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1

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

2

Synthesis of Carbon Nanotubes Using Sol Gel Route  

NASA Astrophysics Data System (ADS)

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

Abdel-Fattah, Tarek

2002-12-01

3

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

4

SOL - GEL CHEMICAL ROUTES FOR PREPARING BIOACTIVE FLUORHYDROXYAPATITE THIN FILMS AND POWDERS  

Microsoft Academic Search

Bioactive apatite materials are usually used as coatings onto surface of biocompatible metals, leading to implants which take advantage of the coating's bioactivity and good mechanical properties of metals. Until recently the most prominent bioactive coating was hydroxyapatite (HA). In this work, powders and apatite type films were prepared on Ti6Al4V medical grade alloy using three sol-gel chemical routes by

G. E. Stan; J. M. F. Ferreiraa

5

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

6

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

7

Synthesis of (Pb,La) (Zr,Ti)O3 films using a diol based sol–gel route  

Microsoft Academic Search

Morphotropic phase boundary compositions of lead zirconate titanate (PZT) modified with 2, 5 and 10 mol% lanthanum (PLZT) have been prepared using a diol based sol–gel route. Thin films of these PLZT compositions were fabricated on platinized silicon substrates by a spin coating technique. The effects of firing temperature and lanthanum modifications were investigated with regard to phase development, microstructure,

R. Kurchania; S. J. Milne

1998-01-01

8

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

PubMed Central

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

Martinelli, Anna

2014-01-01

9

Sol-gel microencapsulation of odorants and flavors: opening the route to sustainable fragrances and aromas.  

PubMed

The sol-gel approach to encapsulate fragrance and aroma chemicals in porous silica-based materials has the potential to afford odorant and flavoured materials with novel and unique beneficial properties. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, we show how different synthetic strategies afford advanced materials suitable for practical application with important health and environmental benefits. PMID:24077399

Ciriminna, Rosaria; Pagliaro, Mario

2013-12-21

10

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. PMID:23512012

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

2013-01-01

11

Residual stress study of nanostructured zirconia films obtained by MOCVD and by sol-gel routes  

NASA Astrophysics Data System (ADS)

The residual stress study of nanostructured zirconia films obtained by two deposition techniques, MOCVD and sol-gel used in this work, shows the advantages and limitations of each process. The MOCVD technique allows obtaining dense and thick zirconia films. Sol-gel deposition led to thinner zirconia films compared to those obtained by MOCVD, but the possible control of deposition parameters including multi-layers deposition is an advantage for the development of dense and homogeneous zirconia films. The crystalline structures and residual stress levels of nanostructured films have been studied by X-ray diffraction method; the film morphology has been analyzed by FEG-MEB.

Jouili, M.; Andrieux, M.; Ribot, P.; Bleuzen, A.; Fornasieri, G.; Ji, V.

2013-07-01

12

Two-layer light emitting diodes prepared by the sol gel route  

NASA Astrophysics Data System (ADS)

We have elaborated organic-inorganic hybrid light-emitting diodes (HLED). These devices emitting in the green are formed of two hybrid thin layers, exhibiting different functionalities, which are sandwiched between indium-tin oxide (ITO) and metallic electrodes. These layers have been prepared from silane precursors modified with hole transporting units and light-emitting naphthalimide moieties by the sol-gel technique. The hole transporting sol-gel layers exhibit about the same charge mobility as organic polymers having equivalent active units. The maximum external quantum efficiency of the best diode using LiF/Al cathode is about 1% and the luminance reaches 4000 cd · m -2 .

Dantas De Morais, Tony; Chaput, Frederic; Boilot, Jean-Pierre; Lahlil, Khalid; Darracq, Bruno; Lévy, Yves

2000-05-01

13

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

SciTech Connect

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

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

2012-11-15

14

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

15

Low-temperature deposition of the high-performance anatase-titania optical films via a modified sol gel route  

NASA Astrophysics Data System (ADS)

Anatase-titania films with high optical performances have been deposited via a modified sol-gel route. This involved several precisely controlled processes including a sufficient hydrolysis of titanium tetraisopropoxide (TTIP) with excessive water, a peptization at pH value of 1-2, a restrained condensation under the hydrothermal conditions at 373 K, and finally a spin-coating process at 293 K. A full characterization of the sols and films indicated that such a well-controlled hydrolysis and condensation of TTIP enabled the formation of high-quality precursor sols consisting of anatase-titania colloidal particles with the mean hydrodynamic diameter of about 17.2 nm, and then endowed the as-deposited films with nanocrystalline structure and the corresponding high refractive index of 1.92 (at 632.8 nm). Moreover, the prepared films exhibited large optical bandgap of 3.38 eV and high laser-induced damage threshold of 16.3 J/cm 2 (at 1064 nm, 3 ns pulse duration and R/1 testing mode), which must be closely related to their homogeneous and nearly defect-free network structures derived from the low-temperature sol-gel deposition route.

Sheng, Yonggang; Liang, Liping; Xu, Yao; Wu, Dong; Sun, Yuhan

2008-04-01

16

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

17

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

PubMed

Aluminosilicates with varying Al2O3:SiO2 molar ratios (3:1, 3:2, 3:3 and 3:4) have been synthesized using a hybrid sol-gel route using boehmite sol as the precursor for alumina and tetraethyl orthosilicate (TEOS) as the precursor for silica. The synthesis of boehmite sol from aluminium nitrate, and its use as the alumina precursor, is cost effective compared to alkoxide precursors. Structural aspects, including bonding and coordination, are studied in detail for samples calcined in the temperature range 400-1400 °C using both NMR and FTIR spectroscopy: the results are correlated with phase formation data (spinel and high temperature phases) obtained from XRD and thermal analysis. FTIR results show a broadening of peaks at 800 °C indicating a disordered distribution of octahedral sites caused by crosslinking between AlO6 octahedral and SiO4 tetrahedral units prior to the formation of mullite. (27)Al MAS NMR spectra are consistent with a progressive decrease in the number of AlO6 polyhedra with increasing temperature corresponding to Al in these units being forced to adopt a tetrahedral coordination due to the increasing presence of similarly coordinated Si species. XRD results confirm the formation of pure mullite at 1250 °C for a 3Al2O3:2SiO2 system. At 1400 °C, phase pure mullite is observed for all compositions except 3Al2O3:SiO2 where ?-Al2O3 is the major phase with traces of mullite. The synthesis of aluminosilicates through a hybrid sol-gel route and the detailed insight into structural features gained from spectroscopic and diffraction techniques contributes further to the development of these materials in applications ranging from nanocatalysts to high-temperature ceramics. PMID:20411190

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

2010-06-01

18

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

SciTech Connect

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

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

2005-02-11

19

Effects of the sol-gel route on the structural characteristics and antibacterial activity of silica-encapsulated gentamicin.  

PubMed

The effects of sol-gel processes, i.e., acid-catalyzed gelation, base-catalyzed gelation and base-catalyzed precipitation routes, on the encapsulation of gentamicin were investigated. The resulting xerogels were characterized using a series of complementary instrumental techniques, i.e., the adsorption/desorption of nitrogen, small-angle X-ray scattering, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The encapsulated gentamicin samples were tested against a series of Gram-positive and Gram-negative bacterial strains. The best antimicrobial activity was observed with the encapsulated gentamicin that was prepared via the precipitation route, even in comparison with the neat antibiotic, especially in the case of the Gram-positive strain Staphylococcus aureus. The gentamicin concentration on the outermost surface and the zeta potential were identified as factors that affected the highest efficiency, as observed in the case of encapsulation via the base-catalyzed process. PMID:24572495

Corrêa, G G; Morais, E C; Brambilla, R; Bernardes, A A; Radtke, C; Dezen, D; Júnior, A V; Fronza, N; Santos, J H Z Dos

2014-04-01

20

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

PubMed

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

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

2014-11-01

21

Deposition and interface structures of YBCO thin films via a non-fluorine sol-gel route  

NASA Astrophysics Data System (ADS)

Previous work on YBa 2Cu 3O x (YBCO) thin films deposited by fluorine-based sol-gel synthesis has been extensively reported. To further develop grain-textured YBCO thin films for conductor development, we deposited, via a fluorine-free sol-gel synthesis, YBCO thin films on single crystal substrates of yttrium-stabilized zirconia (YSZ) and LaAlO 3 (LAO). Sol-gel-derived films on the YSZ and LAO substrates exhibited epitaxial growth. This result was confirmed by both X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). A transport Jc above 10 5 A/cm 2 has been reached at 77 K and zero magnetic field. Experimental details are reported on the sol-gel synthesis, XRD and HRTEM characterization of the YBCO thin films. Also discussed is the underlying crystallization mechanism of the YBCO phase on these substrates.

Shi, Donglu; Xu, Yongli; Wang, S. X.; Lian, J.; Wang, L. M.; McClellan, Shaun M.; Buchanan, Relva; Goretta, K. C.

2002-06-01

22

Synthesis of Nanostructured and Nanoporous TiO2AgO Mixed Oxide Derived from a Particulate Sol-Gel Route: Physical and Sensing Characteristics  

Microsoft Academic Search

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

M. R. Mohammadi; D. J. Fray

2011-01-01

23

Phase Analysis and Oxygen Storage Capacity of Ceria-Lanthana-Based TWC Promoters Prepared by Sol-Gel Routes  

NASA Astrophysics Data System (ADS)

Ceria-lanthana-based promoters of three-way catalysts are synthesized by two different sol-gel routes, involving nitrate precursors. The oxygen uptake ability of these compounds is measured by O2 chemisorption. The specific surface area is determined by N2 adsorption (BET). X-ray diffraction data are analyzed by Rietveld refinement, demonstrating that lanthanum forms solid solution with CeO2; its total amount in ceria depends on the competitive formation of La-Al mixed oxides and on the synthetic method. The O2 uptake ability is essentially determined by the La content in the ceria-lanthana solid solution, while it is independent on the surface area and on the CeO2 particle size. The O2 uptake ability increases with the La:Ce relative amount in the ceria-lanthana solid solution, but decreases beyond a La:Ce molar ratio greater than ?0.18. This behavior is ascribed to the stable association of vacancy-vacancy or vacancy dopant cation.

Deganello, Francesca; Martorana, Antonino

2002-02-01

24

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

NASA Astrophysics Data System (ADS)

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

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

1998-07-01

25

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

26

Synthesis of Nanostructured and Nanoporous TiO 2 AgO Mixed Oxide Derived from a Particulate Sol-Gel Route: Physical and Sensing Characteristics  

Microsoft Academic Search

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).\\u000a Titanium tetraisopropoxide and silver nitrate were used as precursors, and hydroxypropyl cellulose was used as a polymeric\\u000a fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy\\u000a (FTIR) revealed that the

M. R. Mohammadi; D. J. Fray

2011-01-01

27

The sol-gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers  

NASA Astrophysics Data System (ADS)

Sol-gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol-gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttria-stabilized-zirconia (YSZ, 8% Y2O3) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 ?m thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 °C.

