Search

A new type of silica sol–gel\\/organic hybrid composite material was developed for the fabrication of an amperometric H2O2 biosensor. This composite consists of sol–gel and the natural polymer chitosan. The composite film was used to immobilize horseradish peroxidase on a carbon paste electrode. The fabrication procedure was systematically optimized to improve the biosensor performance. Hexacyanoferrate(II) was present in the solution

Y Miao; S. N Tan

2001-01-01

315

Sol-gel preparation and properties of alumina adsorbents for gas separation  

Microsoft Academic Search

The sol-gel method is applied to prepare Cu{sup +} or Ag{sup +} containing alumina adsorbents which have potential application in purification or separation of carbon monoxide or olefins containing gases. Wet impregnation and sol-solution mixing methods are used to incorporate the active species into the sol-gel derived γ-alumina support. These alumina adsorbents have the characteristics of large specific surface area,

S. G. Deng; Y. S. Lin

1995-01-01

316

Sol gel based fiber optic sensor for blook pH measurement  

Microsoft Academic Search

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.

S. A. Grant; R. S. Glass

1996-01-01

317

Characterization of sodium fluorescein dye immobilized within sol-gel matrix  

NASA Astrophysics Data System (ADS)

This paper details the absorption and fluorescence spectra of sodium fluorescein in aqueous solution and sol-gel thin films as a function of pH. Our results show that the fluorescence spectrum is dependent not only on the microenvironment surrounding the fluorophore but also the concentration the probe in the sol-gel matrix. The pH sensitive range is also shown to be a function of the emission wavelength.

Holmes-Smith, A. Sheila; Yang, Yatao; Campbell, Michael; Wallace, Peter A.

1996-12-01

318

Electrochromic characterization of Co(OH) 2 thin film prepared by sol–gel process  

Microsoft Academic Search

Electrochemical, spectroscopic and structural measurements were used to characterize the electrochromic behavior and stability of sol–gel deposited Co(OH)2 thin films. These films were prepared from polymeric solutions containing cobalt methoxyethoxide precursor by spin coating technique. The as-deposited films are amorphous and show crystalline structure after heat treatment at 450°C. Sol–gel-deposited cobalt hydroxide films show reversible electrochromic response in 1M LiClO4\\/

Nilgün Özer; Din-Guo Chen; Temel Büyüklimanli

1998-01-01

319

Biocompatibility evaluation of sol–gel coatings for subcutaneously implantable glucose sensors  

Microsoft Academic Search

The objective of the current investigation is to determine the soft-tissue biocompatibility of sol–gel matrices which can be used to optimize the properties of implantable glucose sensors. The biocompatibility of sol–gel matrices with heparin, dextran sulphate, Nafion®, polyethylene glycol, and polystyrene sulphonate was examined in vitro in simulated body fluid and with cell culture experiments using human dermal fibroblasts. Finally,

M. Gerritsen; A. Kros; V. Sprakel; J. A. Lutterman; R. J. M Nolte; J. A. Jansen

2000-01-01

320

Behavoir of Trapped Bromothymol Blue into Sol-Gel Matrix in Presence of CTAB  

Microsoft Academic Search

Encapsulation of bromothymol blue (BTB) into a polysiloxane network was prepared using sol-gel method without using a catalyst. The co-entrappment of the bromothymol blue (BTB) and surfactant cetyltrimethyl ammonium bromide (CTAB) was used to modify the properties of the sol-gel matrixes which may provide a highly porous materials and made the polysiloxane network an excellent host for sensing molecules. Monolithic

Issa M. El Nahhal; Shehata M. Zourab; Fawzi S. Kodeh

2009-01-01

321

Encapsulation of Bromothymol Blue pH?Indicator into a Sol?Gel Matrix  

Microsoft Academic Search

Transparent monolithic silica doping with bromothymol blue has been prepared by the acid catalyzed sol?gel reaction of tetraethylorthosilicate in the presence of bromothymol blue. The immobilized bromothymol blue shows behavior similar to its solution counterpart. It retains its structure during the sol?gel reactions in terms of response to pH. Polarized light microscopy has indicated that the bromothymol blue molecules are

Farid R. Zaggout

2006-01-01

322

Tantalum-tungsten oxide thermite composites prepared by sol-gel synthesis and spark plasma sintering  

Microsoft Academic Search

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and\\/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide

Joshua D. Kuntz; Alexander E. Gash; Octavio G. Cervantes; Zuhair A. Munir

2010-01-01

323

Tantalum–tungsten oxide thermite composites prepared by sol–gel synthesis and spark plasma sintering  

Microsoft Academic Search

Energetic composite powders consisting of sol–gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and\\/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol–gel derived nanostructured tungsten oxide

Joshua D. Kuntz; Octavio G. Cervantes; Alexander E. Gash; Zuhair A. Munir

2010-01-01

324

Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering  

Microsoft Academic Search

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and\\/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten

O Cervantes; J Kuntz; A Gash; Z Munir

2009-01-01

325

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

326

Physical properties and structure of organic-inorganic hybrid materials produced by sol-gel process  

Microsoft Academic Search

Two approaches of the sol-gel process to prepare organic-inorganic hybrids are reviewed. One method is simple and involves mixing an organic polymer with a metal alkoxide such as tetraethoxysilane (TEOS). During the sol-gel process the inorganic mineral is deposited in the organic polymer matrix forming hydrogen bonding between organic phase and inorganic phase. In the small angle X-ray scattering (SAXS)

Shoichiro Yano; Keisuke Iwata; Kimio Kurita

1998-01-01

327

Restricted diffusion and release of aroma molecules from sol-gel-made porous silica particles  

Microsoft Academic Search

The aim of the current study is to predict the release kinetics of organic molecules entrapped in sol-gel-made silica particles using both pulsed field gradient-nuclear magnetic resonance (PFG-NMR) techniques and model calculations to describe restricted diffusion. The macroscopic release profile of aroma molecules from sol-gel-made particles is measured directly by UV-VIS spectroscopy, while the release kinetics are calculated by the

Susanne R. Veith; Eric Hughes; Sotiris E. Pratsinis

2004-01-01

328

Water-based synthesis and characterization of sol-gel hydroxyapatite ceramics  

Microsoft Academic Search

Sol-gel technology for hydroxyapatite (HAp) synthesis has been developed more than a decade ago. The existing sol-gel HAp synthetic methods which used alkoxide-based precursors require solvent-based diluting media, a moisture-controlled atmosphere, prolonged synthesis time generally greater than 24 hours, and a heat treatment at temperature >500°C over a time period of several hours. Those factors limit practical applications of HAp,

Dean-Mo Liu

2004-01-01

329

Characterization of ZnO Thin Film Deposited by Sol-Gel Process  

Microsoft Academic Search

ZnO is a wide band gap semiconductor which is used as transparent electrode in solar cells, chemical and gas sensors and light emitting diode etc. This paper reports the sol gel preparation and characterization of ZnO thin film. ZnO thin film was prepared by sol-gel process using zinc acetate dehydrate as a precursor, 2-methoxy ethanol as a solvent and monoethanolamine

Vijay Kumar Anand; S. C. Sood; Anurekha Sharma

2010-01-01

330

Conformal sol-gel coatings on three-dimensional nanostructured templates  

Microsoft Academic Search

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

Michael R. Weatherspoon

2008-01-01

331

Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors  

Microsoft Academic Search

ZnO thin films were fabricated by a sol-gel method using Zn(CH3COO)2·2H2O as starting material in order to prepare an acetone gas sensor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. The sol-gel solution is coated on alumina substrates with various thicknesses by spin coating technique and heat treated to

Nitul Kakati; Seung Hyun Jee; Su Hyun Kim; Jun Young Oh; Young Soo Yoon

2010-01-01

332

Fiber optic oxygen sensors based on the sol-gel coating technique  

Microsoft Academic Search

Two fiber optic oxygen sensor designs were demonstrated by sol-gel coatings doped with an organo-metallic complex, ruthenium (II) tris-4,7-diphenyl-1,10-phenanthroline. The first design implemented a porous optical fiber coated with sol-gel that showed high sensitivity (less than 1 ppm) towards oxygen gas and a dynamic range up to 1% oxygen. The second optical sensor was based on a collimator device which

Michael Krihak; Michael T. Murtagh; Mahmoud R. Shahriari

1996-01-01

333

Synthesis via sol–gel process and characterization of novel organic–inorganic coatings  

Microsoft Academic Search

Organic–inorganic coatings were synthesized from tetraethoxysilane (TEOS) and vinyltriacetoxysilane (VTAS) via dual process involving sol–gel reaction and radical polymerization. The deposition of the films was carried out using the spin-coating technique with the sample holder spinning at 1500rpm. In order to determine the nature of products formed during the sol–gel reaction (i.e. polymerization) and to study the kinetics of this

Ouissem Trabelsi; Lan Tighzert; Omar Jbara; Aomar Hadjadj

2011-01-01

334

Rare-Earth Doping of Silica Based Optical Fiber by the Sol-Gel Method  

Microsoft Academic Search

Using a sol-gel process for rare earth doping, a minimum background loss of less than 2 dB\\/km at 1.1 mum has been achieved in erbium doped Al:SiO_2 single-mode fibers. The long lifetime for fluorescence of 520 mu sec for neodymium in an Al:SiO_2 glass host prepared by the sol-gel method suggested that this approach provides a very uniform doping of

Fengqing Wu

1995-01-01

335

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

336

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

Microsoft Academic Search

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

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

2000-01-01

337

The properties of antimony-doped tin oxide thin films from the sol-gel process  

Microsoft Academic Search

Antimony-doped tin oxide thin films have a range of technical applications as conductive coatings, and sol-gel processing seems to offer a number of advantages over other coating techniques. In this study, the sol was prepared from stannic chloride and antimony chloride in alcohol. Films were achieved either from spin-coating of colloidal gel suspensions or from spray-coating of suspensions of sol-gel-derived

Yung-Jen Lin; Ching-Jiunn Wu

1997-01-01

338

Properties of sol-gel PZT films based on indium-tin oxide substrate  

Microsoft Academic Search

Sol-gel ferroelectric thin films of PZT [Pb(Zr0.52Ti0.48)O3] were prepared by spin coating on indium-tin oxide (ITO) substrate formed by chemical vapor deposition (CVD). The properties of PZT film after rapid thermal annealing (RTA) were tested by X-ray diffraction (XRD) for orientation of crystallization, and by ferroelectric tester RT66A for electrical characteristics. The results show that sol-gel PZT can be crystallized

Jinhua Li; Ningyi Yuan; Kun Li; Kwok Ying Tong; Helen Lai-Wa Chan

2001-01-01

339

Synthesis of Indium Tin Oxide Thin Films by Cvd and Sol-Gel Processing  

Microsoft Academic Search

The object of this work was to synthesize indium tin oxide thin films on glass substrates using Chemical Vapor Deposition and Sol-gel processes. Starting materials included indium-2,2,6,6-tetramethylheptane - 3,5-dione and tin chloride as precursors for the CVD method, indium nitrates (In(NO_3)_35H _2O), tin chloride and ethylene glycol for the sol-gel method. A spin coating system was used to prepare the

Laurent-Sebastien Bernard

1994-01-01

340

Structural and Optical Properties of Sol-Gel Deposited Proton Conducting Ta 2 O 5 Films  

Microsoft Academic Search

Proton conducting tantalum oxide films were deposited on ITO (Indium Tin Oxide) coated glass, fused silica and soda-lime glass substrates by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC2H5)5 as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400°C, were amorphous. Films heat treated at higher temperatures were

Nilgun Ozer; Carl M. Lampert

1997-01-01

341

Effectiveness of sol-gel treatments coupled with copper and boron against subterranean termites  

Microsoft Academic Search

Wood modification by sol-gel treatments shows many positive features, like antimicrobial properties. Wood was also successfully modified with alkoxysilanes enhancing its resistance against soil micro-organisms. Silver, copper, zinc compounds, boric acid or organic biocides such as alkylammonium compounds may be added to the sol-gel to enhance its biocidal properties. Nevertheless, if some of these active ingredients and compounds are not

E. Feci; L. Nunes; S. Palanti; S. Duarte; G. Predieri; F. Vignali

342

Structural evolution during calcination of sol-gel synthesized alumina and alumina-8 vol% zirconia composite  

Microsoft Academic Search

Alumina and alumina-8 vol% zirconia (3 mol% yttria) composite powders were synthesized via a sol-gel process using metal chlorides\\u000a as precursors. Sol-gel synthesized alumina and alumina-zirconia composite powders were initially amorphous and contained structural\\u000a water. Calcination was necessary to drive off the water and prompt crystallization of the powder. Calcination of synthesized\\u000a powder was performed at various temperatures from 400–1300°C.

J. KUO; D. L BOURELL

1997-01-01

343

Luminescent properties of trivalent ytterbium ions in sol-gel produced alumina  

Microsoft Academic Search

Solution growth of materials now offers a viable alternative to traditional high temperature melt growth processes. The sol-gel method, one such solution technique, chemically produces inorganic materials from aqueous solutions. The sol-gel process can be used to produce alumina, Al2O3 , in a variety of forms from porous, transparent monoliths to ceramics. Aluminum oxide, a large bandgap material (9 eV),

John Kenneth Krebs

2000-01-01

344

Novel hybrid sol–gel coatings for corrosion protection of AZ31B magnesium alloy  

Microsoft Academic Search

This work aims to develop and study new anticorrosion films for AZ31B magnesium alloy based on the sol–gel coating approach.Hybrid organic–inorganic sols were synthesized by copolymerization of epoxy-siloxane and titanium or zirconium alkoxides. Tris(trimethylsilyl) phosphate was also used as additive to confer additional corrosion protection to magnesium-based alloy. A sol–gel coating, about 5-?m thick, shows good adhesion to the metal

S. V. Lamaka; M. F. Montemor; A. F. Galio; M. L. Zheludkevich; C. Trindade; L. F. Dick; M. G. S. Ferreira

2008-01-01

345

Sol-gel processing of controlled pore films  

SciTech Connect

During sol-gel film formation via dipping, polymeric precursors are aggregated on the substrate surface by a process involving gravitational flow, drying, and continued condensation reactions. To understand film formation in situ, we use ellipsometric imaging and infrared spectroscopy. The structure and porosity of the deposited film are determined by SAXS, ellipsometry, and surface acoustic wave (SAW) methods. We find that weakly-branched silicate precursors deposited near the isoelectric point of silica result in dense films (volume percent porosity, V/sub p/ < 5%) in which any pores present have radii <0.2 nm, regardless of precursor size. More compact precursors result in films in which the porosity and refractive index are controlled by the size of the precursor species prior to deposition and the relative rates of condensation and evaporation during deposition. The porosity and refractive index of these films may be varied as follows: volume percent porosity (0 less than or equal to V/sub p/ less than or equal to 56%); pore radius (0 less than or equal to r less than or equal to 3.1 nm); surface area (1.2 less than or equal to S less than or equal to 263 m/sup 2//g); refractive index (1.18 less than or equal to n less than or equal to 1.45). For repulsive, monosized particulate precursors, higher coating rates promote ordering providing an additional means of pore size control. 18 refs., 7 figs.

Brinker, C.J.; Frye, G.C.; Hurd, A.J.; Ward, K.J.; Ashley, C.S.

1989-01-01

346

Preparation of quantum dots by the sol-gel process  

NASA Astrophysics Data System (ADS)

The preparation of semiconductor dots with high number density and narrow particle size distribution, which are essential for high nonlinearity susceptibility, has been studied on CdS dispersed soda-borosilicate glasses by the sol-gel process using tetramethoxysilane (TMOS), triethylborate (B(OEt)3), sodium acetate (NaOAc) and cadmium acetate (Cd(OAc)2) as the starting materials. Both number density and particle size distribution of the CdS crystallites were dependent upon the treatment conditions in the conversion of Cd(OAc)2 to CdO and CdO to CdS inside the porous gel. The optimum heat-treatment temperature for the conversion of Cd(OAc)2 to CdO was around 400 degree(s)C, and that for the conversion of CdO and CdS by exposing the gel to H2S was around 120 degree(s)C. Glass containing about 10 wt% CdS crystallites 4 - 7 nm in diameter was obtained by sintering the gel at 590 degree(s)C under the above treatment conditions.

Yamane, Masayuki; Takada, Toshimi; Mackenzie, John D.; Li, Chia-Yen

1992-12-01

347

Sol gel growth of titania from electrospun polyacrylonitrile nanofibres  

NASA Astrophysics Data System (ADS)

In this paper we report on the development of TiO2 surface-residing electrospun nanofibres with controllable density of TiO2 on the support fibre surface by means of an electrospinning technique and a sol-gel process. The TiO2 precursor/PAN composite nanofibres were synthesized by electrospinning a polyacrylonitrile (PAN) solution containing TiO2 precursors. Subsequently, an immersion of the electrospun composite nanofibres in deionized water led to the hydrolysis of the TiO2 precursors. SEM, TEM and XRD pattern analyses demonstrated that TiO2 was formed and resided on the nanofibre surface. On further calcining the hydrolysed nanofibres in air at 300 °C, TiO2 could be conveniently converted into anatase without essentially changing the morphology of the hydrolysed nanofibres. Furthermore, surface photovoltage spectroscopy (SPS) confirmed that the TiO2 surface-residing nanofibre nonwovens had a strong SPS response. It can be attributed that the surface residence of TiO2 permits the transfer of the photogenerated electron originating from TiO2 to ITO electrodes. Potential applications of the TiO2 surface-residing nanofibres include filters, catalysis films and environmental pollution remediation films.

Hong, Youliang; Li, Domgmei; Zheng, Jian; Zou, Guangtian

2006-04-01

348

Tuning of sol-gel derived PZT MEMS resonators  

NASA Astrophysics Data System (ADS)

This paper demonstrates the tunability of resonant frequencies for MEMS piezoelectric resonators acting in the d33 mode by experiment and theoretical analysis. Thin-film MEMS beams made by sol-gel PZT processing are first fabricated and tested to investigate the tuning capability. The three-layered interdigitated-electrode trapezoidal beams are then modeled by finite element analysis for validation. Beam curl and undercutting are also examined to present an alternative way of finding the stress gradient in comparison to Stoney's formula. The experimental and analytical results indicate that piezoelectric MEMS resonators have the ability to passively tune their resonant frequencies between open-circuit and short-circuit frequencies. Tuning of 0.2-0.6% is demonstrated experimentally, which compares with finite element predictions of 1.02-1.08%. Consideration is given to the reason for the differences in experimental percentages versus those predicted numerically, including the use of bulk PZT values in the ANSYS simulations, the undercut and curling effects of fabrication, and the low percentage of piezoelectric poling in the length direction.

Knight, Ryan R.; Frederick, Amanda A.; Mo, Changki; Clark, William W.

2010-12-01

349

Nanocrystalline diamond films fabricated by sol gel technique  

NASA Astrophysics Data System (ADS)

This study describes nanocrystalline diamond coating using sol-gel technique as an easy coating technique for nanocrystalline diamond films. To make a nanodiamond sol for coating, diamond nanoparticles (<10 nm) synthesized by a detonation method are put into distilled water and are dispersed by an ultrasonic wave, and then are mechanically milled with zirconia balls. The viscosity of the prepared nanodiamond sol increases with the content of the added diamond nanoparticles. The prepared nanodiamond sol is spin-coated at 3000 rpm on a quartz substrate. TEM observation shows that the obtained film consisting of the deposited diamond nanoparticles is approximately 500 nm in thickness. The obtained films are heated at <873 K in air atmosphere. The results of the XRD and Raman analysis indicate that all the fabricated nanocrystalline diamond films have the diamond (sp 3) and amorphous carbon (sp 2) structures. The indentation measurements are made for the nanocrystalline diamond films fabricated, and the indentation hardness of the film heated at 573 K indicates the maximum value of 367 MPa. This technique can fabricate nanocrystalline diamond films easily at a much lower processing temperature than the processing temperature of conventional diamond coating.

Hanada, K.; Matsuzaki, K.; Sano, T.

2007-09-01

350

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

351

Preparation and characterization of conductive and transparent ruthenium dioxide sol-gel films.  

PubMed

RuO2 conductive thin films were synthesized using the sol-gel method and deposited onto transparent insulating substrates. The optical transmission, film thickness, surface morphology and composition, resistivity, and spectroelectrochemical performance have been characterized. The optical transmission values of these films ranged from 70 to 89% in the visible region and from 56 to 88% in the infrared region. Resistivity values of the RuO2 sol-gel films varied from 1.02 × 10(-3) to 1.13 ? cm and are highly dependent on the initial solution concentration of RuO2 in the sol-gel. The RuO2 sol-gel films were used as electrodes for the electrochemical oxidation and reduction of ferrocenemethanol. The electrochemical behavior of our novel RuO2 sol-gel films was compared to that of a standard platinum disk electrode and showed no appreciable differences in the half-wave potential (E1/2). The mechanical and chemical stability of the coatings was tested by physical abrasion and exposure to highly acidic, oxidizing Piranha solution. Repeated exposure to these extreme conditions did not result in any appreciable decline in electrochemical performance. Finally, the use of the novel RuO2 sol-gel conductive and transparent films was demonstrated in a spectroelectrochemistry experiment in which the oxidation and reduction of ferrocenemethanol was monitored via UV-vis spectroscopy as the applied potential was cycled. PMID:24221640

Allhusen, John S; Conboy, John C

2013-11-27

352

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

353

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

354

Entrapment of subtilisin in ceramic sol-gel coating for antifouling applications.  

PubMed

Enzymes with antifouling properties are of great interest in developing nontoxic antifouling coatings. A bottleneck in developing enzyme-based antifouling coatings is to immobilize the enzyme in a suitable coating matrix without compromising its activity and stability. Entrapment of enzymes in ceramics using the sol-gel method is known to have several advantages over other immobilization methods. The sol-gel method can be used to make robust coatings, and the aim of this study was to explore if sol-gel technology can be used to develop robust coatings harboring active enzymes for antifouling applications. We successfully entrapped a protease, subtilisin (Savinase, Novozymes), in a ceramic coating using a sol-gel method. The sol-gel formulation, when coated on a stainless steel surface, adhered strongly and cured at room temperature in less than 8 h. The resultant coating was smoother and less hydrophobic than stainless steel. Changes in the coating's surface structure, thickness and chemistry indicate that the coating undergoes gradual erosion in aqueous medium, which results in release of subtilisin. Subtilisin activity in the coating increased initially, and then gradually decreased. After 9 months, 13% of the initial enzyme activity remained. Compared to stainless steel, the sol-gel-coated surfaces with active subtilisin were able to reduce bacterial attachment of both Gram positive and Gram negative bacteria by 2 orders of magnitude. Together, our results demonstrate that the sol-gel method is a promising coating technology for entrapping active enzymes, presenting an interesting avenue for enzyme-based antifouling solutions. PMID:23020255

Regina, Viduthalai Rasheedkhan; Søhoel, Helmer; Lokanathan, Arcot Raghupathi; Bischoff, Claus; Kingshott, Peter; Revsbech, Niels Peter; Meyer, Rikke Louise

2012-11-01

355

Silica sol–gel composite film as an encapsulation matrix for the construction of an amperometric tyrosinase-based biosensor  

Microsoft Academic Search

An amperometric tyrosinase enzyme electrode for the determination of phenols was developed by a simple and effective immobilization method using sol–gel techniques. A grafting copolymer was introduced into sol–gel solution and the composition of the resultant organic–inorganic composite material was optimized, the tyrosinase retained its activity in the sol-gel thin film and its response to several phenol compounds was determined

B Wang; J Zhang; S Dong

2000-01-01

356

Particle size effect on porous Sol–Gel doped cladding U-shaped optical fiber critical micelle concentration (CMC) sensor  

Microsoft Academic Search

In this paper, a sol–gel derived coating U-shaped optical fiber sensors for measurement of critical micelle concentration of surfactants has been studied. The doped sol–gel cladding fiber was used to construct an active cladding U-shaped optical fiber CMC measurement sensor. The porous sol–gel film was deposited a 1000 ?m core plastic clad silica fiber after removing the cladding of the fiber

C. D. Singh; M. Ogita

2004-01-01

357

An optical fiber biosensor for chlorpyrifos using a single sol–gel film containing acetylcholinesterase and bromothymol blue  

Microsoft Academic Search

An optical fiber biosensor consisting of acetylcholinesterase (AChE) and bromothymol blue (BTB) doped sol–gel film was employed to detect organophosphate pesticide chlorpyrifos. The main advantage of this optical biosensor is the use of a single sol–gel film with immobilized AChE and BTB. The compatibility of this mixture (AChE and BTB) with the sol–gel matrix has prevented leaching of the film.