Viazzi, Céline; Rouessac, Vincent; Lenormand, Pascal; Julbe, Anne; Ansart, Florence; Guizard, Christian

2011-03-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

29

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

SciTech Connect

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., E-mail: y-goswami@yahoo.com; Kumar, Vijay, E-mail: y-goswami@yahoo.com [School of Physical Sciences, ITM University, Sithouli, Gwalior- 474001 (India); Sharma, Ranjana [Institute of Technology and Management, Sithouli, Gwalior- 474001 (India); Singh, Rajeev [Institute of Information Technology and Management, Sithouli, Gwalior, MP 474001 (India)

2014-04-24

30

EPR investigation on synthesis of Lithium zinc vanadate using sol-gel-combustion route and its optical properties  

NASA Astrophysics Data System (ADS)

The present work describes the synthesis of Lithium zinc vanadate (LiZnVO4) nanophosphor prepared by sol-gel-combustion method and its optical properties. The prepared sample was characterized by X-ray diffraction, SEM, electron paramagnetic resonance and photoluminescence spectroscopy. X-ray diffraction study showed the formation of pure LiZnVO4 at 600 °C with distorted phenacite structure. SEM investigation revealed that the phosphor powder has spherical morphology with particle size of about 100-200 nm. EPR study showed the change of coordination sphere around vanadium from axially distorted octahedral symmetry to tetrahedral geometry along with the change in oxidation state of vanadium ion from +4 to +5. The emission spectrum showed a broad emission at 543 nm with ?ex = 375 nm. The decay time obtained on mono-exponential fitting was 8.3 ?s. The colour coordinates of the system were evaluated using CIE index diagram to be 0.31 and 0.41, which suggest that the prepared material is a potential green emitting phosphor. A bright green colour emission was also observed directly from this phosphor upon excitation with an UV source.

Pathak, Nimai; Gupta, Santosh K.; Prince, Angelina; Kadam, R. M.; Natarajan, V.

2014-01-01

31

Development of injectable biocomposites from hyaluronic acid and bioactive glass nano-particles obtained from different sol-gel routes.  

PubMed

Bioactive glass nano-powders with the same chemical composition and different particle characteristics were synthesized by acid-catalyzed (the glass is called BG1) and acid-base catalyzed (BG2) sol-gel processes. Morphological characteristics of powders were determined by TEM and BET methods. The powders were separately mixed with 3% hyaluronic acid solution to form a paste. In vitro reactivity of pastes was determined by soaking them in simulated body fluid. Rheological behaviors of paste in both rotation and oscillation modes were also measured. The results showed that BG1 particles was microporous with mean pore diameter of 1.6 nm and particle size of ~300 nm while BG2 was mesoporous with average pore diameter of 8 and 17 nm and particle size of 20-30 nm. The paste made of BG2 revealed better washout resistance and in vitro apatite formation ability than BG1. According to the rheological evaluations, both pastes exhibited shear thinning but non-thixotropic behavior, meanwhile paste of BG2 had higher viscosity than BG1. The oscillatory tests revealed that the pastes were viscoelastic materials with more viscous nature. Both pastes could be completely injected through standard syringe using low compressive load of 5-50 N. Overall, The biocomposites can potentially be used as bioactive paste for the treatment of hard and even soft tissues. PMID:23910271

Sohrabi, Mehri; Hesaraki, Saeed; Kazemzadeh, Asghar; Alizadeh, Masoud

2013-10-01

32

Structural, optical and morphological analyses of pristine titanium di-oxide nanoparticles - Synthesized via sol-gel route  

NASA Astrophysics Data System (ADS)

Pure titanium di-oxide nanoparticles (TiO2) were synthesized by sol-gel technique at room temperature with appropriate reactants. The synthesis of anatase phase TiO2 nanoparticles was achieved by tetraisopropyl orthotitanate and 2-propanol as common starting materials and the product was annealed at 450 °C for 4 h. The synthesized product was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), UV-VIS-Diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy and Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) analysis. XRD pattern confirmed the crystalline nature and tetragonal structure of synthesized composition. Average grain size was determined from X-ray line broadening, using the Debye-Scherrer relation. The functional groups present in the sample were identified by FTIR spectroscopy. Diffuse reflectance measurement indicated an absorption band edge on UV-region. The allowed direct and indirect band gap energies, as well as the crystallite size of pure TiO2 nanoparticles are calculated from DRS analysis. The microstructure and elemental identification were done by SEM with EDX analysis.

Praveen, P.; Viruthagiri, G.; Mugundan, S.; Shanmugam, N.

2014-01-01

33

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

34

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

35

Nanocrystal/sol-gel nanocomposites  

DOEpatents

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

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

2012-06-12

36

Nanocrystal/sol-gel nanocomposites  

DOEpatents

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

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

2007-06-05

37

Organic-inorganic nanocomposite materials prepared by the sol-gel route as new ionic conductors in quasi solid state electrolytes  

Microsoft Academic Search

Nanocomposite organic\\/inorganic materials made through sol-gel method exhibit high values of ionic conductivity when they\\u000a were impregnated with the redox couple I\\u000a 3\\u000a ?\\u000a \\/I? Two different kinds of nanocomposite materials, depending on the different interactions between silica and poly(ethylene)oxide\\u000a or poly(propylene)oxide blends, were prepared by the sol-gel technique in room temperature. Gels, for both nanocomposite materials,\\u000a were obtained by

Elias Stathatos

2005-01-01

38

Transparent, conducting ATO thin films by epoxide-initiated sol-gel chemistry: a highly versatile route to mixed-metal oxide films.  

PubMed

A robust synthesis approach to transparent conducting oxide (TCO) materials using epoxide assisted sol-gel chemistry is reported. The new route utilizes simple tin and antimony chloride precursors in aqueous solution, thus eliminating the need for organometallic precursors. Propylene oxide acts as a proton scavenger and drives metal hydroxide formation and subsequent polycondensation reactions. Thin films of antimony-doped tin oxide (ATO) were prepared by dip-coating of mixed metal oxide sols. After annealing at 600 °C in air, structural, electrical and optical properties of undoped and Sb-doped tin oxide films were characterized. Single layer films with 5 mol % Sb doping exhibited an optical transparency which was virtually identical to that of the plain glass substrate and an electrical resistivity of 2.8 × 10(-2) ? cm. SEM and AFM analysis confirmed the presence of surface defects and cracks which increased with increasing Sb dopant concentration. Multiple depositions of identical ATO films showed a roughly 1 order of magnitude decrease in the film resistivity after the third layer, with typical values below 5 × 10(-3) ? cm. This suggests that a second and third deposition fill up residual cracks and defects in the first layer and thus brings out the full performance of the ATO material. The epoxide-assisted sol chemistry is a promising technique for the preparation of mixed oxide thin film materials. Its superiority over conventional alkoxide and metal salt-based methods is explained in the context of a general description of the reaction mechanism. PMID:22512285

Koebel, Matthias M; Nadargi, Digambar Y; Jimenez-Cadena, Giselle; Romanyuk, Yaroslav E

2012-05-01

39

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

40

Bioactive nanocrystalline sol-gel hydroxyapatite coatings.  

PubMed

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

Chai, C S; Ben-Nissan, B

1999-08-01

41

A molecular precursor route to oxide networks and nanocomposite materials. An alternative to the sol-gel method  

SciTech Connect

Advanced solid-state materials with useful properties increasingly involve intricate 3-dimensional networks, characterized complex stoichiometries (e.g., in ceramic superconductors such as HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8-{delta}}) and/or metastable architectures (e.g., in zeolites). New generations of materials will undoubtedly result from chemically directed, low-temperature synthetic routes. Our approach involves use of synthesis, coordination chemistry, and condensation reactions for construction of novel 3-dimensional networks. Primary targets have been oxide-based materials, which are derived from tailored, oxygen-rich precursor molecules. Initial directions have been based on metal complexes of the siloxide ligand OSi(O{sup t}Bu){sub 3} and the phosphate ligand O{sub 2}P(O{sup t}Bu){sub 2}, which eliminate isobutylene and water cleanly at remarkably low temperatures (100-200{degrees}C) to form M{sub x}Si{sub y}O{sub z} or M{sub x}P{sub y}O{sub z} materials. Attempts are made to take advantage of the chemistry of network formation and the homogeneity of the resulting systems to control the course of phase transformations at higher temperatures.

Tilley, T.D.; Lugmair, C.G.; Su, Kai; Terry, K.W. [Univ. of California, Berkeley, CA (United States); [Lawrence Berkeley National Lab., CA (United States)

1997-12-31

42

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

43

Sol-gel derived sorbents  

DOEpatents

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

Sigman, Michael E.; Dindal, Amy B.

2003-11-11

44

Invited review “sol-gel” preparation of high temperature superconducting oxides  

Microsoft Academic Search

This review article focuses on the sol-gel preparation of high temperature superconducting oxides wherein different classes of gel technologies were utilized. These involve: 1) the sol-gel route based upon hydrolysis-condensation of metal-alkoxides, 2) the gelation route based upon concentration of aqueous solutions involving metal-chelates, often called as “chelate gel” or “amorphous chelate” route, and 3) the organic polymeric gel route.

Masato Kakihana

1996-01-01

45

Nanocrystal/sol-gel nanocomposites  

DOEpatents

The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO3H, --NH2, and --PO3H2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

Klimov, Victor L.; Petruska, Melissa A.

2010-05-25

46

Metal-silica sol-gel materials  

NASA Technical Reports Server (NTRS)

The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

Stiegman, Albert E. (Inventor)

2002-01-01

47

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

NASA Astrophysics Data System (ADS)

Densely packed single-crystal Bi 2Fe 4O 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 2Fe 4O 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 2Fe 4O 9 nanowires had an orthorhombic single-crystal structure. Furthermore, the energy-dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric Bi 2Fe 4O 9 was formed. The possible formation mechanism of nanowires was also discussed.

Yang, Zhi; Huang, Yi; Dong, Bin; Li, Hu-Lin; Shi, San-Qiang

2006-11-01

48

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

49

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

50

Structural, magnetic and hyperfine properties of single-phase SrFe12O19 nanoparticles prepared by a sol–gel route  

NASA Astrophysics Data System (ADS)

Single-phase nanocrystalline strontium hexaferrite (SrFe12O19) powders have been synthesized by a sol–gel method and their structural, magnetic and hyperfine properties are discussed. The optimum annealing temperature of the as-prepared gel for formation of the single-phase SrFe12O19 structure has been found to be 800 °C. X-ray diffraction and Fourier transform infrared studies confirmed formation of the hexaferrite phase. The cation distribution at crystallographic inequivalent sites of the hexaferrite structure has been examined by 57Fe Mössbauer spectroscopy and found to be identical to that reported earlier. Single-phase SrFe12O19 nanoparticles (NPs) showed a magnetic hysteresis loop with high coercivity and saturation magnetization denoting an irreversible magnetization character. The temperature dependent magnetization measurements reveal a difference between the zero-field-cooled and field-cooled curves throughout the measurement range 5–300 K that is attributed to superparamagnetic relaxation of finer hexaferrite particles and disordered spins at the surface of the NPs. Both hyperfine and magnetic studies confirm that magnetic anisotropy plays a crucial role in hexaferrite NPs.