Bambang Kuswandi; Chulaifah Indah Fikriyah; Agus Abdul Gani

2008-01-01

358

A study of chemical parameters of the internal gelation based sol-gel process for uranium dioxide  

NASA Astrophysics Data System (ADS)

Internal gelation process is one of the important sol-gel routes for the preparation of spherical particles of fuel materials. Successful preparation of defect free fuel particles has been reported only with a narrow range of feed solution compositions. Investigations have been carried out to study the gelation behaviour of solutions containing uranyl nitrate, hexamethylene-tetramine (hexa) and urea with a view to defining the regions of possible interest to the process. A gelation field diagram has been constructed defining regions where a single phase gel can be readily obtained. A number of compositions from this gelation field diagram have been used for the preparation of UO 2 microspheres and it was observed that good spherical particles could be obtained with uranium concentrations ranging from 0.7 to 1.5 molar. The mole ratio (hexa, urea)/uranium for obtaining good particles decreased with increasing uranium concentration.

Vaidya, V. N.; Mukherjee, S. K.; Joshi, J. K.; Kamat, R. V.; Sood, D. D.

1987-05-01

359

Recycling of chemicals from alkaline waste generated during preparation of UO 3 microspheres by sol-gel process  

NASA Astrophysics Data System (ADS)

Internal gelation process, one of the sol-gel processes for nuclear fuel fabrication, offers many advantages over conventional powder pellet route. However, one of the limitation of the process is generation of large volume of alkaline liquid waste containing hexamethylenetetramine, urea, ammonium nitrate, ammonium hydroxide etc. Presence of ammonium nitrate with hexamethylenetetramine and urea presents a fire hazard which prevents direct disposal of the waste as well as its recycle by evaporation. The paper describes the studies carried out to suitably process the waste. Nitrate was removed from the waste by passing through Dowex 1 × 4 anion exchange resin in OH - form. 1.0 M NaOH was used to regenerate the resin. The nitrate-free waste was further treated to recover and recycle hexamethylenetetramine, urea and ammonium hydroxide for preparation of UO 3 microspheres. The quality of the microspheres obtained was satisfactory. An optimized flow sheet for processing of the waste solution has been suggested.

Kumar, Ashok; Vittal Rao, T. V.; Mukerjee, S. K.; Vaidya, V. N.

2006-05-01

360

Adsorption of Wells–Dawson tungsten heteropolyacid on sol–gel alumina: Structural features and thermal stability  

Microsoft Academic Search

The Wells–Dawson tungsten heteropolyacid, H6P2W18O62 supported on sol–gel and non-sol–gel alumina has been investigated by infrared spectroscopy (IR), thermal analysis (TGA\\/DSC), and X-ray diffraction (XRD). X-ray diffraction indicates that the heteropolyacid primary structure in bulk form holds up to 350?°C and by supporting it on the sol–gel alumina the thermal stability rose to 650?°C. UV–vis spectroscopy showed that the sol–gel

A. Tarlani; M. Abedini; M. Khabaz; M. Mohammadpour Amini

2005-01-01

361

NonAqueous Battery Systems  

Microsoft Academic Search

Lithium and sodium are light and highly electronegative elements which form the basis of anodes for high-energy-density battery systems. Their high chemical reactivity requires the use of ionic conductors based on non-aqueous solvents, polymers, solid electrolytes or fused salts. An associated range of cathode materials enables cells to be fabricated with open-circuit voltages from 1.5 to 4.0 V. Practical non-aqueous

Colin A. Vincent

1996-01-01

362

Vibrational spectroscopic studies of triethoxy(4-(trifluoromethyl)-phenyl) silane and its sol-gel coating.  

PubMed

We have prepared a silica sol-gel using triethoxy (4-(trifluoromethyl)-phenyl) silane (TETFMPS) as a precursor in ethanol solution under acidic condition. The prepared sol-gel was applied to the surface treatment of aluminum for corrosion prevention. Infrared and Raman spectra of the silane coupling agent, sol-gel and sol-gel films on metal have been collected. Infrared spectroscopy has been used to study the thermal effect on the chemical composition of xerogel. Results suggested that TETFMPS molecule has a C(s) point group symmetry with the plane of reflection orthogonal to the phenyl ring and the organic part of the sol-gel film remains essentially unchanged at or below 450 °C but decomposes at or above 550 °C. After the decomposition of the organic branch, the remaining film is composed of silica. Vibrational assignments were suggested by using the collected spectroscopic data in different states along with the group vibrational frequencies and other related references. PMID:22925916

Li, Ying-Sing

2012-10-01

363

Affinity of antifluorescein antibodies encapsulated within a transparent sol-gel glass  

SciTech Connect

Low temperature processed, porous sol-gel glasses represent a new class of materials for immobilization of biomolecules. The ability to form these materials into films, monoliths, and fibers to produce high-purity, porous glasses and the fact that they are optically transparent and chemically inert make them an intriguing platform for the development of chemical biosensors. In this paper, we report on the first attempt to encapsulate an intact antibody in a sol-gel glass matrix. Specifically, we present results on the affinity of sol-gel-encapsulated polyclonal antifluorescein. The results demonstrate that the sol-gel-encapsulated antibody retains an affinity for fluorescein; the affinity constant (K[sub f]) for antibody-hapten complex is on the order of 10[sup 7] M[sup [minus]1]. The encapsulation process decreases K[sub f] by about 2 orders of magnitude compared to the native system in buffer solution. The effect of aging and drying on the K[sub f] for sol-gel-encapsulated antifluorescein is reported. Finally, we demonstrate that the intact antibody affinity can be maintained using simple storage protocols. 31 refs., 8 figs.

Wang, R.; Narang, U.; Prasad, P.N.; Bright, F.V. (State Univ. of New York, Buffalo, NY (United States))

1993-10-01

364

Synthesis, stability, and sulfation properties of sol-gel-derived regenerative sorbents for flue gas desulfurization  

SciTech Connect

The sol-gel method is applied to prepare {gamma}-alumina-supported copper oxide and calcium oxide sorbents containing 10--50 wt% active species. The prepared sorbents are characterized for their pore texture, dispersion of active species on the surface of support, and desulfurization properties. The sol-gel-derived alumina-supported sorbents have a relatively large surface area (> 200 m{sup 2}/g) and pore volume (> 0.3 cm{sup 3}/g) and uniform pore size distribution (20--60 {angstrom}). Thermal and chemical stability of the sol-gel-derived sorbents is studied by comparing the pore texture data of the sorbents before and after several different heat treatments. The stability results show that the pore structure of the sol-gel-derived sorbents is stable in the normal conditions of the flue gas desulfurization process. It is found that CuO/{gamma}-Al{sub 2}O{sub 3} sorbent containing 20 wt% of CuO coated as a monolayer or submonolayer on the surface of support has the highest SO{sub 2} sorption capacity (22.5 wt% at 500 C). The sol-gel-derived CuO/{gamma}-Al{sub 2}O{sub 3} sorbent exhibits desired sulfation and regeneration properties.

Deng, S.G.; Lin, Y.S. [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering] [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering

1996-04-01

365

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

366

Sol-gel-based molecularly imprinted xerogel for capillary microextraction.  

PubMed

A novel molecularly imprinted xerogel (MIX) based on organically modified silica (ORMOSIL) was successfully prepared for on-line capillary microextraction (CME) coupled with high-performance liquid chromatography (HPLC). The sol-gel-based xerogel was prepared using only one precursor and exhibited extensive selectivity towards triazines along with significant thermal and chemical stability. Atrazine was selected as a model template molecule and 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) as a precursor in which the propylmethacrylate moiety was responsible for van der Waals, dipole-dipole, and hydrogen-bond interactions with the template. This moiety plays a key role in creation of selective sites while methoxysilyl groups in TMSPMA acted as crosslinkers between the template and the propylmethacrylate moiety. Moreover, a non-imprinted xerogel (NIX) was also prepared in the absence of the template for evaluating the extraction efficiency of the prepared MIX. Then, the prepared imprinted and non-imprinted xerogels were used for extraction of three selected analytes of triazines class including atrazine, ametryn, and terbutryn, which have rather similar structures. The extraction efficiency of the prepared xerogel for atrazine, the template molecule, was found to be ten times greater than the efficiency achieved by the non-imprinted one. In the meantime, the extraction efficiency ratio of MIX to NIX for ametryn and terbutryn was also rather significant (eight times). Moreover, other compounds from different classes including dicamba, mecoprop, and estriol were also analyzed to evaluate the selectivity of the prepared MIX towards triazines. The ratio of enrichment factors (EF) of MIX to NIX for atrazine, ametryn, terbutryn, dicamba, mecoprop, and estriol were about 10, 8, 8, 2, 2, and 3, respectively. The linearity for the analytes was in the range of 5-700 ?g L(-1). Limit of detection was in the range of 1-5 ?g L(-1) and the RSD% values (n = 5) were all below 6.6% at the 20 ?g L(-1) level. The developed method was also applied to real water samples and the relative recovery percentages obtained for the spiked water samples were from 92 to 104%. The CME loop, containing the prepared MIX, exhibited a rather long life time due to its remarkable solvent and mechanical stability. Even after 100 runs, no decrease in the peak areas was observed. The developed method could easily provide the possibility of preparing a selective sorbent in a unique way with the lowest possible cost and time. PMID:22752449

Bagheri, Habib; Piri-Moghadam, Hamed

2012-09-01

367

Friedel–Crafts catalysis using supported reagents. Synthesis, characterization and catalytic application of ZnCl 2 supported on fluoride?modified sol–gel?derived aluminosilicates  

Microsoft Academic Search

ZnCl2–aluminosilicate catalysts were prepared via a sol–gel route involving fluoride?catalyzed hydrolysis of aluminum and silicon\\u000a alkoxides in the presence of NaF, KF, NH4F and ZnF2. The catalysts were characterized by employing 29Si, 27Al and 19F solid?state MAS NMR. The dependence of the activities of the catalysts on the nature and amount of fluoride present in the\\u000a catalysts were investigated using

Jack M. Miller; Mary Goodchild; Jhansi L. Lakshmi; David Wails; J. Stephen Hartman

1999-01-01

368

Surfactant-Assisted Sol-Gel Auto-Combustion Synthesis of SR-HEXAFERRITE Nanopowder Using Different Fuels and Basic Agents  

NASA Astrophysics Data System (ADS)

In this research Sr-hexaferrite powder was synthesized by a sol-gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C13H30BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800 °C respectively, in the presence of citric acid, trimethylamine and surfactant.

Ghobeiti Hassab, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

369

Surfactant-Assisted Sol-Gel Auto-Combustion Synthesis of Sr-Hexaferrite Nano-Crystalline Powder Using Different Fuels and Basic Agents  

NASA Astrophysics Data System (ADS)

In this research Sr-hexaferrite powder was synthesized by a sol-gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C13H30BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800° C respectively, in the presence of citric acid, trimethylamine and surfactant.

Ebrahimi, S. A. S.; Hasab, M. G.; Badiei, A.

2010-03-01

370

Laser-assisted sol-gel growth and characteristics of ZnO thin films  

SciTech Connect

ZnO thin films were grown on Si(100) substrates by a sol-gel method assisted by laser beam irradiation with a 325 nm He-Cd laser. In contrast to conventional sol-gel ZnO thin films, the surface morphology of the laser-assisted sol-gel thin films was much smoother, and the residual stress in the films was relaxed by laser irradiation. The luminescent properties of the films were also enhanced by laser irradiation, especially, by irradiation during the deposition and post-heat treatment stages. The incident laser beam is thought to play several roles, such as annihilating defects by accelerating crystallization during heat treatment, enhancing the surface migration of atoms and molecules, and relaxing the ZnO matrix structure during crystallization.

Kim, Min Su; Kim, Soaram [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae 621-749 (Korea, Republic of); Leem, Jae-Young [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae 621-749 (Korea, Republic of); Department of Nano Engineering, Inje University, Gimhae 621-749 (Korea, Republic of)

2012-06-18

371

Sol-gel derived 45S5 bioglass: synthesis, microstructural evolution and thermal behaviour.  

PubMed

In this work, the 45S5 bioactive glass was synthesized through an aqueous sol-gel method. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy, the thermal behaviour was investigated by thermogravimetric and differential thermal analysis, crystallization kinetics and phase evolution were followed by X-ray diffraction measurements. The sintering behaviour of the sol-gel derived 45S5 was then studied by dilatometry and the microstructural evolution was followed step-by-step, interrupting the thermal cycle at different temperatures. In vitro dissolution tests were performed in order to assess the degradation behaviour of sol-gel derived 45S5 samples thermally treated at different temperatures. A relevant influence of the calcination conditions (namely, dwelling time and temperature) of the as-prepared powder on the phase appearance and its sintering behaviour as well as on the porosity features, in terms of pore dimension and interconnectivity, of the fired materials was stated. PMID:22580755

Cacciotti, Ilaria; Lombardi, Mariangela; Bianco, Alessandra; Ravaglioli, Antonio; Montanaro, Laura

2012-08-01

372

Optical pH sensor based on sol-gel-doped new luminescent dye  

NASA Astrophysics Data System (ADS)

The sol-gel process is an exciting new technology that enables the production of gel glasses and ceramic materials at room temperature. Sol-gel technology offers simple methods for manipulation of the structure, configuration, composition and chemical characteristics of organic matrices. A novel longwave luminescent dye based on the europium luminescence initiated by a covalently bonded antenna fluorophore was designed, synthesized and characterized. The dye was successfully entrapped into various sol-gel and ormosil matrices and consequent optical- , leaching- and light fastness-properties were tested. Finally, sensor layer based on TMOS doped with Eu3+- complex and bromothymol blue was found to be most appropriate for purposes of sensing pH over the range 5-10.

Lobnik, Aleksandra; Niederreiter, Karlheinz; Uray, Georg

1999-11-01

373

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

374

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

375

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

376

Correlation between sol-gel reactivity and wettability of silica films deposited on stainless steel  

NASA Astrophysics Data System (ADS)

Sol-gel silica films were deposited on 316L and 409 stainless steel substrates in order to investigate their wettability properties. These films were deposited by dip-coating varying some parameters of the sol-gel process, including the acid used in the synthesis, its concentration, and the heat treatment temperature. Water and oil contact angles were measured on the surfaces and discussed regarding the physico-chemical and morphological properties of the prepared films. The findings shown in this work allow correlating the wettability behavior of silica coatings with the sol-gel reactivity of sols prepared using various amounts of nitric acid. It was observed that the more reactive the silica sol, the more hydrophilic and oleophilic the prepared coating. The presence in the films of alkoxy residues due to an incomplete condensation reaction could decrease both the polar and dispersive components of the coating surface energy, respectively responsible for water and oil wetting.

Houmard, M.; Nunes, E. H. M.; Vasconcelos, D. C. L.; Berthomé, G.; Joud, J.-C.; Langlet, M.; Vasconcelos, W. L.

2014-01-01

377

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

378

Nonlinear optical properties of CdTe included in sol-gel by a new technique  

NASA Astrophysics Data System (ADS)

Sol-gel derived silica glasses are well suited as host for molecular dopants that show specific optical properties, such as laser action (high second and third order nonlinear coefficients). Such materials are of interest in optical waveguide and switching for telecommunication networks. The material is prepared by sol-gel technique in which some nanocrystallites of semiconductor (II-VI) are included, specially CdTe. Nanocrystallites are prepared out of the host matrix and included in the sol-gel after. The nanoparticles are prepared by sono-electrochemical technique. Sono-electrochemistry, or pulsed electrodeposition in presence of high intensity ultrasound, is used to product powders. The nanoparticles are characterized by scanning and transmission microscopy, electron diffraction, and x-ray fluorescence. The nonlinear refractive index and absorption are measured by the Z-scan method at 532 nm (Nd-YAG pulsed laser).

Loicq, J.; Torrenti, C.; Renotte, Yvon L.; Calberg, C.; Delplancke, J. L.; Lion, Yves F.

2000-05-01

379

Sol-gel preparation and properties of alumina adsorbents for gas separation  

SciTech Connect

The sol-gel method is applied to prepare Cu{sup +} or Ag{sup +} containing alumina adsorbents which have potential application in purification or separation of carbon monoxide or olefins containing gases. Wet impregnation and sol-solution mixing methods are used to incorporate the active species into the sol-gel derived {gamma}-alumina support. These alumina adsorbents have the characteristics of large specific surface area, high dispersion of active species on the grain surface, and mesopore size with a uniform pore size distribution. The gas chromatographic technique determines the carbon monoxide adsorption properties on these alumina adsorbents. Adsorption equilibrium constants, adsorption rate constants, axial dispersion coefficients, heat of adsorption, and adsorption activation energy are determined from GC response peaks by using the moment method. The alumina adsorbents prepared by the sol-gel method appear to be superior to the similar adsorbents prepared by other methods.

Deng, S.G.; Lin, Y.S. [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering] [Univ. of Cincinnati, OH (United States). Dept. of Chemical Engineering

1995-03-01

380

Calcium phosphate formation within sol-gel prepared titania in vitro and in vivo.  

PubMed

Calcium phosphate formation is induced within sol-gel prepared titania and grows toward a calcium phosphate solution in which the titania is immersed. The implantation of this sol-gel prepared titania film coating on TiA16V4 core into the femurs of goats shows an accumulation of calcium phosphate within the titania film 12 weeks postoperatively, which leads to the connection of the titania film coating to the bone. Therefore, sol-gel prepared titania is probably bioactive. The results indicate that hydrated titania gel is able to generate calcium phosphate by intake of calcium and phosphate from the surrounding solution. Sufficient TiOH concentration at the titania surface is needed to start this process. Titanium could be bioactive, if its hydrolysis can be accelerated. PMID:8113236

Li, P; de Groot, K

1993-12-01

381

UV-nanoimprinting lithography of Bragg Gratings on hybrid sol-gel based channel waveguides  

NASA Astrophysics Data System (ADS)

We report on the fabrication in a single step of a channel grating loaded waveguide on Titanium based hybrid sol-gel material. This result has been accomplished by the merging of several lithographic techniques, namely conventional, laser interference, and soft lithography. Conventional lithographic processes have been employed for fabricating channel waveguides on a previously holographically written planar photopolymerizable sol-gel film. Such structures have been used as a master to produce a negative replica in polydimethylsiloxane (PDMS) and subsequently exploited to reproduce the master patterns by UV-nanoimprinting on photopolymerizable hybrid sol-gel coatings (titanium and 3-(trimethoxysilyl)propyl methacrylate). Optical and morphological characterization of the various fabrication steps and of the final device have been reported and discussed.

Prosposito, P.; Casalboni, M.; Orsini, E.; Palazzesi, C.; Stella, F.

2010-11-01

382

Highly efficient solid-state neutron scintillators based on hybrid sol-gel nanocomposite materials  

NASA Astrophysics Data System (ADS)

This research highlights opportunities in the formulation of neutron scintillators that not only have high scintillation efficiencies but also can be readily cast into two-dimensional detectors. Series of transparent, crack-free monoliths were prepared from hybrid polystyrene-silica nanocomposites in the presence of arene-containing alkoxide precursor through room temperature sol-gel processing. The monoliths also contain lithium-6 salicylate as a target material for neutron-capture reactions and amphiphilic scintillator solution as a fluorescent sensitizer. Polystyrene was functionalized by trimethoxysilyl group in order to enable the covalent incorporation of aromatic functional groups into the inorganic sol-gel matrices for minimizing macroscopic phase segregation and facilitating lithium-6 doping in the sol-gel samples. Neutron and alpha responses of these hybrid polystyrene-silica monoliths were explored.

Kesanli, Banu; Hong, Kunlun; Meyer, Kent; Im, Hee-Jung; Dai, Sheng

2006-11-01

383

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

384

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

385

Development and characterization of molecularly imprinted sol-gel materials for the selective detection of DDT.  

PubMed

Molecularly imprinting sol-gel materials for DDT using both a noncovalent and a covalent approach was examined. A nonpolar porous sol-gel network was created through the use of the bridged polysilsesquioxane, bis-(trimethoxysilylethyl)benzene (BTEB), as the principal sol-gel component. Noncovalent molecular imprinting was deemed unsuccessful, presumably because of the lack of strong intermolecular interactions that can be established between the DDT and the sol-gel precursor. A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of two 3-isocyanatopropyltriethoxysilanes with one of two different template molecules: 4,4'-ethylenedianiline (EDA) or 4,4'-ethylidenebisphenol (EBP). After formation of the sol-gel, the bonds linking the spacer template to the matrix were cleaved in a manner that generated a pocket of the appropriate size bordered by amine groups that could aid in the binding of DDT through weak hydrogen bonding interactions. Experiments indicated that DDT could be bound selectively by such an approch. To generate a sensor, an environmentally sensitive fluorescent probe, 7-nitrobenz-2-oxa-1,3-diazole, (NBD) located adjacent to the DDT binding site was used to transduce the binding of analyte. EDA-imprinted sol-gels, deposited as films on glass microscope slides, were shown to quantitatively detect DDT in water to a limit-of-detection of 50 ppt with a response time of <60 s. Repeat measurements could be made with the same sensing films after rinsing with acetone between each measurement. The EDA sensing material was selective for DDT and other structurally similar molecules. However, the sensing film design was limited by the relatively minor changes in fluorescence intensity upon binding DDT. This situation may be remedied by an alternative methodology that can facilitate attachment of the NBD fluorophore in an optimal position proximal to the binding pocket. PMID:11811423

Graham, Amy L; Carlson, Catherine A; Edmiston, Paul L

2002-01-15

386

Development of novel Sol-Gel Indicators (SGI's) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator  

SciTech Connect

The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

Livingston, R.R.; Baylor, L.; Wicks, G.G.

1992-11-03

387

Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups  

NASA Technical Reports Server (NTRS)

Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

Stiegman, Albert E.

1995-01-01

388

Novel sol-gel-based Pt nanocluster catalysts for propane dehydrogenation  

SciTech Connect

The authors report the 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 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 these catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.

Sault, A.G.; Martino, A.; Kawola, J.S.; Boespflug, E.

2000-04-25

389

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

390

Comparative study of ?-nickel molybdate phase obtained by conventional precipitation and the sol-gel method  

Microsoft Academic Search

Various samples of ?-NiMoO4 phase consisting of nickel and molybdenum in a stoichiometric ratio were prepared by precipitation from nickel nitrate hexahydrate and ammonium heptamolybdate, and also in presence of Si(OCH3)4 and Si(OEt)3(CH2)3NH(CH2)NH2 using the sol-gel method.The stabilised ?-NiMoO4 phase is synthesised using the sol-gel technique. The development of this phase is achieved by using a direct crystallisation in the

A. Kaddouri; E. Tempesti; C. Mazzocchia

2004-01-01

391

Zinc oxide films prepared by sol–gel spin coating technique  

Microsoft Academic Search

Zinc oxide (ZnO) thin films and micro- and nanostructures are very promising candidates for novel applications in emerging\\u000a thin-film transistors, solar cells, sensors and optoelectronic devices. In this paper, a low-cost sol–gel spin coating technique\\u000a was used to fabricate ZnO films on glass substrates. The sol–gel fabrication process of the ZnO films is described. The influence\\u000a of precursor concentration on

Sharul Ashikin Kamaruddin; Kah-Yoong Chan; Ho-Kwang Yow; Mohd Zainizan Sahdan; Hashim Saim; Dietmar Knipp

2011-01-01

392

Synthesis of superhydrophobic alumina membrane: Effects of sol-gel coating, steam impingement and water treatment  

NASA Astrophysics Data System (ADS)

Ceramic membranes possess natural hydrophilicity thus tending to absorb water droplets. The absorption of water molecules on membrane surface reduces their application in filtration, membrane distillation, osmotic evaporation and membrane gas absorption. Fluoroalkylsilane (FAS) grafting allows the conversion of hydrophilic ceramic membranes into superhydrophobic thin layer, but it usually introduces a great increment of mass transfer resistance. In this study, superhydrophobic alumina membranes were synthesized by dip coating alumina support into sol-gel and grafted with the fluoroalkylsilane (FAS) named (heptadecafluoro-1,1,2,2-tetra hydrodecyl) triethoxysilane. Steam impingement and water treatment acted as additional steps to generate surface roughness on sol-gel and most importantly to reduce mass transfer resistance. Superhydrophobic alumina membrane with high water contact angle (158.4°) and low resistance (139.5 ± 24.9 G m-1) was successfully formed when the alumina membrane was dip coated into sol-gel for 7 s, treated with steam impingement for 1 min and immersed in hot water at 100 °C. However, the mass transfer resistance was greatly induced to 535.6 ± 23.5 G m-1 when the dip coating time was increased to 60 s. Long dip coating time contributes more on the blockage of porous structure rather than creates a thin film on the top of membrane surface. Reducing the pore size and porosity significantly due to increase of coating molecules deposited on the membrane. Steam impingement for 1 min promoted the formation of cones and valleys on the sol-gel, but the macro-roughness was destroyed when the steam impingement duration was extended to more than 3 min. The immersions of membranes into hot water at temperatures higher than 60 °C encouraged the formation of boehmite which enhances the formation of additional roughness and enlarges pore size greatly. Thus, this work showed that the formation of superhydrophobic alumina membrane with low resistance is influenced by three factors; sol-gel dip coating time, steam impingement time and temperature of water treatment. The optimum dip coating time could promote appropriate thickness of the sol-gel layer on the membrane support. The highest surface roughness and porosity could be created when the sol-gel layer was further treated with optimum steam impingement duration and immersed in hot water at 100 °C. The presence of appropriate sol-gel thickness can reduce the penetration of FAS during the grafting and reduce the membrane resistance.