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

2015-02-01

51

MDSC and DSC studies on sol-gel lithium triborate glass and glass-ceramics: a comparison  

Microsoft Academic Search

Glasses prepared following a sol-gel route must be thermally treated to evacuate solvent and organic radicals. They often undergo phase transitions in the same temperature range where the weight losses occur. When applied to these systems, conventional differential scanning calorimetry (DSC) may lead to deceiving interpretations. In this paper the transformations of a sol-gel lithium triborate glass, annealed up to

Corrado Tomasi; Piercarlo Mustarelli; Eliana Quartarone; Renzo Pepi

1997-01-01

52

Tough ceramic coatings: Carbon nanotube reinforced silica sol-gel  

NASA Astrophysics Data System (ADS)

Silica coatings reinforced with carbon nanotubes were produced via sol-gel route using two mixing techniques of the sol-gel precursors, mechanical and ultrasonic mixing, and dip-coating as deposition process on magnesium alloy substrates. Effective incorporation and distribution of 0.1 wt.% of carbon nanotubes in the amorphous silica matrix of the coatings were achieved using both techniques. Fabrication procedure determines the morphological aspects of the coating. Only mechanical mixing process produced coatings dense and free of defects. Nanoindentation technique was used to examine the influence of the fabrication process in the mechanical features of the final coatings, i.e. indentation fracture toughness, Young's modulus and hardness. A maximum toughening effect of about 24% was achieved in silica coatings reinforced with carbon nanotubes produced by the mechanical mixing route. Scanning electron microscopy investigation revealed that the toughening of these reinforced coatings was mainly due to bridging effect of the reinforcement.

López, A. J.; Rico, A.; Rodríguez, J.; Rams, J.

2010-08-01

53

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

54

Sol–gel preparation of bioactive apatite films  

Microsoft Academic Search

The surface of biomedical metallic implants covered by a bioactive apatite film can create bioactivity of the implant and shorten healing time. In this work, apatite films on Ti6Al4V were prepared by sol–gel route using Ca(NO3)2, P2O5 and HPF6 as the precursors, in vitro evaluations of the resulting hydroxyapatite (HA) and fluorapatite\\/hydroxyapatite solid solution (FHA) films were done in Kokubo's

Wenjian Weng; Sam Zhang; Kui Cheng; Haibo Qu; Piyi Du; Ge Shen; Jun Yuan; Gaorong Han

2003-01-01

55

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

Microsoft Academic Search

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

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

1992-01-01

56

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

NASA Astrophysics Data System (ADS)

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

Doi, Toshihiro; Soyama, Nobuyuki; Sakurai, Hideaki

2013-09-01

57

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

58

Sol-gel antireflective coating on plastics  

DOEpatents

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

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

1988-01-26

59

Sol-gel antireflective coating on plastics  

DOEpatents

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

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

1990-01-01

60

Sol-gel 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

61

The Influence of Microgravity on Silica Sol-Gel Formation  

NASA Technical Reports Server (NTRS)

We discuss space-flight experiments involving the growth of silica particles and gels. The effect of microgravity on the growth of silica particles via the sol-gel route is profound. In four different recipes spanning a large range of the parameter space that typically produces silica nanoparticles in unit-gravity, low-density gel structures were instead formed in microgravity. The particles that did form were generally smaller and more polydisperse than those grown on the ground. These observations suggest that microgravity reduces the particle growth rate, allowing unincorporated species to form aggregates and ultimately gel. Hence microgravity favors the formation of more rarefied structures, providing a bias towards diffusion-limited cluster-cluster aggregation. These results further suggest that in unit gravity, fluid flows and sedimentation can significantly perturb sol-gel substructures prior to gelation and these deleterious perturbations may be "frozen" into the resulting microstructure. Hence, sol-gel pores may be expected to be smaller, more uniform, and less rough when formed in microgravity.

Sibille, L.; Smith, D. D.; Cronise, R.; Hunt, A. J.; Wolfe, D. B.; Snow, L. A.; Oldenberg, S.; Halas, N.; Rose, M. Franklin (Technical Monitor)

2000-01-01

62

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

Microsoft Academic Search

Among other alkaline-earth aluminates, the monoclinic (M) polymorph of SrAl2O4 can be used as host material for Eu2+ 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 SrAl2?xBxO4 system (x?0.3) obtained by two different methods, a ceramic route and a modified

Purificación Escribano; Mónica Marchal; María Luisa Sanjuán; Pablo Alonso-Gutiérrez; Beatriz Julián; Eloisa. Cordoncillo

2005-01-01

63

Chemical modification of TiO2 by H2PO{4/-}/HPO{4/2-} anions using the sol-gel route with controlled precipitation and hydrolysis: enhancing thermal stability  

NASA Astrophysics Data System (ADS)

Two titanium phosphate materials (T p P and T h P) have been successfully synthesized by sol-gel route with controlled precipitation and hydrolysis. The T p P material was obtained from the reaction between precipitated titania and phosphate buffer solution H2PO{4/-} /HPO{4/2-} (pH = 7.3). The T p P material was prepared through hydrolysis of titanium in the presence of H2PO{4/-}/HPO{4/2}. The probable state of the phosphate anions in titania framework and their effect on the anatase-to-rutile transformation were characterized by ICP-AES, DTA-TG, 31P NMR, FT-IR, and Raman analysis HRTEM/SEM. FT-IR and 31P NMR analyses of titanium phosphate T p P calcined at low temperature showed that the phosphate species existed not only as Ti-O-P in the bulk TiO2 but also as amorphous titanium phosphates, including bidentate Ti(HPO4)2 and monodentate Ti(H2PO4)4. Increased calcination temperature only gave an enrichment of bidentate structure on the titania surface. For the T p P material, H2PO{4/-}/HPO{4/2-} anions were introduced into the initial solution, before precipitation, what promoted their lattice localization. At high temperatures, all the phosphorus inside the bulk of TiO2 migrated to the surface. The Raman analysis of both samples showed that the bidentate phosphates increased the temperature of the anatase-to-rutile phase transformation to more than 1000 °C with the formation of well crystalline TiP2O7 phase. This phenomenon was more evident for T p P sample.

Elghniji, Kais; Saad, Mohamed El Khames; Araissi, Manel; Elaloui, Elimame; Moussaoui, Younes

2014-12-01

64

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

65

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

66

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

67

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

68

Sol-Gel Synthesis Of Aluminoborosilicate Powders  

NASA Technical Reports Server (NTRS)

Application of sol-gel process to synthesis of aluminoborosilicate powders shows potential for control of microstructures of materials. Development of materials having enhanced processing characteristics prove advantageous in extending high-temperature endurance of fibrous refractory composite insulation made from ceramic fibers.

Bull, Jeffrey; Leiser, Daniel; Selvaduray, Guna

1992-01-01

69

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

Microsoft Academic Search

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)

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

2011-01-01

70

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

Microsoft Academic Search

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

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

2010-01-01

71

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

Microsoft Academic Search

Nanocrystalline fluoridated hydroxyapatite (FHA) powders and coatings with a chemical composition of Ca10(PO4)6OH2–x\\u000a F\\u000a x\\u000a (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\\u000a with conventional alkoxide-based sol-gel route. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transform infrared\\u000a (FTIR) spectroscopy, pF-meter

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

72

A sensitive fibre optic pH sensor using multiple sol-gel coatings  

NASA Astrophysics Data System (ADS)

The fabrication and characterization of a fibre optic pH sensor based on evanescent wave absorption is presented. The unclad portion of a multi-mode optical fibre is coated with a pH sensitive dye, which is immobilized by the sol-gel route. The sensitivity of the device has been found to increase when multiple sol-gel coatings are used as the sensing region. The dynamic range and the temporal response of the sensor are investigated for two different dyes, namely bromocresol purple and bromocresol green. The performance of the device is evaluated in terms of the results obtained during actual measurements.

Lee, S. Thomas; Gin, Jose; Nampoori, V. P. N.; Vallabhan, C. P. G.; Unnikrishnan, N. V.; Radhakrishnan, P.

2001-09-01

73

High specific surface area nickel mixed oxide powders LaNiO{sub 3} (perovskite) and NiCo{sub 2}O{sub 4} (spinel) via sol-gel type routes for oxygen electrocatalysis in alkaline media  

SciTech Connect

A novel sol-gel process of preparation of oxide electrocatalysts is investigated to prepare Ni-containing mixed oxides LaNiO{sub 3} and NiCo{sub 2}O{sub 4} at moderate temperatures. High surface area (20-55 m{sup 2} g{sup {minus}1}) powders and high roughness electrodes (30-1500) were obtained. Apparent and real electrocatalytical activity are compared and discussed.

El Baydi, M.; Chartier, P.; Koenig, J.F.; Poillerat, G. [Universite Louis Pasteur, Strasbourg (France)] [Universite Louis Pasteur, Strasbourg (France); Tiwari, S.K. [Universite Louis Pasteur, Strasbourg (France)] [Universite Louis Pasteur, Strasbourg (France); [Banaras Hindu Univ., Varanasi (India); Singh, R.N. [Banaras Hindu Univ., Varanasi (India)] [Banaras Hindu Univ., Varanasi (India); Rehspringer, J.L. [CNRS, Strasbourg (France)] [CNRS, Strasbourg (France)

1995-04-01

74

Sol-gel processing of metal sulfides  

NASA Astrophysics Data System (ADS)

Metal sulfides were synthesised via a sol-gel process using various metal alkoxides and hydrogen sulfide in toluene. Colloidal gels were prepared from germanium ethoxide, germanium isopropoxide, zinc tert-butoxide and tungsten (VI) ethoxide, whereas colloidal powder was produced from tungsten (V) dichloride ethoxide. Special precautions were necessary to protect the reaction mixture from water contamination which produced metal oxides. Results indicated that the main source of water is the hydrogen sulfide gas. In addition, synthesis of metal sulfides from a mixture of metal oxide and sulfide was demonstrated by the example of monoclinic germanium disulfide. It was produced by reaction of the sol-gel product with sulfur. Heat treatment of the sol-gel product and sulfur yielded single phase GeSsb2. The sol-gel prepared materials and their heat treated products were characterized by various methods. A chemical kinetics study of the functional groups -OR, -SH and Ssp{2-} was carried out for the sol-gel processing of GeSsb2 from of hydrogen sulfide and two different alkoxides, germanium ethoxide and germanium isopropoxide. The study was performed for different concentrations of precursors at different molar ratios and temperatures. The results indicate that the proposed reaction mechanism was simplified under appropriate reaction conditions. Experimentally determined rate constants of thiolysis and condensations demonstrate that thiolysis is slow and that condensations are fast steps, regardless of the studied reaction conditions. A study of the temperature effect on the reaction rate constant shows that it increases with temperature in accord with both Arrhenius law and transition-state theory. Activation energies, Esba, and activation parameters DeltaSsp{ddagger}, DeltaHsp{ddagger} and DeltaGsp{ddagger}, were determined for thiolysis and condensation reactions. The potentiometric tiration method was used for quantitative determination of germanium sulfide and germanium mercaptide evolved during the sol-gel processing of GeSsb2. The titrations were performed in 2-propanol or in a 50-50 vol % mixture of 2-propanol and toluene. The ion selective Ag/Agsb2S electrode was used for equivalence point detection. Study of the Nernst equation shows that complexes were formed at the electrode surface. However, the titration equivalence point volume clearly demonstrates the formation of Agsb2S and Ge(SAg)sbn. In order to explain this discrepancy a new electrode reaction mechanism and a modified Ag/Agsb2S electrode potential equation are proposed. Effects of hydrogen sulfide and germanium ethoxide concentrations, the concentration ratio and temperature on the microstructure of the prepared GeSsb2 gels were studied. It was found that the concentrations of the reactants have the most significant influence on gel structure.

Stanic, Vesha

75

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

76

Sol-gel coatings on float glass  

Microsoft Academic Search

The refractive coefficients and thickness of two-sided sol-gel coatings of different compositions deposited on float glass\\u000a by the immersion method are measured. It is established that the refractive coefficient on the top surface of a sample, which\\u000a contacts the protective atmosphere of the melt tank during glass working, is higher and the film thickness is smaller than\\u000a those on the

A. B. Atkarskaya

2006-01-01

77

Catalyst Doped Sol-Gel Materials  

Microsoft Academic Search

\\u000a An important subject in catalysis is the synthesis of metallic supported catalysts. The structural and textural modification\\u000a of this materials can improve the activity, selectivity or catalyst lifetime. Research groups have recently shown a great\\u000a interest in the preparation of metal doped catalysts by the well known sol-gel method. This process consists in the hydrolysis\\u000a and condensation of an alkoxide

Tessy López; Ricardo Gómez

78

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

79

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.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

2003-12-23

80

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

81

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

82

Neutron detector based on lithiated sol-gel glass  

Microsoft Academic Search

A neutron detector technology is demonstrated based on 6Li\\/10B doped sol-gel glass. The detector is a sol-gel glass film coated silicon surface barrier detector (SBD). The ionized charged particles from (\\/n, alpha) reactions in the sol-gel film enter the SBD and are counted. Data showing that gamma-ray pulse amplitudes interfere with identifying charged particles that exit the film layer with

Steven Wallace; Andrew C. Stephan; Laurence F. Miller; Sheng Dai

2002-01-01

83

Neutron detector based on lithiated sol–gel glass  

Microsoft Academic Search

A neutron detector technology is demonstrated based on 6Li\\/10B doped sol–gel glass. The detector is a sol–gel glass film coated silicon surface barrier detector (SBD). The ionized charged particles from (n, ?) reactions in the sol–gel film enter the SBD and are counted. Data showing that gamma-ray pulse amplitudes interfere with identifying charged particles that exit the film layer with

Steven Wallace; Andrew C Stephan; Laurence F Miller; Sheng Dai

2002-01-01

84

Sol-gel optical coatings for lasers: Part 1  

Microsoft Academic Search

Many manufacturers and users claim that optical coatings are best prepared by physical vapor deposition technology. Others believe that sol-gel technology is an effective and competitive alternative. This article, the first of three, emphasizes sol-gel thin-film history and relates it to high-power laser technology, chemistry of the sol-gel process, production of optical coatings and deposition techniques. The second and third

H. G. Floch; P. F. Belleville; J. J. Priotton; P. M. Pegon; C. S. Dijonneau; J. Guerain

1995-01-01

85

Substituent effects on the sol-gel chemistry of organotrialkoxysilanes  

SciTech Connect

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

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

2000-05-09

86

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

87

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

88

Fibrin aggregation before sol-gel transition.  

PubMed Central

Fibrinogen solutions (concentrations 2 mg/ml, 0.15-M Tris-NaCl buffer, pH 7.4) were incubated at 20 degrees C with quantities of reptilase or thrombin that were so small that the polymerization process could be followed for several hours by means of static and dynamic light scattering. The scattered intensity and its correlation function were recorded at scattering angles between 30 degrees and 150 degrees. The measured data were compared with model calculations based on the Flory-Stockmayer distribution, which predicts a sol-gel phase transition. This distribution is characterized by a parameter, lambda, that indicates the extent of aggregation. lambda = 0 corresponds to the monomeric solution, and lambda = 1 indicates the sol-gel transition. Good agreement was found for monomeric units of 75-nm length aggregating (a) end-to-end in the early stage (0 less than or equal to lambda less than or equal to 0.3), and (b) in a staggered overlap pattern for the progressing polymerization (0.3 less than or equal to lambda less than 1). Before the gel point was reached, no systemic difference was observed between the data obtained after activation with thrombin which releases both fibrinopeptides A and B from fibrinogen, and reptilase, which exclusively releases the fibrinopeptides A. This confirms that the release of the fibrinopeptides A is the essential prerequisite for the aggregation process. PMID:7093417

Wiltzius, P; Dietler, G; Känzig, W; Hofmann, V; Häberli, A; Straub, P W

1982-01-01

89

Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase  

ERIC Educational Resources Information Center

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

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

2010-01-01

90

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

SciTech Connect

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

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

2009-02-01

91

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

92

Characterization of nanostructured magnetite thin films produced by sol–gel processing  

Microsoft Academic Search

Nanocrystalline films of magnetite have been prepared by a novel sol–gel route in which, a solution of iron (III) nitrate\\u000a dissolved in ethylene glycol was applied on glass substrates by spin coating. Coating solution showed Newtonian behaviour\\u000a and viscosity was found as 0.0215 Pa.s. Annealing temperature was selected between 291 and 350 °C by DTA analysis in order\\u000a to obtain magnetite films.

Ali Erdem Eken; Macit Ozenbas

2009-01-01

93

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

94

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

95

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

96

Hybrid zirconium sol-gel thin films with high refractive index  

NASA Astrophysics Data System (ADS)

We describe the synthesis of optical quality thin film materials with high refractive index, employing zirconium based hybrid sol-gel precursors. As the zirconium propoxide precursor is unstable in the presence of a strong nucleophilic agent such as water, two synthesis routes have been performed employing a chelating agent and an organosilane precursor to avoid the formation of any undesired ZrO2 agglomerates, leading to organo-zirconate complexes and silicato-zirconate copolymers, respectively. The prepared hybrid sol-gel materials were deposited by spin-coating to form a transparent thin film on silicon substrates, and heat treated at 100 °C for the final stabilisation of the layer. The effect of the two synthesis routes on the optical properties of zirconium based hybrid sol-gel material is discussed. It was found that the nature and concentration of the organosilane precursor can significantly affect the structural properties of the deposited films. A correlation was also demonstrated between the concentration of the organosilane precursor and the refractive index of the material. By reducing the concentration of organosilane precursor, high refractive index materials were obtained. Similar behaviour was observed for the materials synthesised via chelating agent. The synthesis employing an organosilane precursor produces films with higher refractive index. A maximum refractive index of 1.746 was measured at 635nm for the deposited thin films.

Gorin, Arnaud; Copperwhite, Robert; Elmaghrum, Salem; Mc Donagh, Colette; Oubaha, Mohamed

2011-08-01

97

Phase compositions and ferroelectric properties of Pb(Zr 0.52,Ti 0.48)O 3 thin films with different highly orientations prepared by a sol-gel route  

NASA Astrophysics Data System (ADS)

It is shown that different highly oriented Pb(Zr 0.52,Ti 0.48)O 3 films can be obtained on Pt/Ti/SiO 2/Si substrate using a sol-gel technique. The effects of pyrolysis temperature on the orientation, phase composition and ferroelectric properties of the films are investigated. It is found the ferroelectric hysteresis loops of (1 1 1)-oriented film, (1 1 1) and (1 0 0) mix-oriented film can both be saturated when the external electric field is large enough, whereas the hysteresis loop of (1 0 0)-oriented film is difficult to saturate. The analysis of X-ray diffraction indicated the possibility of different phase composition in different oriented films under large film residual stress. Higher remnant polarization (53 ?C/cm 2) for (1 0 0)-oriented film can be attributed to its more tetragonal phase composition, which results in that the in-plane domain switching can continuously occur with external electric field increasing.

Chi, Q. G.; Li, W. L.; Fei, W. D.; Xu, S. C.; Feng, B.

2010-06-01

98

Effect of annealing temperature on optical properties of binary zinc tin oxide nano-composite prepared by sol-gel route using simple precursors: structural and optical studies by DRS, FT-IR, XRD, FESEM investigations.  

PubMed

Binary zinc tin oxide nano-composite was synthesized by a facile sol-gel method using simple precursors from the solutions consisting of zinc acetate, tin(IV) chloride and ethanol. Effect of annealing temperature on optical and structural properties was investigated using X-ray diffraction (XRD), diffuse reflectance spectra (DRS), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD results revealed the existence of the ZnO and SnO2 phases. FESEM results showed that binary zinc tin oxide nano-composites ranges from 56 to 60 nm in diameter at 400°C and 500°C annealing temperatures respectively. The optical band gap was increased from 2.72 eV to 3.11 eV with the increasing of the annealing temperature. FTIR results confirmed the presence of zinc oxide and tin oxide and the broad absorption peaks at 3426 and 1602 cm(-1) can be ascribed to the vibration of absorptive water, and the absorption peaks at 546, 1038 and 1410 cm(-1) are due to the vibration of Zn-O or Sn-O groups in binary zinc tin oxide. PMID:25222322

Habibi, Mohammad Hossein; Mardani, Maryam

2015-02-25

99

Effect of annealing temperature on optical properties of binary zinc tin oxide nano-composite prepared by sol-gel route using simple precursors: Structural and optical studies by DRS, FT-IR, XRD, FESEM investigations  

NASA Astrophysics Data System (ADS)

Binary zinc tin oxide nano-composite was synthesized by a facile sol-gel method using simple precursors from the solutions consisting of zinc acetate, tin(IV) chloride and ethanol. Effect of annealing temperature on optical and structural properties was investigated using X-ray diffraction (XRD), diffuse reflectance spectra (DRS), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD results revealed the existence of the ZnO and SnO2 phases. FESEM results showed that binary zinc tin oxide nano-composites ranges from 56 to 60 nm in diameter at 400 °C and 500 °C annealing temperatures respectively. The optical band gap was increased from 2.72 eV to 3.11 eV with the increasing of the annealing temperature. FTIR results confirmed the presence of zinc oxide and tin oxide and the broad absorption peaks at 3426 and 1602 cm-1 can be ascribed to the vibration of absorptive water, and the absorption peaks at 546, 1038 and 1410 cm-1 are due to the vibration of Zn-O or Sn-O groups in binary zinc tin oxide.

Habibi, Mohammad Hossein; Mardani, Maryam

2015-02-01

100

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

101

Sol-gel glasses as new waveguides for optical immunosensors  

SciTech Connect

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

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

1994-12-31

102

Failure modes of sol–gel deposited electrochromic devices  

Microsoft Academic Search

Long-term charge injection and extraction cycling performance of electrochromic devices, and the degradation of the devices has been studied. The electrochromic devices have been constructed using sol–gel deposited tungsten oxide layer, sol–gel deposited vanadium oxide layer and a polymer electrolyte. Both electrodes were cycled in a solution of 1M-LiClO4 and propylene carbonate prior to device fabrication. The devices were sealed

J. M. Bell; I. L. Skryabin

1999-01-01

103

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

104

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

105

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

106

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

107

A modified sol-gel process for multiferroic nanocomposite films  

NASA Astrophysics Data System (ADS)

Multiferroic CoFe2O4-Pb(Zr ,Ti)O3 (CFO-PZT) composite films with nanoscale mixture of the two phases were prepared by a modified sol-gel process, in which a mixed precursor solution of both CFO and PZT was used. X-ray diffraction and transmission electron microscopy examinations revealed the coexistence of perovskite PZT and spinel CFO that were mixed in nanoscale with mean grain sizes of 5-10nm. Magnetic properties of the CFO-PZT nanocomposite were examined, which were consistent with their microstructures. The magnetoelectric coupling between CFO and PZT was demonstrated by an external magnetic field induced electric polarization change. This modified sol-gel processing provides an alternative for multiferroic composite films, which is simpler and easier to control compared to the conventional layer-layer sol-gel process for multiferroic composite films.