Ahmad, N. A.; Leo, C. P.; Ahmad, A. L.

2013-11-01

393

Preparation and flammability properties of hybrid materials containing phosphorous compounds via sol-gel process  

Microsoft Academic Search

Organic-inorganic hybrid coatings containing phosphoric acid (PA) bonded to the organic-inorganic network were prepared from\\u000a tetraethoxysilane (TEOS) using a sol-gel process. The effect of sol-gel phosphate-based flame retardant coating on polyacrylonitrile\\u000a fabric properties (flammability, stiffness, and strength) was investigated. Sample characterization of the coated samples\\u000a were investigated using differential thermal\\/thermogravimetric analysis (DTA\\/TGA), Fourier transform infrared spectroscopy\\u000a (FTIR), X-ray diffractometer (XRD),

Necla Yaman

2009-01-01

394

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.

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

2010-01-01

395

Structural and optical properties of sol-gel deposited proton conducting Ta 2 O 5 films  

Microsoft Academic Search

Proton conducting tantalum oxide films were deposited on ITO (Indium Tin Oxide) coated glass, fused silica and soda-lime glass\\u000a substrates by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC2H5)5 as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400°C, were\\u000a amorphous. Films heat treated at higher temperatures were

Nilgun Ozer; Carl M. Lampert

1997-01-01

396

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

397

Preparation of bimetallic Pt-Sn/alumina catalysts by the sol-gel method  

SciTech Connect

A series of bimetallic Pt-Sn/alumina catalysts were prepared by the sol-gel method. The structure of these catalysts was studied by physical adsorption of nitrogen. Reactions between n-hexane and hydrogen were carried out in order to study the catalytic activity and deactivation trends. This work shows that the sol-gel method offers an interesting and potentially useful method of preparing supported metallic and bimetallic samples. In this study we deal only with xerogel samples. 18 refs., 2 figs., 4 tabs.

Balakrishnan, K.; Gonzalez, R.D. (Tulane Univ., New Orleans, LA (United States))

1994-07-01

398

Capacitance spectroscopy of alumina sol–gel capacitors with Al top contacts  

Microsoft Academic Search

We measured the complex capacitance C(f) of ITO\\/sol–gel alumina\\/Al capacitors deposited on glass (and some on stainless steel foil) in the frequency range 15 Hz–10 MHz.\\u000a The sol–gel films were deposited by dip-coating and following a two-step process. The capacitance C(f) found was much higher than that of a pure Al2O3-film due to the remaining porosity of the film and the uptake

Patrick De Visschere; Karel Vanbesien

2008-01-01

399

Aluminum lactate – An attractive precursor for sol–gel synthesis of alumina-based glasses  

Microsoft Academic Search

A novel aluminum precursor, aluminum lactate (Al(lact)3), was used in the sol–gel synthesis of alumina-based systems. The peculiar chelation properties of aluminum lactate in aqueous solution make this precursor quite attractive for the sol–gel synthesis of alumina-containing materials. Based on the reaction of aluminum lactate with different precursors such as phosphorus, boron, fluorine and others, (Na2O–)Al2O3–P2O5, (Na2O–)Al2O3–B2O3, (Na2O–)Al2O3–B2O3–P2O5, (Na–)Al–P–O–F, amorphous

Long Zhang; Carla C. de Araujo; Hellmut Eckert

2007-01-01

400

Oxide ceramic fibers by the sol-gel methods. Final report, December 1986-February 1988  

SciTech Connect

Sol-gel processing has many advantages over traditional powder based ceramic processing. These advantages include better homogeniety, higher purity and low-temperature synthesis. Additionally, the sol-gel process is the only low temperature process available to make high-temperature stable oxide fibers. Most of these fibers cannot be formed by drawing via the traditional melt method. This report includes research conducted on the preparation of lanthanum chromite fibers. Lanthanum chromite's high-temperature stability was enhanced by coating with alumina. Additionally, at test high temperatures, several commercial fibers, including alumina fibers were tested with this rig.

Mackenzie, J.D.; Ono, K.

1989-02-10

401

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

402

Fabrication of rare-earth doped sol-gel based composite planar optical waveguides on glass  

NASA Astrophysics Data System (ADS)

Incorporation of active materials, such as Neodymium (Nd3+) and Erbium (Er3+) in suitable host media has potential applications in lasers and amplifiers. We have fabricated composite planar waveguides on glass substrates doped with Nd3+ and Er3+ ions using the sol-gel process. The composite sol-gel was prepared using polyvinylpyrrolidone as the organic part, while Tetraethyl orthosilicate and Titanium isopropoxide formed the inorganic part. The samples were prism coupled and it was found that they supported single mode at (lambda) equals 633 nm. Gain measurement of the Nd3+ samples have also been carried out.

Natarajan, S. R.; Srinivas, Talabuttala; Joseph, M. J.; Selvarajan, Ananth

1998-12-01

403

Sol-gel composite hydrothermal processing of barium strontium titanate films for microwave frequency applications  

Microsoft Academic Search

Stoichiometric barium strontium titanate (BST) films of composition Ba 0.7Sr0.3TiO3 with thickness >2mum have been fabricated on various substrates including Si\\/SiO2\\/Pt and Al 2O3\\/Au by hydrothermal sol-gel composite processing. This film deposition technique involves the treatment of a spun-on sol-gel composite film in an alkaline aqueous solution at temperatures from 50-200°C and pressures of 1-15 atm. An initial hydrolysis procedure

Kim Zelonka

2005-01-01

404

Fundamental electrochemiluminescence characteristics of fluorine-doped tin oxides synthesized by sol-gel combustion.  

PubMed

Fluorine-doped tin oxide (FTO) materials synthesized by sol-gel combustion method were investigated for electrochemical luminescence (ECL) application. Effects of sol-gel combustion conditions on the structures and morphology of the porous FTO (p-FTO) materials were studied. ECL efficiency of p-FTO-based cell was about 251 cd/m2 at 4 V bias, which is higher than the sell using only FTO electrodes (102.8 cd/m2). The highest intensity of the emitting light was obtained at the wavelength of about 610 nm. The porous FTO layer was effective for increasing ECL intensities. PMID:24245225

Moon, B H; Chaoumead, A; Sung, Y M

2013-10-01

405

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

406

Effect of plasma pretreatment on adhesion and mechanical properties of sol-gel nanocomposite coatings on polycarbonate  

Microsoft Academic Search

Adhesion of the coatings to the substrate plays a vital role in improving mechanical properties of sol-gel coatings especially when deposited on plastics. In the present study, an attempt was made to study the effect of atmospheric air plasma surface activation on the adhesion of sol-gel nanocomposite coatings on polycarbonate substrate. The sol was synthesized by the hydrolysis and condensation

K. R. C. Soma Raju; L. Sowntharya; S. Lavanya; R. Subasri

2012-01-01

407

Studies of (3-mercaptopropyl)trimethoxylsilane and bis(trimethoxysilyl)ethane sol-gel coating on copper and aluminum  

NASA Astrophysics Data System (ADS)

Bis(trimethoxysilyl)ethane (BTMSE) and (3-mercaptopropyl)trimethoxysilane (MPTMS) have been used as precursors to prepare sol-gels and hybrid sol-gel under acidic condition. From the X-ray photoelectron spectroscopy data on MPTMS sol-gel coated aluminum and copper, it has been shown that the silane film is covalently bonded to Al surface through the interfacial condensation. There is no evidence of bonding interaction between the thiol group and the Cu. The recorded reflection adsorption IR (RAIR) spectrum has provided evidence that the coating BTMSE film covalently interacts with Al. Vibrational assignments have been suggested for pure BTMSE, BTMSE sol-gel, BTMSE xerogel, and BTMSE coated Al panel based on the group frequencies and the variation of frequencies with the sample treatment conditions. The progression of condensation reaction has been observed from the IR spectra of the BTMSE sol-gel and the sol-gel coated film after the treatments at different temperatures with different lengths of time. The corrosion protection of the sol-gel coated Al and Cu has been characterized in NaCl solutions by cyclic voltammetric, potentiodynamic polarization and impedance spectroscopy methods. All these electrochemical measurements indicate that the sol-gel coated metals have better corrosion protection than the corresponding uncoated metals.

Li, Ying-Sing; Lu, Weijie; Wang, Yu; Tran, Tuan

2009-09-01

408

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

409

Environmentally benign sol-gel antifouling and foul-releasing coatings.  

PubMed

Biofouling on ships and boats, characterized by aquatic bacteria and small organisms attaching to the hull, is an important global issue, since over 80000 tons of antifouling paint is used annually. This biofilm, which can form in as little as 48 hours depending on water temperature, increases drag on watercraft, which greatly reduces their fuel efficiency. In addition, biofouling can lead to microbially induced corrosion (MIC) due to H2S formed by the bacteria, especially sulfate-reducing bacteria. When the International Maritime Organization (IMO) international convention banned the use of effective but environmentally damaging coatings containing tributyl tin in 2008, the development of clean and effective antifouling systems became more important than ever. New nonbiocidal coatings are now in high demand. Scientists have developed new polymers, materials, and biocides, including new elastomeric coatings that they have obtained by improving the original silicone (polydimethylsiloxane) formulation patented in 1975. However, the high cost of silicones, especially of fluoropolymer-modified silicones, has generally prevented their large-scale diffusion. In 2009, traditional antifouling coatings using cuprous oxide formulated in copolymer paints still represented 95% of the global market volume of anti-fouling paints. The sol-gel nanochemistry approach to functional materials has emerged as an attractive candidate for creating low fouling surfaces due to the unique structure and properties of silica-based coatings and of hybrid inorganic-organic silicas in particular. Sol-gel formulations easily bind to all types of surfaces, such as steel, fiberglass, aluminum, and wood. In addition, they can cure at room temperature and form thin glassy coatings that are markedly different from thick silicone elastomeric foul-releasing coatings. Good to excellent performance against biofouling, low cure temperatures, enhanced and prolonged chemical and physical stability, ease of application, and the waterborne nature of sol-gel coatings all support the diffusion of these paints to efficiently reduce the accumulation of fouling layers on valued surfaces immersed in marine or fluvial waters. Furthermore, sol-gel glassy coatings are transparent and can be effectively applied to optical devices, windows, and solar panels used in lake, fluvial, or marine environments. Sol-gel technology is eminently versatile, and the first generation sol-gel paints have already shown good performance. Even so, vast opportunities still exist for chemists to develop novel sol-gel derived coatings to both prevent biofouling and enhance the hydrodynamic properties of boat and ship hulls. Moreover, researchers have prepared and applied multifunctional sol-gel coatings providing protection against both biofouling and corrosion. They have tested these in the marine environment with good preliminary results. In this Account, we discuss some of our new strategies for the controlled functionalization of surfaces for the development of efficient antifouling and foul-releasing systems and summarize the main achievements with biocidal and nonbiocidal sol-gel coatings. We conclude by giving insight into the marine coatings and sol-gel products markets, providing arguments to justify our conclusion that the sol-gel coatings technology is now a mature platform for the development of economically viable and environmentally friendly antifouling and foul-release formulations of enhanced performance. PMID:24397288

Detty, Michael R; Ciriminna, Rosaria; Bright, Frank V; Pagliaro, Mario

2014-02-18

410

Selectivity differences between sol-gel coated and immobilized liquid film open-tubular columns for gas chromatography.  

PubMed

The solvation parameter model is used to determine the system constants for two sol-gel coated open-tubular columns at five equally spaced temperatures in the range 60-140 degrees C. Differences in the system constants as a function of temperature are used to determine the affect of sol-gel structure on the selectivity of SolGel-l and SolGel-Wax columns compared with conventionally coated and immobilized poly(dimethylsiloxane) and poly(ethylene glycol) stationary phases. The sol-gel columns should be suitable for similar separations to those presently performed on conventional immobilized liquid film columns of the same type but selectivity differences for polar compounds, which depend on temperature, should be anticipated. PMID:12537368

Kiridena, Waruna; Poole, Colin F; Koziol, Wiadyslaw W

2002-12-01

411

Capillary electrochromatography using continuous-bed columns of sol–gel bonded silica particles with mixed-mode octadecyl and propylsulfonic acid functional groups  

Microsoft Academic Search

Continuous-bed columns containing sol–gel bonded 3 ?m silica particles with mixed-mode octadecyl and propylsulfonic acid functional groups (ODS\\/SCX) were prepared by first packing the ODS\\/SCX particles into a fused-silica capillary, then filling the packed capillary with a siliceous sol–gel, curing the sol–gel, and finally drying the column with supercritical carbon dioxide. The performance of the sol–gel bonded ODS\\/SCX columns was

Qinglin Tang; Milton L Lee

2000-01-01

412

Renewable silica sol–gel derived carbon composite based glucose biosensor  

Microsoft Academic Search

An amperometric mediated glucose biosensor has been developed based on a sol–gel derived carbon composite material. Glucose oxidase and the mediator vinylferrocene have been immobilised within the porous, rigid and organically modified silicate network in the composite material. The organic group in the silicate network controls the hydrophobicity of the electrode surface and thus limits the wettability of the electrode

J. Li; L. S. Chia; N. K. Goh; S. N. Tan

1999-01-01

413

Chromatographic characterization of macroporous monolithic silica prepared via sol-gel process  

Microsoft Academic Search

A continuous porous silica monolith prepared by the sol-gel process including phase separation was aged in a basic solvent making use of hydrolysis of urea to prepare extended mesopore structures for chromatographic applications. The dissolution–reprecipitation kinetics at the interfaces between wet gel skeletons and an external solvent affected the size and volume of pores formed within the skeletons. At above

Norio Ishizuka; Hiroyoshi Minakuchi; Kazuki Nakanishi; Kazuyuki Hirao; Nobuo Tanaka

2001-01-01

414

Preparation and characterization of cerium doped silica sol–gel coatings on glass and aluminum substrates  

Microsoft Academic Search

Chromates are among the most common substances used as corrosion inhibitors. However, these compounds are highly toxic, and an intense effort is being undertaken to replace them. Cerium compounds seem to fulfil the basic requirements for consideration as alternative corrosion inhibitors. The aim of this work was to study the effect of the incorporation of cerium ions in silica sol–gel

A. Pepe; M. Aparicio; S. Ceré; A. Durán

2004-01-01

415

A Novel Preparation Method for Foamed Silica Ceramics by Sol-Gel Reaction and Mechanical Foaming  

Microsoft Academic Search

A simple method for obtaining silica foam has been developed by combining sol-gel reaction and mechanical foaming without added organic pore formers, in order to reduce generation of CO2 and harmful gases by decomposition of the organic compounds. The silica foam was prepared by mechanically foaming the silica sol and controlling the viscosity change and gelling. The gelation time of

Takahiro Tomita; Shinji Kawasaki; Kiyoshi Okada

2004-01-01

416

Optical fibre sensors sensitized by phenyl-modified porous silica prepared by sol–gel  

Microsoft Academic Search

Porous silica and phenyl-modified porous silica were prepared by sol–gel method as cladding for optical fibres and tested for the chemical detection of aromatic and alkane vapours. The refractive indices and optical attenuation of the layers have been determined from the measured angular distributions of the output optical power. For this purpose, a model based on geometrical optics has been

F Abdelmalek; J. M Chovelon; M Lacroix; N Jaffrezic-Renault; V Matejec

1999-01-01

417

Glass Coating for PDMS Microfluidic Channels by Sol-Gel Methods  

Microsoft Academic Search

Soft lithography in polydimethylsiloxane (PDMS) allows one to fabricate complex microfluidic devices easily and at low cost. However, PDMS swells in the presence of many organic solvents, which can significantly degrade the performance of PDMS microfluidic devices. We present a method to coat PDMS channels with a glass-like layer using sol-gel chemistry. As a demonstration of chemical resistance, we flow

Thao Do; Adam Abate; David Weitz; Christian Holtze

2008-01-01

418

Rare Earth based Sol-Gel Materials: An Intra- and Inter Collegiate Collaborative Research Project  

Microsoft Academic Search

Sol-gel glasses containing rare earth (RE) impurities form an exciting class of new optical materials with potential uses as phosphors and solid state laser media. The low temperature glass synthesis based on the liquid organic precursor tetramethoxysilane allows incorporation of higher RE concentrations than in traditional melt glasses without compromising the amorphous character of the material. The synthesis and spectroscopic

Ann Silversmith

2004-01-01

419

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, Yuan-Hsiang; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

1999-02-01

420

Cathode materials for lithium ion batteries prepared by sol-gel methods  

Microsoft Academic Search

Improving the preparation technology and electrochemical performance of cathode materials for lithium ion batteries is a current major focus of research and development in the areas of materials, power sources and chemistry. Sol-gel methods are promising candidates to prepare cathode materials owing to their evident advantages over traditional methods. In this paper, the latest progress on the preparation of cathode

H. Liu; Y. P. Wu; E. Rahm; R. Holze; H. Q. Wu

2004-01-01

421

Electrode materials for lithium secondary batteries prepared by sol–gel methods  

Microsoft Academic Search

Since the commercialization of lithium secondary batteries in the early of 1990s, their development has been rapid. Nowadays, improving the preparation technology and electrochemical performance of their electrode materials is a major focus in research and development of the materials, power sources and chemistry. Sol–gel methods are a promising way to prepare electrode materials due to their evident advantages over

L. J. Fu; H. Liu; C. Li; Y. P. Wu; E. Rahm; R. Holze; H. Q. Wu

2005-01-01

422

Sol–gel synthesis, microstructure and adsorption properties of hollow silica spheres  

Microsoft Academic Search

Spherical colloidal particles with a hollow interior and a mesoporous shell are particularly useful for drug delivery and release because such spheres combine the unique properties of hollow interior (for storing the drug) with mesoporous shell (for controlled release). Hollow silica spheres (HSS) with a mesoporous shell were prepared via a sol–gel process in the presence of dual templates polystyrene

Haitao Fan; Zhibin Lei; Jia Hong Pan; X. S. Zhao

2011-01-01

423

Sol-gel Transition of Methylcellulose Solution in the Coexistence of Hexadecyltrimethylammonium Bromide and Sodium Chloride  

NASA Astrophysics Data System (ADS)

The sol-gel transition of methylcellulose (MC) solution in the presence of NaCl and hexadecyltrimethylammonium bromide (HTAB), together with MC/NaCl solution in the presence of HTAB and MC/HATB solution in the presence of NaCl, was investigated by the rheological measurements. It has been found that the sol-gel transition temperature of MC solution decreases linearly with the concentration of NaCl in solution but increases linearly with the concentration of HTAB in solution, respectively. However, the sol-gel transition temperature of MC/NaCl solution in the presence of HTAB keeps the same value, independent of the concentration of HTAB in solution. On the other hand, the sol-gel transition temperature of MC/HTAB solution decreases linearly with the concentration of NaCl in solution. The experimental results suggest that, for MC/NaCl solution in the presence of HTAB, the salt-induced spherical micelles of HTAB should have formed in bulk solution. For MC solution in the absence of NaCl, no spherical micelles have been formed in bulk solution, though the concentration of HTAB in our experiment is almost one order of magnitude higher than the critical micelle concentration of HTAB in polymer-free solution. In fact, due to adsorption of HTAB on MC chains, the realconcentration of HTAB in bulk solution, is much less than the apparent concentration of HTAB dissolved in MC solution.

Zhou, Shan; Yang, Hai-yang; Xie, Yong-jun; Li, Hua-zhen; Liu, Guang-ming

2011-08-01

424

Sol-gel technology applied to crystalline ceramic nuclear waste forms  

Microsoft Academic Search

The sol-gel process is being developed for the solidification and isolation of high-level nuclear fuel waste. Three gelation methods are being developed for producing alternative waste forms. These include internal gelation for producing spheres of up to 1 mm diam suitable for coating, external gelation, and water extraction methods for producing material suitable for alternate ceramic processing. In this study

P. Angelini; W. D. Bond; A. J. Caputo; J. E. Mack; W. J. Lackey; D. A. Lee; D. P. Stinton

1980-01-01

425

Sol-Gel Protective Coatings for Black Chrome Solar Selective Films.  

National Technical Information Service (NTIS)

Electrodeposited black chrome solar selective films degrade rapidly when heated to temperatures above 300 exp 0 C in air. The application of sol-gel protective coatings to the black chrome films has been investigated as a possible means to improve the oxi...

C. J. Brinker R. B. Pettit

1981-01-01

426

Coatings produced by electrophoretic deposition from nano-particulate silica sol–gel suspensions  

Microsoft Academic Search

Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 ?m. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of

Y. Castro; B. Ferrari; R. Moreno; A. Durán

2004-01-01

427

Synthesis of Nano Silica Particles for Polishing Prepared by Sol–Gel Method  

Microsoft Academic Search

In order to produce an excellent abrasive, a fabrication method for cocoon shaped silica particles has been studied. The particles are prepared from TMOS, water, ammonia and methanol by a sol–gel method. The method is to add the methanol solution of TMOS at a constant supply rate to a mixture of water, ammonia and methanol. Effects of various reaction conditions

Yasuhiko Arai; Hiroyo Segawa; Kazuaki Yoshida

2004-01-01

428

Preparation and properties of KNbO 3 via the sol-gel method  

Microsoft Academic Search

Sol-gel processing of a solution of niobium and potassium ethoxides in methanol was used to prepare polycrystalline potassium niobate ceramic discs. Gel powders completely crystallized after only 2 h at 600 ° C. Crystallized powders were hot-pressed at pressures less than half of that required in conventional methods. Densities of up to 99% were achieved without encountering the common problem

Azar Nazeri-Eshghi; A. X. Kuang; J. D. Mackenzie

1990-01-01

429

Preparation of CdS-Doped Glasses by the Sol-Gel Method.  

National Technical Information Service (NTIS)

CdS-doped SiO2 glasses have been prepared through the sol-gel process. A methanol solution of cadmium nitrate and thiourea in a molar ratio of 1:2 was added to the SiO2 sol prepared from silicon tetraethoxide. The mixed solution was left for gelation at 5...

N. Tohge M. Asuka T. Minami

1992-01-01

430

Process Dependent Electrical Characteristics and Equivalent Circuit Model of SOL-GEL Based PZT Capacitors.  

National Technical Information Service (NTIS)

Studies of electrical properties and an equivalent circuit model is developed for ferroelectric PZT(Ti = 60%) thin film capacitors made by sol-gel spin coating with Pt electrodes. The equivalent circuit consists of two major parts: serial space charge cap...

T. Mihara H. Watanabe H. Yoshimori C. A. Paz De Araujo

1991-01-01

431

Surface Skin Development and Rupture During Sol-Gel Spin-Coating  

Microsoft Academic Search

Spin coating is one of the standard methods for depositing sol-gel, nanocomposite, or polymer coatings onto flat substrates (silicon wafers, glass plates for displays, sensor substrates, etc.). Our recent research has been focused at understanding a wide variety of defect formation mechanisms and looking for ways to prevent these defects. A key aspect of spin-coating is the solvent evaporation that

Dunbar P. Birnie; III

2004-01-01

432

Lead Zirconate Titanate Nanowire Growth Via Spin Coating in Conjunction with Sol-Gel Process  

Microsoft Academic Search

Lead zirconate titanate (PZT) nanowires are successfully synthesized by a spin coating of sol-gel solution on a highly ordered porous alumina membrane (PAM). Field emission scanning electron microscope images show that PZT nanowires are well packed inside the nanochannels of the PAM. A selected area electron diffraction pattern reveals that they are polycrystalline. They exhibit a high aspect-ratio (up to

Jongok Kim; Yong Chan Choi; Ki-Seog Chang; Sang Don Bu

2007-01-01

433

Smart electrochemical sensor for some neurotransmitters using imprinted sol–gel films  

Microsoft Academic Search

A hybrid sol–gel material formed by acid hydrolysis of a mixture of tetraethylorthosilicate (TEOS) and phenyltriethylorthosilicate (PTEOS) as functional monomers was imprinted by tyramine and dopamine as template molecules for the purpose of molecular recognition. Imprinted materials were spin coated as thin films on the surface of glassy carbon electrodes and then were characterized using cyclic voltammetry (CV). After extraction

Nada F. Atta; Ali M. Abdel-Mageed

2009-01-01

434

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

435

BaTiO3 thin films fabricated by sol-gel process  

NASA Astrophysics Data System (ADS)

Typical characteristics of BaTiO3 thin films, such as hysterisis behavior, spontaneous polarization below the Curie temperature, faster switching speed etc., are particularly of much attention for high capacitance integrated elements, dynamic random access memories (DRAMs), phase conjugation, holographic optical data storage, two-beam coupling and optical computing. Several techniques have been employed for the fabrication process of such ferroelectric thin films. Among other methods, Sol-Gel and MOD prove to be a powerful and inexpensive means to deposit thin films. The main advantages of these deposition techniques are good homogeneity, ability to precisely control the stoichiometry of the film, lower temperature processing, and the ability to produce high-purity materials for electronics and optics without much investment in equipment. We report the structural characterization of BaTiO3 films deposited on single crystal Si (100) and MgO (100) substrates by sol-gel process. The films were prepared by the sol-gel process and annealed at different temperatures. In this method the sol-gel polymerization is initiated by adding water to a solution of alkoxide in methanol. The chemical conditions are generally chosen in such a way that nearly complete hydrolysis occurs. A series of experiments ranging from X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), were conducted on the spin-coated films and their correspondingly annealed films at different temperatures.