Liu, Ming; Li, Xin; Lou, Jing; Zheng, Shijian; Du, Kui; Sun, Nian X.

2007-10-01

108

Sol–gel synthesis and characterization of the Ag 2O–SiO 2 system  

Microsoft Academic Search

Binary silver silicate (SS) (XAg2O+(1–X) SiO2; X=0.1–0.9 in steps of 0.1) system was synthesized through sol–gel route for various compositions containing SiO2 (F=SiO2) and modifier (M=Ag2O) oxides. All the synthesized SS xerogel compositions were characterized by XRD, FTIR, EDS, WDS, SEM and impedance spectroscopy techniques. The XRD spectrum showed mixed (amorphous and crystalline) phases. The formation of the SiO2 network,

N. Satyanarayana; Xiaogang Xie; B. Rambabu

2000-01-01

109

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

110

Photocatalytic activities of multiferroic bismuth ferrite nanoparticles prepared by glycol-based sol–gel process  

Microsoft Academic Search

The uniform multiferroic BiFeO3 nanoparticles with fairly narrow particle size distribution have been successfully synthesized by a simple glycol-based sol–gel\\u000a route at relatively low temperature. The thus-prepared powders were characterized by X-ray diffractometry (XRD), thermogravimetric\\u000a and differential thermal analysis (DTA\\/TG), and transmission electron microscopy (TEM). Rapid sintering and subsequently quenching\\u000a to room temperature are the two vital important factors for

X. WangY; Y. Lin; Z. C. Zhang; J. Y. Bian

111

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

112

Sol-gel processing with inorganic metal salt precursors  

DOEpatents

Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

Hu, Zhong-Cheng

2004-10-19

113

Influence of Heat Treatment on Structure and Charge Capacity of Sol-Gel Produced TiO2 Films  

NASA Astrophysics Data System (ADS)

Titanium dioxide thin films were synthesized by sol-gel route from titanium isopropoxide (TIP) with acetic acid. Prior to the heat treatment, the films were amorphous phase. Above 400 °C, phase transition took place from amorphous into anatase phase. Electrochromic properties of each phase indicated reversible coloration upon Li+ ion intercalation in cyclic voltammetric measurements. Nevertheless, both charge capacity and energy band gap of films begun to decrease with increase in annealing temperature due to the crystallization.

Özdemir, Orhan; Gökdemir, Fatma P?nar; Keskin, Bahad?r; Kutlu, Kubilay

114

Sol-gel synthesis and TEM-EDX characterisation of hydroxyapatite nanoscale powders modified by Mg, Sr or Ti  

NASA Astrophysics Data System (ADS)

Chemically modified hydroxyapatite nanoparticles have been prepared by a sol-gel route. Analysis by TEM-EDX confirmed that the dopants, Mg, Sr or Ti had been incorporated into the product. However each sample displayed variability in the level of dopant incorporation in different particles within the same sample. Particle sizes were <= 100 nm for samples modified by Mg or Ti. Doping with Sr produced an elongated particle morphology, with dimensions ~ 200nm × 50 nm.

Qaisar, S. A.; Bilton, M.; Wallace, R.; Brydson, R.; Brown, A. P.; Ward, M.; Milne, S. J.

2010-07-01

115

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

116

Sol–gel-derived organic–inorganic hybrid materials  

Microsoft Academic Search

Optically transparent organic–inorganic hybrid coating materials have been prepared by a sol–gel process. Four different types of the coating material produced by TWI in Cambridge, UK using the patented Vitresyn® method, all identical in terms of the starting materials, but differing in terms of their relative proportions, have been examined. Tetraethoxysilane was used as the primary inorganic precursor and urethane

Yung-Hoe Han; Alan Taylor; Mick D. Mantle; Kevin M. Knowles

2007-01-01

117

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

118

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

119

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

120

Sol-gel based alumina powders with catalytic applications  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

121

ARSENIC REMOVAL USING SOL-GEL SYNTHESIZED TITANIUM DIOXIDE NANOPARTICLES  

EPA Science Inventory

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

122

Design, fabrication and characterization of DWDM by sol-gel  

NASA Astrophysics Data System (ADS)

Sol-gel method of hybrid glass fabrication is investigated. A systematic method is presented and applied towards fabricating an arrayed waveguide grating (AWG). The method includes the production of a photo-mask for obtaining the resolution of waveguide fabrication and a novel method of calculation in prism coupling method. After a detailed review of the theory behind the design of AWGs, the parameters obtained from the sol-gel method are used towards a design of an AWG. Using the limits and variations in the sol-gel method a perturbation analysis is done to predict the output response of the device under these variations. The dependence of the output response to all the variations are presented. The photo-mask of an AWG layout is designed. Using the sol-gel method, the actual device is fabricated and then tested. The measured results of the fabricated AWG are within the expected and predicted range. Good insertion loss and channel isolations have been achieved. Moreover, a novel propagation method is presented and applied to extract propagation constants and the output profiles of integrated photonics devices without neither solving the wave equation nor using the paraxial approximation. By approximating the variation of the field to 4th order, this method is applied to the case of a sol-gel multimode planar waveguide. Propagation constants and output profiles are extracted and are in good agreement with the values obtained from the analytical method. The case of a full pi circular rotation of a single mode planar waveguide is also illustrated. Furthermore, a novel, low temperature, sol-gel method of fabrication for inorganic transparent films is proposed. Using this method, single-layer, crack free and transparent silica based films were fabricated. Fabrication of a silica sol-gel film with no doping produced single layer films with an average roughness of about 0.5 nm, for a surface area of 10 mum 2 was obtained. Titanium doped films for the purpose of the refractive index increase is also considered. The refractive index and the loss measurements for silica-titania films was 1.510 +/- 0.001. The infrared absorption spectra for both silica and silica-titania films are presented. The results suggest that the densification between 100°C and 150°C produces little change in quality of the material. (Abstract shortened by UMI.)

Alavian, Shahram

123

New insights into uranium (VI) sol-gel processing  

SciTech Connect

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

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

1990-01-01

124

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

125

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

126

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

127

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

128

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

129

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

SciTech Connect

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

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

2007-11-15

130

A Sol-Gel Approach to the Insulation of Rutherford Cables  

SciTech Connect

Two wind-and-react compatible variants for the electrical insulation of Rutherford cables by a sol-gel route have been investigated. The first variant involves the direct application of a sol-gel coating of SnO2-ZrO2 to the surface of the strands in the cable, whereas the second is an indirect approach consisting of coating stainless steel tapes with MgO-ZrO2 that are to be wrapped around or co-wound with the cable. Following the application of the insulation by one of the two methods, the insulation electrical resistance and breakdown voltage were determined for samples consisting of two 7 inches long cables pressed together and vacuum impregnated with epoxy (CTD-101K). With a notable exception, the breakdown voltages on directly insulated cables were too low for practical purposes. Better results, with breakdown voltages ranging from 20 to almost 200 V, were obtained for insulator coatings applied to stainless steel tapes. An additional sintering at 700-800 deg. C for 6-12h of the coatings deposited on stainless steel was found to increase the breakdown voltage.

Buta, F. [Global Research and Development, Inc., Columbus, Ohio, 43210 (United States); LASM, MSE, Ohio State University, Columbus, Ohio, 43210 (United States); Hascicek, Y.S.; Arda, L.; Aslanoglu, Z.; Akin, Y. [National High Magnetic Field Laboratory, Tallahassee, Florida, 32310 (United States); Sumption, M.D.; Collings, E.W. [LASM, MSE, Ohio State University, Columbus, Ohio, 43210 (United States)

2004-06-28

131

A Sol-Gel Approach to the Insulation of Rutherford Cables  

NASA Astrophysics Data System (ADS)

Two wind-and-react compatible variants for the electrical insulation of Rutherford cables by a sol-gel route have been investigated. The first variant involves the direct application of a sol-gel coating of SnO2-ZrO2 to the surface of the strands in the cable, whereas the second is an indirect approach consisting of coating stainless steel tapes with MgO-ZrO2 that are to be wrapped around or co-wound with the cable. Following the application of the insulation by one of the two methods, the insulation electrical resistance and breakdown voltage were determined for samples consisting of two 7 inches long cables pressed together and vacuum impregnated with epoxy (CTD-101K). With a notable exception, the breakdown voltages on directly insulated cables were too low for practical purposes. Better results, with breakdown voltages ranging from 20 to almost 200 V, were obtained for insulator coatings applied to stainless steel tapes. An additional sintering at 700-800°C for 6-12h of the coatings deposited on stainless steel was found to increase the breakdown voltage.

Buta, F.; Hascicek, Y. S.; Sumption, M. D.; Arda, L.; Aslanoglu, Z.; Akin, Y.; Collings, E. W.

2004-06-01

132

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

133

Inkjet printing of sol-gel synthesized hydrated tungsten oxide nanoparticles for flexible electrochromic devices.  

PubMed

Tungsten oxide nanoparticles were synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells. Several spectroscopic techniques were used to characterize and compare tungsten oxide particles obtained from different origins. FTIR, Raman and X-ray diffraction spectroscopic measurements showed that the sol-gel synthesis described here produces nanoparticles mainly in an amorphous state with hexagonal crystalline domains and allowed the analysis of the hydration extent of those nanoparticles. The size was measured combining dynamic light scattering, sedimentation, and microscopic techniques (AFM), showing a consistent size of about 200 nm. The tungsten oxide nanoparticles were used to produce an ink formulation for application in inkjet printing. Solid-state electrochromic devices were assembled at room temperature, without sintering the tungsten oxide printed films, showing excellent contrast between on/off states. Electrochemical characterization of those films is described using cyclic voltammetry. The devices were then tested through spectroelectrochemistry by Visible/NIR absorption spectroscopy (400-2200 nm range), showing a dual spectroscopic response depending on the applied voltage. This phenomenon is attributed to the presence of two different crystalline states in accordance with results obtained from the spectroscopic characterization of the nanoparticles. The electrochromic cells had a good cycling stability showing high reversibility and a cyclability up to more than 50,000 cycles with a degradation of 25%. PMID:22321260

Costa, Cláudia; Pinheiro, Carlos; Henriques, Inês; Laia, César A T

2012-03-01

134

Nanofiltration in non-aqueous solutions by porous silica–zirconia membranes  

Microsoft Academic Search

Porous membranes having various average pore sizes, ranging from 1 to 4nm, were prepared from silica–zirconia composite colloidal sols by sol–gel processes, and were used for nanofiltration (NF) experiments in non-aqueous solutions of ethanol and methanol. Silica–zirconia membranes, which were tested in pure alcohol solutions for the first time after the preparation of the membrane, showed a gradual decrease in

Toshinori Tsuru; Takashi Sudoh; Tomohisa Yoshioka; Masashi Asaeda

2001-01-01

135

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

136

Strategies for novel transparent conducting sol–gel oxide coatings  

Microsoft Academic Search

Transparent conducting coatings of doped SnO2 and Zn2SnO4 have been deposited by the sol–gel technique on borosilicate and alumosilicate glass substrates, respectively. As films of SnO2:Sb (ATO) show some intrinsic drawbacks, which are discussed in this report, alternative dopants for SnO2 such as Ta, Nb and W, were examined concerning the electrical and optical properties of the deposited coatings. In

A. Kurz; K. Brakecha; J. Puetz; M. A. Aegerter

2006-01-01

137

Sol-gel laser coatings at CEA Limeil-Valenton  

Microsoft Academic Search

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

Herve G. Floch; Philippe F. Belleville

1997-01-01

138

Organically modified sol–gel films incorporating an infrared dye  

Microsoft Academic Search

Steady-state absorption and emission measurements for an infrared (IR) dye have been reported. Measurements in liquid solutions and in hybrid organic\\/inorganic zirconia-based thin films synthesized with a sol–gel technique have been carried out. The optical properties of films as a function of the densification temperature have also been investigated. The results are discussed in terms of the presence of monomer

P. Prosposito; M Casalboni; F De Matteis; R Pizzoferrato

2000-01-01

139

Synthesis of zirconium oxide nanoparticle by sol-gel technique  

SciTech Connect

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

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

2013-11-27

140

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

141

Sol-gel thin films for photonic application  

NASA Astrophysics Data System (ADS)

For the fabrication of photonic devices the sol-gel technique is a potentially lucrative alternative to methods such as physical vapor or chemical vapor deposition because of its solution-processability, low cost and relative ease of production. In this work we harness this potential by developing based photonic devices which incorporate highly luminescent CdSe@ZnS core-shell semiconductor quantum dots (QDs) doped within inorganic (TiO2, ZrO2) or hybrid organic-inorganic sol-gel films. As a pre-requisite to the formation of such devices, luminescent waveguides emitting between green and red have been obtained and their optical properties have been characterized. The photochemical stability of these waveguides was found to highly dependent on the exact sol-gel material used. QDs:Titania based composites were found to be inherently photo-unstable due to photoelectron injection into the bulk matrix and subsequent nanocrystal oxidation. In comparison, zirconia composites were significantly more robust with high photoluminescence retained up to annealing temperatures of 300 °C. Despite this difference in photo-chemical stability, both titania and zirconia composite waveguides exhibited amplified stimulated emission (ASE) with one-photon and two-photon optical pumping, however only zirconia based waveguides exhibited long term photostability. This Zirconia based films have been used for the realization of distributed feedback lasers and Bragg micro-cavities.

Jasieniak, Jacek J.; Martucci, Alessandro

2012-06-01

142

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

143

Sol gel method performed for biomedical products implementation.  

PubMed

Sol-gel technology is an impressive and instructive innovation in science that necessitates a multidisciplinary approach for its important applications in the practice. An important peculiarity of the sol gel technology is the possibility to control the mechanism and kinetics of the chemical reactions, thus monitoring the final structure (particle size, porosity, thin layer thickness) of the materials. The low processing temperature combined with the intrinsic bio-compatibility and environmental friendliness of the implied components makes it an ideal method applied in different biomedical purposes: the synthesis of porous matrices for entrapping of organic and inorganic compounds, sensor molecules, enzymes and many other biological molecules, selective coatings for optical and electrochemical biosensors, stationary phases for chromatography, immunoadsorbent and solid-phase extraction materials, controlled release agents, solid-phase biosynthesis, and unique matrices for biophysical studies. It is therefore the scope of this review to provide a few insights of the recent progresses made in sol-gel-based materials for biomedical applications. PMID:20690901

Chiriac, A P; Neamtu, I; Nita, L E; Nistor, M T

2010-10-01

144

Phenyl Functionalized Sol-gel Silica Sorbent for Capillary Microextraction and Chromia-Based Sol-gel Ucon Stationary Phase for Capillary Gas Chromatography  

NASA Astrophysics Data System (ADS)

The first chapter of this thesis presents an introduction to sol-gel methodology whose usefulness as a synthetic route will be demonstrated with two applications in chromatography. The first application involves the fabrication of a capillary micro-extraction (CME) device by coating a phenyl functionalized extracting phase on the inner surface of a fused silica capillary for analyte pre-concentration. The device was coupled on-line to a RP-HPLC system and practicality was demonstrated using allergens as target analytes. The allergens chosen as model analytes are typically found in fragrance products and food. Most of the 26 fragrance allergens that are monitored by various government authorities have a phenyl organic moiety (a strong chromophore), thus making them appropriate probes for exploring the extraction efficiency of the coating using a UV detector. The CME device showed ppt level limit of detection which makes it suitable for trace analyses of allergens and similar compounds in a variety of matrices. The second application explores the feasibility of using sol-gel derived chromia-based stationary phase in gas chromatographic columns. The organic moiety of the stationary phase was derived from Ucon 75-H-90,000 while the inorganic backbone was prepared using chromium(III) dichloride hydroxide - methacrylic acid - aqua complex, 40% in isopropanol/acetone . Usefulness of prepared chromia-based GC stationary phase was examined for petrochemical application. Promising results were obtained using aliphatic-aromatics, polyaromatic hydrocarbons, BTEX test mixture, cycloalkanes, branched alkanes and akylbenzenes. The column was able to perform without degradation despite being rinsed multiples times sequentially with the following solvents: dichloromethane, methanol, water and finally methanol again. Maximum theoretical plate number calculated is around 2,400 plates/m. The plate number clearly needs improvement but is a promising result for the newly explored chromia-based stationary phase. The maximum programmable temperature is 250°C which is comparable with similar commercially available polar stationary phases.

McLean, Michael M.

145

Comparing nanostructured hydroxyapatite coating on AZ91 alloy samples via sol-gel and electrophoretic deposition for biomedical applications.  

PubMed

Magnesium is one of the most critical elements in hard tissues regeneration and therefore causes speeding up the restoration of harmed bones, while high deterioration rate of magnesium in body fluid restricts it to be used as biodegradable implants. Alloying magnesium with some relatively nobler metals such as aluminium, zinc, rare earth elements, magnesium-bioceramics composites, and surface modification techniques are some of the routes to control magnesium corrosion rate. In this study AZ91 magnesium alloy had been coated by nanostructured hydroxyapatite via sol-gel dip coating and electrophoretical methods to survey the final barricade properties of the obtained coatings. In order to perform electrophoretic coating, powders were prepared by sol-gel method, and then the powders deposited on substrates utilizing direct current electricity. Zeta potentials of the electrophoresis suspensions were measured to determine a best mode for good quality coatings. Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) were used to confirm nanoscale dimension, and the uniformity of the nanostructured hydroxyapatite coating, respectively. Fourier Transform-Infrared and X-ray diffraction analysis were utilized for functional group and phase structure evaluation of the prepared coatings, correspondingly. Electrochemical corrosion tests were performed in SBF at 37±1 (°)C which revealed considerable increase in corrosion protection resistivity and corrosion current density for electrophoretic coated specimens versus sol-gel coated specimens. Results showed that both sol-gel and electrophoretical techniques seem to be suitable to coat magnesium alloys for biomedical applications but electrophoretic coating technique is a better choice due to the more homogeneity and more crystalline structure of the coating. PMID:25095258

Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

2014-12-01

146

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

147

Humidity dependencies of porous sol-gel and silica glass linear sizes  

Microsoft Academic Search

Measurements of the porous sol-gel and porous silica glass linear size dependencies on humidity of the surrounding atmosphere were performed using the interferometric techniques. The secondary silica gel existing in the voids of silica porous glasses is absent in the sol-gel glasses. The pore size distribu- tions have two peaks for the sol-gel glass while there are several peaks with

S. A. GEVELUYK; I. K. DOYCHO; L. P. PROKOPOVICH; E. RYSIAKIEWICZ-PASEK; E. D. SAFRONSKY

148

Hybrid organic-inorganic sol-gel materials and components for integrated optoelectronics  

NASA Astrophysics Data System (ADS)

On the technical platform of hybrid organic-inorganic sol-gel, the integrated optoelectronics in the forms of heterogeneous integration between the hybrid sol-gel waveguide and the high refractive index semiconductors and the nonlinear functional doping of disperse red chromophore into hybrid sol-gel is developed. The structure of hybrid sol-gel waveguide on high index semiconductor substrate is designed with BPM-CAD software. A hybrid sol-gel based on MAPTMS and TEOS suitable for lower cladding for the waveguide is developed. The multi-layer hybrid sol-gel waveguide with good mode confinement and low polarization dependence is fabricated on Si and InP. As proof of concept, a 1 x 12 beam splitter based on multimode interference is fabricated on silicon substrate. The device shows excess loss below 0.65 dB and imbalance below 0.28 dB for both TE and TM polarization. A nonlinear active hybrid sol-gel doped with disperse red 13 has been developed by simple co-solvent method. It permits high loading concentration and has low optical loss at 1550 nm. The second-order nonlinear property of the active sol-gel is induced with corona poling and studied with second harmonic generation. A 3-fold of enhancement in the poling efficiency is achieved by blue light assisted corona poling. The chromophore alignment stability is improved by reducing the free volume of the formed inorganic network from the sol-gel condensation reaction. An active sol-gel channel waveguide has been fabricated using active and passive hybrid sol-gel materials by only photopatterning and spin-coating. An amplitude modulator based on the active sol-gel containing 30 wt.% of DR13 shows an electro-optic coefficient of 14 pm/V at 1550 nm and stable operation within the observation time of 24 days.

Lu, Dong

149

Examination of the structure of sol–gel derived matrices for optoelectronic sensors  

Microsoft Academic Search

Sol–gel technology was used to produce glass-like materials doped with different compounds. The sol–gel matrices were prepared on the way of acid hydrolysis. Two types of materials in the form of thin layers were examined: sol–gel bulk type (type I) and thin film type (type II). The structure was visualized by means of a light microscope. The microscopic images were

Agnieszka Ulatowska; Halina Podbielska; Monika Lechna; Bronis?aw Grzegorzewski

2001-01-01

150

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

151

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.

2014-06-01

152

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

153

Sol–gel synthesis and electrical characterization of (Pb, Ca)TiO 3 thin films  

Microsoft Academic Search

Calcium modified lead titanate films have been prepared on Pt\\/Ti\\/SiO2\\/Si substrates using a sol–gel route. The sols were prepared from propanediol solutions of Pb(CH3COO)2xH2O, Ti(OC3H7)2(CH3COCHCOCH3)2 and Ca(NO3)2xH2O. Tetragonal phase (Pb, Ca)TiO3 films could be produced by firing the coatings at 650C for 30 min. The limiting thickness\\u000a of crack-free single layers was ?0.4 ?m, but 3 ?m thick films could

S. CHEWASATN; S. J MILNE

1997-01-01

154

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

NASA Astrophysics Data System (ADS)

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. MgF2 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 MgF2 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.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. MgF2 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 MgF2 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. Electronic supplementary information (ESI) available: See DOI: 10.1039/c1nr10843c

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

2011-11-01

155

Durable hydrophobic sol-gel finishing for textiles  

NASA Astrophysics Data System (ADS)

The surface of cotton textile was modified to create a water-repellent finishing by depositing a modifying coatings using the sol-gel technique. Treated textiles evaluated using scanning electron microscopy, X-Ray powder diffraction (XRD). The wettability of treated fabrics was characterized by water contact angle and drop test. The results showed that the cotton textile treated with 7.5 wt.% zinc acetate dihydrate sol showed excellent hydrophobic properties, water contact angle could reach 145°C without decreasing after 50 hydrothermal treatment cycles.