Hernandez Cruz, Daniel; Lessard, Roger A.

2002-10-01

436

Influence of crystallization kinetics on texture of sol–gel PZT and BST thin films  

Microsoft Academic Search

The evolution of morphology of sol–gel PZT and BST thin films during rapid thermal annealing (RTA) is investigated by recording of elastic light scattering data in reflected mode. The analysis of film morphology and texture evolution obtained by XRD reveals the dependence of crystallization kinetics on the annealing conditions. The evolution of film morphology during the transition to the perovskite

V. Ya Shur; E. B Blankova; A. L Subbotin; E. A Borisova; D. V Pelegov; S Hoffmann; D Bolten; R Gerhardt; R Waser

1999-01-01

437

Influence of Crystallization Kinetics on Texture of Sol-Gel PZT and BST Thin Films  

Microsoft Academic Search

The evolution of morphology of sol-gel PZT and BST thin films during rapid thermal annealing (RTA) is investigated by recording of elastic light scattering data in reflected mode. The analysis of film morphology and texture evolution obtained by XRD reveals the dependence of crystallization kinetics on the annealing conditions. The evolution of film morphology during the transition to the per-

E. B. Blankova; A. L. Subbotin; E. A. Borisov; D. V. Pelegov; D. Bolten; R. Waser

1999-01-01

438

Inverse magnetocaloric effect in sol-gel derived nanosized cobalt ferrite  

Microsoft Academic Search

The magnetocaloric properties of cobalt ferrite nanoparticles were investigated to evaluate the potential of these materials as magnetic refrigerants. Nanosized cobalt ferrites were synthesized by the method of sol-gel combustion. The nanoparticles were found to be spherical with an average crystallite size of 14 nm. The magnetic entropy change (Delta S m) calculated indirectly from magnetization isotherms in the temperature

E. Veena Gopalan; I. A. Al-Omari; D. Sakthi Kumar; Yasuhiko Yoshida; P. A. Joy; M. R. Anantharaman

2010-01-01

439

Influence of the alkyl-substituted silane precursor on sol–gel encapsulated lipase activity  

Microsoft Academic Search

Lipase from Candida rugosa was encapsulated within a chemically inert sol–gel support prepared by polycondensation of three precursor types (tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS) and polydimethylsilane (PDMS)) in the presence and absence of polyethylene glycol (PEG) and polyvinyl alcohol (PVA) as additives. Silica and their derivatives were characterised with regard to mean pore diameter, specific surface area, pore size distribution (BET

Cleide M. F Soares; Onélia A dos Santos; José E Olivo; Heizir F de Castro; Flavio F de Moraes; Gisella M Zanin

2004-01-01

440

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

441

Recubrimientos sol-gel obtenidos por deposición electroforética (EPd) sobre metales  

Microsoft Academic Search

El proceso sol-gel es un método de gran interés para la producción de películas vítreas sobre metales, que actúan como barrera protectora frente a la oxidación y aumentan su resistencia a la corrosión. Se han obtenido recubrimientos inorgánicos e híbridos de distintas composiciones sobre distintos metales usando técnicas como inmersión, centrifugado y pulverización. Aunque estos métodos proporcionan recubrimientos con buenas

B. FERRARI; R. MORENO; A. dURÁN

442

Sol-Gel Glass Solid State Lasers Doped With Organic Molecules.  

National Technical Information Service (NTIS)

When doped with organic dye laser molecules, porous sol-gel prepared silica constitutes a solid state dye laser medium. In this study such media have been shown to exhibit laser action using: (a) a krypton fluoride, 249nm, laser pump producing nanosecond ...

C. Whitehurst D. J. Shaw T. A. King

1992-01-01

443

Comparative Studies of PST Thin Films as Prepared by Sol-Gel, LDCVD and Sputtering Techniques  

Microsoft Academic Search

Lead scandium tantalate (PST) thin films for pyroelectric applications have been deposited by using liquid delivery chemical vaporise deposition (LDCVD), sputtering and sol-gel techniques. These films were annealed by using rapid thermal annealing to improve their electrical properties. Their microstructures and electrical properties such as permittivity l r , dielectric loss tan i , pyroelectric coefficient p, and thermal detection

Z. Huang; P. P. Donohue; Q. Zhang; D. Williams; C. J. Anthony; M. A. Todd; R. W. Whatmore

2002-01-01

444

A Sol-Gel-Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall  

SciTech Connect

A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA microchip. The water contact angle for the sol-gel-modified PMMA was 27.4° compared with 66.3° for the pure PMMA. In addition, the electro-osmotic flow increased from 2.13×10-4 cm2 V-1 s-1 for the native-PMMA channel to 4.86×10-4 cm2 V-1 s-1 for the modified one. The analytical performance of the sol-gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m-1 compared with 14 730.5 m-1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.

Chen, Gang; Xu, Xuejiao; Lin, Yuehe; Wang, Joseph

2007-07-27

445

Thio sol-gel process for the synthesis of titanium disulfide  

Microsoft Academic Search

Sulfides of transition metals (titanium, molybdenum, vanadium, tungsten, etc.) represent an important class of materials well-known for their catalytic and electrochemical properties. The catalytic properties make them potentially useful in hydrodesulfurization reactions, and their electrochemical response makes them suitable as active cathodes in rechargeable batteries. A thio sol-gel process for the synthesis of titanium disulfide using titanium alkoxide as the

Mandyam A. Sriram; Prashant N. Kumta

1994-01-01

446

Preparation of UO sub 2 Dense Spherical Particles by Sol-Gel Technique.  

National Technical Information Service (NTIS)

The results of the basic research and development of processes of preparation of dense UO sub 2 spherical particles by sol-gel technique are presented. Attention was paid to the study of chemistry of internal gelation step in the uranyl nitrate-urea-hexam...

V. Urbanek J. Dolezal

1977-01-01

447

Sol-gel coating of inorganic nanostructures with resorcinol-formaldehyde resin.  

PubMed

A general sol-gel process has been developed to form a coating of resorcinol-formaldehyde (RF) resin on inorganic nanostructures of various compositions and morphologies. The RF shell can be conveniently converted into carbon through high temperature carbonization under an inert atmosphere. PMID:23515396

Li, Na; Zhang, Qiao; Liu, Jian; Joo, Jibong; Lee, Austin; Gan, Yang; Yin, Yadong

2013-06-01

448

Synthesis of Alumina-Zirconia Powders by Sol-Gel Processing.  

National Technical Information Service (NTIS)

The object of this investigation is to determine the feasibility of sol-gel processes for preparing powders of phase-stabilized zirconia. Composites of phase-stabilized zirconia and alumina in which fracture toughening is achieved by the tetragonal to mon...

W. D. Bond P. F. Becher

1987-01-01

449

Improving the temperature performance of low-density ceramic heatshields through sol-gel processing  

NASA Technical Reports Server (NTRS)

The performance of rigid insulations for use as thermal protection materials on reentry vehicles can be characterized by their resistance to dimensional and morphological change when exposed to an isothermal environment equivalent to that generated in entry. Improvements in these material characteristics for alumina-enhanced thermal barrier insulation by compositional modification through sol-gel processing are reported.

Bull, Jeffrey; Leiser, Daniel; Sommers, Jeneen; Esfahani, Lili

1991-01-01

450

Pressureless sintering of sol-gel derived alumina–zirconia composites  

Microsoft Academic Search

Alumina–zirconia (pure zirconia, 12 mol % ceria stabilized zirconia and 3 mol% yttria stabilized zirconia) composites containing 5, 10, 15, 20 and 25 vol.% zirconia were prepared by sol-gel technique. The procedure involved the following steps: preparation of stable (hydrous) alumina and zirconia sols, mixing of sols in proper ratio, to obtain the final precursor with the desired composition and

Doni Jayaseelan; Tadahiro Nishikawa; Hideo Awaji; F. D Gnanam

1998-01-01

451

Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol–gel process  

Microsoft Academic Search

Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr6+ has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol–gel process. In this study, Ytttria and Yttria

M. A. Domínguez Crespo; A. García Murillo; A. M. Torres-Huerta; F. de. J. Carrillo-Romo

2009-01-01

452

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.

2012-01-01

453

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

454

Sol-gel composite hydrothermal processing of barium strontium titanate films for microwave frequency applications  

NASA Astrophysics Data System (ADS)

Stoichiometric barium strontium titanate (BST) films of composition Ba 0.7Sr0.3TiO3 with thickness >2mum have been fabricated on various substrates including Si/SiO2/Pt and Al 2O3/Au by hydrothermal sol-gel composite processing. This film deposition technique involves the treatment of a spun-on sol-gel composite film in an alkaline aqueous solution at temperatures from 50-200°C and pressures of 1-15 atm. An initial hydrolysis procedure eliminates dissolution of the dried sol-gel prior to hydrothermal processing. Glancing angle x-ray diffraction shows excellent crystallinity and stoichiometry in the BST films. Scanning electron micrography, atomic force microscopy, and transmission electron microscopy are used to examine the microstructure of the films. Both the film morphology and electrical studies suggest that the microstructure of the films evolves by nucleation and growth of the sol-gel-derived BST on the underlying powder, resulting in an interconnected microstructure in which the sol-gel-derived material forms bridges between the original powder particles. The relative dielectric constant and loss tangent of the BST films are measured in the frequency range from 1 to 100 kHz using parallel plate capacitors. Changes in the electrical characteristics of the film upon variation of hydrothermal process parameters including temperature, process duration, and the concentration of the hydrothermal solution are examined. At 100 kHz relative permittivities of the films range from epsilonr = 400-1200 and loss tangents lie in the range 0.05 < tan delta < 0.10, depending on the parameters of preparation. Complex impedance analysis is used to examine the varying bulk and grain boundary contributions to the total film behaviour. BST pellets of various thicknesses have also been produced. These pellets are impregnated with BST sol-gel which is subsequently hydrothermally processed. The electrical characteristics of the pellets are evaluated and explained in terms of the degree of penetration of the sol-gel into the pellets. The relative dielectric constant and loss tangent of the films between 5 and 40 GHz are determined using a set of coplanar waveguides with spur-line filters. The maximum relative dielectric permittivity at 40 GHz was found to be 94. The loss tangent of the film was found to increase from 3.5% to 6.0% from 10-15 GHz. The permittivity of the films from 1 kHz to 40 GHz is explained in terms of a fractal description of the film microstructure.

Zelonka, Kim

455

rhEGF-containing thermosensitive and mucoadhesive polymeric sol-gel for endoscopic treatment of gastric ulcer and bleeding.  

PubMed

Gastrointestinal endoscopy is a standard diagnostic tool for gastrointestinal ulcers and cancer. In this study, we have developed recombinant human epidermal growth factor-containing ulcer-coating polymeric sol-gel for endoscopic application. Chitosan and pluronic F127 were employed for their thermoresponsive and bioadhesive properties. At temperatures below 21, polymeric sol-gel remains liquid during endoscopic application and transforms to gel at body temperature after application on ulcers. In an in vitro cellular wounding assay, recombinant human epidermal growth factor sol-gel significantly enhanced the cell migration and decreased the wounding area (68%) compared to nontreated, recombinant human epidermal growth factor solution, and sol-gel without recombinant human epidermal growth factor (42, 49, and 32 % decreased at day 1). The in vivo ulcer-healing study was performed in an acetic acid-induced gastric ulcer rat model and proved that our recombinant human epidermal growth factor endoscopic sol-gel facilitated the ulcer-healing process more efficiently than the other treatments. Ulcer sizes in the recombinant human epidermal growth factor sol-gel group were decreased 2.9- and 2.1-fold compared with those in the nontreated group on days 1 and 3 after ulceration, respectively. The mucosal thickness in the recombinant human epidermal growth factor sol-gel group was significantly increased compared to that in the nontreated group (3.2- and 6.9-fold on days 1 and 3 after ulceration, respectively). In a gastric retention study, recombinant human epidermal growth factor sol-gel stayed on the gastric mucosa more than 2 h after application. The present study suggests that recombinant human epidermal growth factor sol-gel is a prospective candidate for treating gastric ulcers via endoscopic application. PMID:23942163

Maeng, Jin Hee; So, Jung Won; Kim, Jungju; Kim, In Ae; Jung, Ji Hoon; Min, Kyunghyun; Lee, Don Haeng; Yang, Su-Geun

2014-03-01

456

Sol-gel processes and materials. November 1971-October 1989 (Citations from the US Patent data base). Report for November 1971-October 1989  

SciTech Connect

This 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, cataylsts and catalyst supports, nuclear fuels preparation, abrasives for grinding wheels, sol-gel production of microspheres, alumina composites, photographic materials, and dental materials. (This updated bibliography contains 120 citations, 12 of which are new entries to the previous edition.)