Vihodceva, S.; Kukle, S.; Bitenieks, J.

2015-03-01

156

Sol Gel-Derived SBA-16 Mesoporous Material  

PubMed Central

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

Rivera-Muñoz, Eric M.; Huirache-Acuña, Rafael

2010-01-01

157

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

SciTech Connect

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

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

1999-04-05

158

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

NASA Astrophysics Data System (ADS)

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

Barhoum, Moussa

159

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

160

Synthesis and characterization of sol–gel derived PVA-titanium dioxide (TiO 2 ) nanocomposite  

Microsoft Academic Search

Novel PVA\\/TiO2 polymer nanocomposites have been prepared at low temperature via sol–gel route. XRD analysis showed the particles to be elongated\\u000a along a- and b-direction but contracted along c-direction. PVA-assisted TiO2 nanocomposite samples dried at a temperature of 35 °C were found to have ~12 nm particle size. It was found that the composite\\u000a nanoparticles had an increased degree of crystallinity in

Archana Maurya; Pratima Chauhan

161

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

SciTech Connect

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

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

2005-09-01

162

Sol-gel derived ceramic electrolyte films on porous substrates  

SciTech Connect

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

Kueper, T.W.

1992-05-01

163

Practical protocols for lipase immobilization via sol-gel techniques.  

PubMed

Lipases can be efficiently entrapped in the pores of hydrophobic silicates by a simple and cheap sol-gel process in which a mixture of a hydrophobic alkylsilane RSi(OCH3)3 and Si(OCH3)4 is hydrolyzed under basic conditions in the presence of the enzyme. Additives such as isopropanol, polyvinyl alcohol, cyclodextrins, ionic liquids or surfactants enhance the efficiency of this type of lipase-immobilization. The main area of application of these heterogeneous biocatalysts concerns esterification or transesterification in organic solvents, ionic liquids, or supercritical carbon dioxide. Rate enhancements (relative to the traditional use of lipase powders) of several orders of magnitude have been observed, in addition to higher thermal stability. The lipase-immobilizates are particularly useful in the kinetic resolution of chiral esters, enantioselectivity often being higher than what is observed when using the commercial forms of these lipases (powder or classical immobilizates). Thus, due to the low price of sol-gel entrapment, the excellent performance of the lipase-immobilizates, and the ready recyclability, the method is industrially viable. PMID:23934809

Reetz, Manfred T

2013-01-01

164

Nanospherical silica as luminescent markers obtained by sol-gel.  

PubMed

Hybrid nanosilicas constitute a broad study field. They find application as catalysts, pigments, drug delivery systems, and biomaterials, among others, and it is possible to obtain them via the sol-gel methodology. Lanthanide ions present special properties like light emission. Their incorporation into a silica matrix can enhance their luminescent properties, which enables their application as luminescent markers. This work reports on (i) the preparation of luminescent spherical hybrid silica nanoparticles by the hydrolytic sol-gel methodology, (ii) doping of the resulting matrix with the europium(III) ion or its complex with 1,10-phenanthroline, and (iii) characterization of the final powders by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and europium(III) ion photoluminescence. The synthesized materials consisted of hybrid, amorphous, polydispersed nonspherical silicas with average size of 180 nm. Photoluminescence confirmed incorporation of the europium(III) ion and its complex into the silica matrix-the ligand-metal charge transfer band emerged in the excitation spectra. The emission spectra presented the bands corresponding to the transition of the excited state (5)D0 level to (7)FJ (J = 0, 1, 2, 3 and 4). The main emission occurred in the red region; the lifetime was long. These characteristics indicated that the prepared nanospherical hybrid silicas could act as luminescent markers. PMID:25686772

Azevedo, Caroline B; Batista, TúlioM; de Faria, Emerson H; Rocha, Lucas A; Ciuffi, Katia J; Nassar, Eduardo J

2015-03-01

165

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

NASA Astrophysics Data System (ADS)

Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time. The test systems and experimental results obtained will be presented. 1. Okubo, T., Tsuchida, A., Okuda, T., Fujitsuna, K., Ishikawa, M., Morita, T., Tada, T. , Kinetic Analyses of Colloidal Crystallization in Microgravity -Aircraft Experiments. . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999. 153: p. 515-524. 2. Okubo, T., Tsuchida, A., Kobayashi, K., Kuno, A., Morita, T., Fujishima, M., Kohno, Y., Kinetic Study of the Formation Reaction of Colloidal Silica Spheres in Microgravity Using Aircraft. Colloid Polymer Science, 1999. 277(5): p. 474-478. 3. Pienaar, C.L., Chiffoleau, G. J. A., Follens, L. R. A., Martens, J. A., Kirschhock, C. E. A., Steinberg, T. A., Effect of Gravity on the Gelation of Silica Sols. Chem. Mater., 2007. 19(4): p. 660-664. 4. Smith, D.D., et al., Effect of Microgravity on the Growth of Silica Nanostructures. Langmuir, 2000. 16(26): p. 10055-10060. 5. Zhang, X., Johnson, D.P., Manerbino, A.R., Moore, J.J., Schowengerdt, F. , Recent Mi-crogravity Results in the Synthesis of Porous Materials. AIP Conference Proceedings (Space Technology and Applications International Forum-1999, Pt. 1), 1999. 458: p. 88-93. 6. Dunbar, P.B., Bendzko, N.J.,, 1H and 13C NMR observation of the reaction of acetic acid with titanium isopropoxide. Materials Chemistry and Physics, 1999. 59: p. 26-35. 7. Krunks, M., Oja, I., T˜nsuaadu, K., Es-Souni, M., Gruselle, M., Niinistü,. L, Thermoanalytical study of acetylacetonate-modified titanium (iv) isopropoxide as precursor for TiO2 films. Journal of Thermal Analysis and Calorimetry, 2005: p. 483-488. 8. Moran, P.D., Bowmaker, G. A., Cooney, R. P., Vibrational Spectra and Molecular Associa-tion of Titanium Tetraisopropoxide. Inorg. Chem., 1998. 37(1): p. 2741-2748. 9. Somogyvari, A., Serpone, N.,, Evidence for five-coordination in titanium(1V) complexes. A nuclear magnetic resonance investigation. Canadian Journal of Chemistry, 1977. 56: p. 316-319.

Hales, Matthew; Martens, Wayde; Steinberg, Theodore

166

Electrospun sol-gel fibers for fluorescence-based sensing  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

167

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

PubMed

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

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

2014-08-01

168

Scintillation of Sol-Gel derived Lutetium orthophosphate doped with rare earth ions.  

E-print Network

1 Scintillation of Sol-Gel derived Lutetium orthophosphate doped with rare earth ions. C. Mansuy1. Because of the required high density, lutetium based oxides materials are very interesting candidates Section Materials preparation Sol-Gel derived samples In a first step, a mixture of Lutetium and Ln

Paris-Sud XI, Université de

169

Hydroxy and fluorapatite films on Ti alloy substrates: Sol-gel preparation and characterization  

Microsoft Academic Search

In this paper we describe the preparation of hydroxyfluorapatite (HFA) and fluorapatite (FA) films deposited on titanium alloys by means of the dip-coating method starting from a sol-gel prepared colloidal solution. These materials are compared with hydroxyapatite (HA) films prepared via sol gel and commercial films prepared by means of plasma spray. The film characterization from the point of view

M. Cavalli; G. Gnappi; A. Montenero; D. Bersani; P. P. Lottici; S. Kaciulis; G. Mattogno; M. Fini

2001-01-01

170

Chemical sensing using sol-gel derived planar waveguides and indicator phases  

Microsoft Academic Search

A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW).

Lin. Yang; S. Scott. Saavedra

1995-01-01

171

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

172

Aqueous Sol-Gel Process for Protein Encapsulation Rimple B. Bhatia and C. Jeffrey Brinker*,,  

E-print Network

enzyme-doped silica monoliths and to investigate the effect of silica as host matrix on enzyme kinetics and diffusional effects in the pores of the sol-gel matrix. The encapsulated enzymes also exhibited a different p Manuscript Received June 10, 2000 Porous silica materials made by low-temperature sol-gel process

Singh, Anup

173

Sol-Gel Precursors for Ceramics from Minerals Simulating Soils from the Moon and Mars  

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 some preliminary 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 A12O3 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 simulant soils. Clear sol-gel precursors have been obtained by dissolution of silica from Lunar simulant soil in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Thermogravimetric Analysis and X-ray Photoelectron Spectroscopy were used to characterize the elemental composition and structure of the precursor molecules. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors. In the second set of experiments, we used the same starting materials to synthesize silicate esters in acidified alcohol mixtures. Preliminary results indicate the presence of silicon alkoxides in the product of distillation.

Sibille, Laurent; Gavira-Gallardo, Jose-Antonio; Hourlier-Bahloul, Djamila

2003-01-01

174

Optical fiber sensor having a sol-gel fiber core and a method of making  

DOEpatents

A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

2006-06-06

175

Passive and active sol-gel integrated optics for heterogeneous integration  

NASA Astrophysics Data System (ADS)

The advantage of hybrid organic-inorganic sol-gel as a simple, low-cost method for the fabrication of optoelectronic integration is described. High performance integrated optics using mulit-layer photo-patternable hybrid sol-gel on high-index InP compound semiconductor is achieved. An MMI based 1x12 beam splitter with low polarization sensitivity and high uniformity is demonstrated. The development of EO and NLO active sol-gels are described and the fabrication of active waveguides are presented. The chromophore doped active sol-gels demonstrate high stability which makes them attractive material for integrated optoelectronics. The results show the great potential of the hybrid sol-gel for heterogeneous integration with semiconductor lasers and optoelectronic components.