Not Available

1990-01-01

457

A fiber-optic pH sensor prepared using a base-catalyzed organo-silica sol–gel  

Microsoft Academic Search

Fiber-optic pH sensors have been fabricated using fluorescein isothiocyanate immobilized in a base-catalyzed organo-silica sol–gel film. Hydrophilic sol–gel coatings are made by co-polymerizing tetraethylorthosilicate and silanol-terminated polydimethylsiloxane with 3-aminopropyltriethoxysilane (APTES) and\\/or 3-glycidoxypropyltrimethoxysilane. Unlike current techniques, which describe acid-catalyzed sol–gels, a base catalyst was found to be better suited for producing optically transparent gels when high concentrations of APTES were used.

Delana A Nivens; Yunke Zhang; S. Michael Angel

1998-01-01

458

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

459

Sol-gel synthesis of nanocomposite materials based on lithium niobate nanocrystals dispersed in a silica glass matrix  

SciTech Connect

With the final goal to obtain thin films containing stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol-gel route to prepare nanocomposite materials in the Li{sub 2}O-Nb{sub 2}O{sub 5}-SiO{sub 2} system is reported. In this route, LiNO{sub 3}, NbCl{sub 5} and Si(OC{sub 2}H{sub 5}){sub 4} were used as starting materials. The gels were annealed at different temperatures and nanocrystals of several phases were formed. Futhermore, by controlling the gel compositions and the synthesis parameters, it was possible to obtain LiNbO{sub 3} as only crystallizing phase. LiNbO{sub 3}-SiO{sub 2} nanocomposite thin films on Si-SiO{sub 2} and Al{sub 2}O{sub 3} substrates were grown. The LiNbO{sub 3} average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li{sub 2}O-10Nb{sub 2}O{sub 5}-80SiO{sub 2} heated 2 h at 800 deg. C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current-voltage curves. - Graphical abstract: Sol-gel synthesis of nanocomposite materials in the Li{sub 2}O-Nb{sub 2}O{sub 5}-SiO{sub 2} system is reported. The goal was to synthesize thin films containing lithium niobate nanocrystals embedded in a silica matrix. Starting from LiNO{sub 3}, NbCl{sub 5} and Si(OC{sub 2}H{sub 5}){sub 4,} it was possible to obtain LiNbO{sub 3} as only crystallizing phase, nanocrystals size was 27 nm for a film 10Li{sub 2}O-10Nb{sub 2}O{sub 5}-80SiO{sub 2} heated 2 h at 800 deg. C.

Marenna, Elisa [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, 80125 Napoli (Italy); Aruta, Carmela [CNR-INFM Coherentia e Dipartimento di Fisica, Universita di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cintia, 80126 Napoli (Italy); Fanelli, Esther [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, 80125 Napoli (Italy); Barra, Mario [CNR-INFM Coherentia e Dipartimento di Fisica, Universita di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cintia, 80126 Napoli (Italy); Pernice, Pasquale [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, 80125 Napoli (Italy); Aronne, Antonio, E-mail: anaronne@unina.i [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, 80125 Napoli (Italy)

2009-05-15

460

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

461

Elaboration et caracterisation de poudres d'oxyde d'yttrium et d'oxyde d'hafnium par procedes sol-gel. (Elaboration and characterisation of yttrium oxide and hafnium oxide powders by the sol-gel process).  

National Technical Information Service (NTIS)

The two classical sol-gel processes, colloidal and polymeric are studied for the preparation of yttrium oxide and hafnium oxide high performance powders. In the colloidal process, controlled and reproducible conditions for the preparation of yttrium oxide...

T Hours

1988-01-01

462

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

463

Advantages of the pre-immobilization of enzymes on porous supports for their entrapment in sol-gels.  

PubMed

In this work, we have compared the entrapment of free or previously immobilized glucose oxidase using a sol-gel technique. The preimmobilization was carried out on Sepabeads (a porous support) derivatized with glutaraldehyde as the functional group. The prior immobilization of the enzyme permitted to maintain the enzyme activity intact after the formation of the sol-gel. In fact, only 10% of the enzyme activity was lost whereas the soluble enzyme lost 60% of its initial activity. Additionally, enzyme leakage from the sol-gel matrix was avoided, which was relatively high when entrapping the soluble enzyme (39% of the enzyme activity was released after 16 h of incubation in a buffered solution). Moreover, the immobilized enzyme, inside the porous support, cannot be in contact with the sol-gel, and, therefore, it maintained the stability achieved by means of the multipoint covalent attachment on the Sepabeads support. PMID:15762674

Betancor, Lorena; López-Gallego, Fernando; Hidalgo, Aurelio; Fuentes, Manuel; Podrasky, Ondrej; Kuncova, Gabriela; Guisán, José M; Fernández-Lafuente, Roberto

2005-01-01

464

Synthesis of the Nanocrystalline Nickel Ferrite by a Novel Mechano Sol-Gel Auto-Combustion Method  

NASA Astrophysics Data System (ADS)

In this work, a novel method of mechano sol-gel auto-combustion has been developed for production of single phase nickel ferrite nanocrystalline powder, consisting of a sol-gel auto-combustion synthesis followed by a high energy milling process before calcination. Sol-gel auto-combustion was carried out using a gel including citric acid as a reductant and metal nitrates as oxidants. This gel exhibited a self-propagating behavior after ignition in air. The effects of the intermediate high energy milling on the physical properties of the final product after calcination were investigated. The results showed that with a high energy milling of the sol-gel auto-combusted powders with a ball-to-powder mass ratio of 20 for 20 h, the temperature of calcination for synthesis of the single phase ferrite reduced from 1000°C to 700°C and the size of the ferrite crystallites decreased from 72 nm to 15 nm.

Shahmirzaei, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

465

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

466

Photodynamic Protein Incorporated in Conducting Polymer and Sol-Gel Matrices: Toward Smart Materials for Information Storage and Processing.  

National Technical Information Service (NTIS)

We report our development of biomaterials for information processing and signal transduction by incorporation of photodynamic proteins into conducting polymer and sol-gel matrices. Our aim is to develop biomaterials with high optical quality, good thermal...

Z. Chen K. G. Chittibabu K. A. Marx S. K. Tripathy L. A. Samuelson

1994-01-01

467

Status of Experimental Studies on the Sol-Gel Synthesis of Ceramic Powders for High-Strength Ceramic Materials Applications.  

National Technical Information Service (NTIS)

Sol-gel processes are being investigated to prepare sinterable ceramic powders of alumina toughened with 10 to 30 vol % phase-stabilized zirconia and of alumina reinforced with silicon carbide whiskers. Two approaches are under investigation for the synth...

W. D. Bond G. D. Davis P. Angelini P. F. Becher T. N. Tiegs

1987-01-01

468

Silicon diffusion in sol-gel derived isotopically enriched silica glasses  

SciTech Connect

We performed silicon diffusion experiments with sol-gel derived isotopically enriched silica glasses at temperatures between 1050 deg. C and 1300 deg. C. The diffusion profiles were measured by means of time-of-flight secondary ion mass spectrometry. Samples annealed in closed silica ampoules under argon or dry air reveal enhanced Si diffusion compared to Si diffusion in fused silica. On the other hand, annealing in a large alumina tube under {sup 18}O{sub 2} ambient yields Si and O diffusion coefficients which approach the results for thermally grown SiO{sub 2}. The enhanced Si diffusion in sol-gel derived glass is proposed to be due to water residues which lead to the formation of silanol SiOH groups.

Bracht, H.; Staskunaite, R.; Haller, E.E.; Fielitz, P.; Borchardt, G.; Grambole, D. [Institute of Material Physics and Sonderforschungsbereich 458 and Center of Nanotechnology (CeNTech), University of Muenster (Germany); Institute of Metallurgy, Technical University of Clausthal (Germany); Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf (Germany)

2005-02-15

469

Sol-gel optical coatings processed by the 'laminar flow coating' technique  

NASA Astrophysics Data System (ADS)

We describe a new coating technique of laminar flow coating (LFC) developed to obtain highly reflective (HR) laser damage resistant sol-gel multidielectric coatings. Such coatings are used in high-power lasers for inertial confinement fusion experiments (ICF). This technique uses substrates in an upside-down position and a traveling wave of coating solution is laminary transported under the substrate surface with a tubular dispense unit. This creates a thin-film coating by the solvent evaporation. Satisfactory results have been obtained onto 20 cm square glass substrates regarding the optical performances, the thickness uniformity, the edge-effects and the laser damage resistance. This deposition technique combines the advantages of both classical techniques: the substrate nonexclusive geometry such as in dip- coating and the small solution consumption such as in spin-coating. The association of sol-gel colloidal suspensions and LFC coating process has been demonstrated as a promising way to produce cheap specific optical coatings.

Belleville, Phillippe F.; Floch, Herve G.; Berger, Michel

1992-12-01

470

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

471

Cotton Fabric Surface Modification by Sol-Gel Deposition of ZnO Thin Films  

NASA Astrophysics Data System (ADS)

One of the main tasks of research is to impact the additional value on natural textiles by adding to them ultraviolet (UV) absorption and antimicrobial protection properties with ZnO nano-level coatings. ZnO shows high absorption in the UV region of the light spectrum, in comparison with organic absorbers conventionally used in the textile industry shows no significant degradation, is stable and classified as non-toxic material. Nanosols were prepared by using the sol-gel process. In this work comparison of samples coated by nanosols with zinc acetate (Zn (CH3COO)2-2H2O) and zinc sulphate (ZnSO4) was made. Scanning electron microscopy (SEM) was used to examine the nature of the surface modification with ZnO coating by the sol-gel technique as also after exploitation of samples; energy dispersive X-ray spectroscopy was used for the analysis of elemental composition of coated fabric samples.

Vihodceva, S.; Kukle, S.

2012-08-01

472

A sol-gel based surface treatment for preparation of water repellent antistatic textiles  

NASA Astrophysics Data System (ADS)

In this paper a surface treatment is described for preparation of hydrophobic sol-gel coatings that simultaneously offer antistatic properties for an appropriate finishing of textiles and refinement of polymer foils. Sol-gel based formulations are modified with both hydrophilic and hydrophobic components simultaneously. Hydrophobic components are, e.g., alkoxysilanes modified with alkyl chains while the hydrophilic ones are amino-functionalized alkoxysilanes. The basic idea is that due to an enrichment of hydrophobic groups at the solid/air interface the surface of the as prepared coatings will be hydrophobic while the deeper region will be more hydrophilic. Textiles finished with these coatings exhibit sufficient water repellence and simultaneously absorb sufficient amounts of humidity in the deeper areas of the coating guaranteeing antistatic properties. This concept offers interesting approaches for the preparation of multifunctional surface coatings not only focussing on combining water repellence with antistatic properties for textile materials.

Textor, Torsten; Mahltig, Boris

2010-01-01

473

Photochemical reduction of methyl viologen in silicate xerogels obtained by the sol gel process  

NASA Astrophysics Data System (ADS)

Mixture of ruthenium (II) tris-bipyridine complex (Ru(bpy) 32+ — photosensitizer), methyl viologen (MV 2+ — electron acceptor) and EDTA (sacrificial electron donor) has been immobilized in silicate xerogels obtained by the sol-gel technique. Mixtures of Ru(bpy) 32+, MV 2+ and EDTA are capable of formation of the blue photoreduced MV rad + cation radical in aqueous solutions upon UV (around 280 nm) or visible (around 450 nm) excitations. However, when entrapped in silicate xerogels they do not exhibit blue coloration at all. On the other hand, UV excitation of xerogels doped only with MV 2+ results in appearance of blue color indicative of the paraquat photoreduction. It has been shown that in the case of the xerogel-entrapped methyl viologen the source of the reducing photoelectron is ethanol. The alcohol molecules are produced during the tetraethoxysilane (precursor) hydrolysis step of the silicate matrix production occurring via the sol-gel process.

Maruszewski, Krzysztof; Jasiorski, Marek; Hreniak, Dariusz; Str?k, Wies?aw

2001-10-01

474

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

475

Optical and electrochromic properties of sol-gel-deposited tungsten oxide films  

NASA Astrophysics Data System (ADS)

The electrochromic properties of sol-gel and mesoporous tungsten oxide thin films were investigated. Tungsten oxide films were prepare