Fallahi, Mahmoud

2004-08-01

176

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

177

Applications of iron (III) nitrate to obtain the multiferroic Pb(Fe 1\\/2Nb 1\\/2)O 3 ceramics by the sol–gel method  

Microsoft Academic Search

In the present work the results of preparation of the multiferroic Pb(Fe1\\/2Nb1\\/2)O3 (PFN) ceramics were presented. A synthesis of the PFN ceramics powders was carried out via a wet chemical route, by the sol–gel method. The densification process of ceramic powders was made by using the free sintering method (a conventional sintering) or by the hot uniaxial pressing method.Measurements of

D. Bochenek; Z. Surowiak

2009-01-01

178

Nanostructure magneto-optical thin films of rare earth (RE=Gd,Tb,Dy) doped cobalt spinel by sol-gel synthesis  

Microsoft Academic Search

Nanocrystalline CoFe1.9RE0.1O4 [rare earth (RE=Gd,Tb,Dy)] films have been prepared by the sol-gel route, and their polar magneto-optical (MO) Kerr rotation and ellipticity have been determined in the spectral range of 4000-8000 Å. The films are composed of nanometer grains with the spinel structure. RE doped cobalt spinel ferrites are found to have dramatic changes in magnetic and MO properties, with

Fuxiang Cheng; Chunsheng Liao; Junfeng Kuang; Zhigang Xu; Chunhua Yan; Liangyao Chen; Haibin Zhao; Zhu Liu

1999-01-01

179

Microstructure, optical and optoelectrical properties of mesoporous nc-TiO 2 films by hydrolysis-limited sol–gel process with different inhibitors  

Microsoft Academic Search

Mesoporous nanocrystalline titania (nc-TiO2) films were synthesized by sol–gel route using poly (alkylene oxide) block copolymer as template and tetrabutyl orthotitanate as titanium source. Influence of acetylacetone (AcAc), glacial acetic acid, HCl and AcAc-HCl as inhibitors on hydrolysis\\/condensation reaction was investigated. The mesopore structure, crystalline phase and optical characteristics were analyzed by N2 adsorption, X-ray diffraction, transmission electron microscopy and

Yanan Fu; Zhengguo Jin; Yong Ni; Haiyan Du; Tao Wang

2009-01-01

180

Synthesis of indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) nano-powder by sol–gel combustion hybrid method  

Microsoft Academic Search

ITO and FTO nano-powders were synthesized employing a new route sol–gel combustion hybrid method using acetylene black as a fuel. The dried gels exhibited an auto-catalytic combustion behavior. ITO and FTO nano-powders with narrow size distribution were obtained at 750 °C. Crystal structures were examined by powder X-ray diffraction (XRD) and particle morphology as well as crystal size was investigated by

Chi-Hwan Han; Sang-Do Han; Jihye Gwak; S. P. Khatkar

2007-01-01

181

Magnetic properties of As2O3- and Sb2O3-doped BaM hexagonal ferrites prepared by the sol-gel method  

Microsoft Academic Search

Ba-M hexagonal ferrites with As2O3 and Sb2O3 doping have been prepared in the composition series BaO.(6 - x)Fe2O3 .xM2O3 (M = As or Sb) with 0 <= x <= 0.4 by the sol-gel route. The precursor sol is prepared by using barium acetate and the chlorides of iron and arsenic\\/antimony respectively. Pellitized powders of these hexaferrites are sintered in the

P. Brahma; Anit K. Giri; D. Chakravorty; M. Roy; D. Bahadur

1992-01-01

182

Structural and Physical Properties of La 2\\/3 Ca 1\\/3 MnO 3 Prepared via a Modified Sol-Gel Method  

Microsoft Academic Search

High purity powder of manganese perovskite, La2\\/3Ca1\\/3MnO3, is prepared using a modified sol-gel synthesis based on the dissolution and homogenisation of metal salts in ethanol-acetic acid mixture without using any complexing aid (e.g., polyol or polyhydroxy acid, etc.), which is essentially used in the polymeric precursor routes. This modification minimises the organic contamination in the resulting ceramic that is formed

S. Mathur; H. Shen

2002-01-01

183

Sol-gel processing of silica supported Ni and Co molybdate catalysts used for isoC 4 alkane oxidative dehydrogenation  

Microsoft Academic Search

A novel sol-gel route has been developed to prepare silica supported Ni and Co molybdate catalysts. The metal oxides obtained are homogeneously dispersed in the silica matrix and specifically for NiMoO4 the high-temperature ?-phase which is catalytically more active has been found to be stable at room temperature. The catalytic activities of the silica supported stoichiometric Ni and Co molybdates

E. Tempesti; A. Kaddouri; C. Mazzocchia

1998-01-01

184

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

185

Sol-gel synthesis and characterization of mesoporous manganese oxide  

SciTech Connect

Mesoporous manganese oxide (MPMO) from reduction of KMnO{sub 4} with maleic acid, was obtained and characterized in detail. The characterization of the material was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray powder diffractometry (XRD) and N{sub 2} sorptometry. The results showed that MPMO is a pseudo-crystalline material with complex network pore structure, of which BET specific surface area is 297 m{sup 2}/g and pore size distribution is approximately in the range of 0.7-6.0 nm. The MPMO material turns to cryptomelane when the calcinating temperature rises to 400 deg. C. The optimum sol-gel reaction conditions are KMnO{sub 4}/C{sub 4}H{sub 4}O{sub 4} molar ratio=3, pH=7 and gelation time>6 h.

Hong Xinlin; Zhang Gaoyong; Zhu Yinyan; Yang Hengquan

2003-10-30

186

Statistical Thermodynamics of Irreversible Aggregation: The Sol-Gel Transition  

PubMed Central

Binary aggregation is known to lead, under certain kinetic rules, to the coexistence of two populations, one consisting of finite-size clusters (sol), and one that contains a single cluster that carries a finite fraction of the total mass (giant component or gel). The sol-gel transition is commonly discussed as a phase transition by qualitative analogy to vapor condensation. Here we show that the connection to thermodynamic phase transition is rigorous. We develop the statistical thermodynamics of irreversible binary aggregation in discrete finite systems, obtain the partition function for arbitrary kernel, and show that the emergence of the gel cluster has all the hallmarks of a phase transition, including an unstable van der Waals loop. We demonstrate the theory by presenting the complete pre- and post-gel solution for aggregation with the product kernel. PMID:25748055

Matsoukas, Themis

2015-01-01

187

Statistical Thermodynamics of Irreversible Aggregation: The Sol-Gel Transition  

NASA Astrophysics Data System (ADS)

Binary aggregation is known to lead, under certain kinetic rules, to the coexistence of two populations, one consisting of finite-size clusters (sol), and one that contains a single cluster that carries a finite fraction of the total mass (giant component or gel). The sol-gel transition is commonly discussed as a phase transition by qualitative analogy to vapor condensation. Here we show that the connection to thermodynamic phase transition is rigorous. We develop the statistical thermodynamics of irreversible binary aggregation in discrete finite systems, obtain the partition function for arbitrary kernel, and show that the emergence of the gel cluster has all the hallmarks of a phase transition, including an unstable van der Waals loop. We demonstrate the theory by presenting the complete pre- and post-gel solution for aggregation with the product kernel.

Matsoukas, Themis

2015-03-01

188

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

189

Sol-Gel processing of silica nanoparticles and their applications.  

PubMed

Recently, silica nanoparticles (SNPs) have drawn widespread attention due to their applications in many emerging areas because of their tailorable morphology. During the last decade, remarkable efforts have been made on the investigations for novel processing methodologies to prepare SNPs, resulting in better control of the size, shape, porosity and significant improvements in the physio-chemical properties. A number of techniques available for preparing SNPs namely, flame spray pyrolysis, chemical vapour deposition, micro-emulsion, ball milling, sol-gel etc. have resulted, a number of publications. Among these, preparation by sol-gel has been the focus of research as the synthesis is straightforward, scalable and controllable. Therefore, this review focuses on the recent progress in the field of synthesis of SNPs exhibiting ordered mesoporous structure, their distribution pattern, morphological attributes and applications. The mesoporous silica nanoparticles (MSNPs) with good dispersion, varying morphology, narrow size distribution and homogeneous porous structure have been successfully prepared using organic and inorganic templates. The soft template assisted synthesis using surfactants for obtaining desirable shapes, pores, morphology and mechanisms proposed has been reviewed. Apart from single template, double and mixed surfactants, electrolytes, polymers etc. as templates have also been intensively discussed. The influence of reaction conditions such as temperature, pH, concentration of reagents, drying techniques, solvents, precursor, aging time etc. have also been deliberated. These MSNPs are suitable for a variety of applications viz., in the drug delivery systems, high performance liquid chromatography (HPLC), biosensors, cosmetics as well as construction materials. The applications of these SNPs have also been briefly summarized. PMID:25466691

Singh, Lok P; Bhattacharyya, Sriman K; Kumar, Rahul; Mishra, Geetika; Sharma, Usha; Singh, Garima; Ahalawat, Saurabh

2014-11-01

190

Sol-Gel Glass Holographic Light-Shaping Diffusers  

NASA Technical Reports Server (NTRS)

Holographic glass light-shaping diffusers (GLSDs) are optical components for use in special-purpose illumination systems (see figure). When properly positioned with respect to lamps and areas to be illuminated, holographic GLSDs efficiently channel light from the lamps onto specified areas with specified distributions of illumination for example, uniform or nearly uniform irradiance can be concentrated with intensity confined to a peak a few degrees wide about normal incidence, over a circular or elliptical area. Holographic light diffusers were developed during the 1990s. The development of the present holographic GLSDs extends the prior development to incorporate sol-gel optical glass. To fabricate a holographic GLSD, one records a hologram on a sol-gel silica film formulated specially for this purpose. The hologram is a quasi-random, micro-sculpted pattern of smoothly varying changes in the index of refraction of the glass. The structures in this pattern act as an array of numerous miniature lenses that refract light passing through the GLSD, such that the transmitted light beam exhibits a precisely tailored energy distribution. In comparison with other light diffusers, holographic GLSDs function with remarkably high efficiency: they typically transmit 90 percent or more of the incident lamp light onto the designated areas. In addition, they can withstand temperatures in excess of 1,000 C. These characteristics make holographic GLSDs attractive for use in diverse lighting applications that involve high temperatures and/or requirements for high transmission efficiency for ultraviolet, visible, and near-infrared light. Examples include projectors, automobile headlights, aircraft landing lights, high-power laser illuminators, and industrial and scientific illuminators.

Yu, Kevin; Lee, Kang; Savant, Gajendra; Yin, Khin Swe (Lillian)

2005-01-01

191

The growth and characterization of L-arginine phosphate microcrystals in a silica sol gel matrix  

NASA Astrophysics Data System (ADS)

Silica sol-gel has proven to be a versatile material that can host a number of inorganic and organic dopant molecules, providing an environment in which they may retain their activity. This dissertation studies the relationship between crystallization and gelation in a system consisting of L-arginine phosphate (LAP), an organic non-linear optical crystal, in an inorganic silica sol-gel matrix. The objectives of this research are to investigate the mechanisms of crystal nucleation and growth in a silica sol-gel matrix. Complex impedance measurements were used to determine the solubility of LAP in sol-gel as a function of temperature, the induction times for crystallization of LAP, and the overall rate of LAP precipitation. Analysis of the induction times was performed to determine the interfacial energies, surface entropy factors, and nucleation and growth mechanisms of LAP in sol-gel over a range of temperatures and concentrations. Nucleation and growth of LAP in sol-gel was found to follow a model of primary nucleation followed by spiral growth (5°C to 20°C) or normal growth (25°C to 40°C) for LAP concentrations high enough that nucleation occurs in the sol. For lower LAP concentrations, heterogeneous nucleation occurs on sample interfaces or electrodes. The solubility of LAP in silica sol-gel was found to follow an Arrhenius relationship, with an enthalpy of solution of 0.68 eV. The enthalpy of solution for LAP in sol-gel is comparable to that in aqueous solutions, while the pre-exponential factor is about 8 times smaller in sol-gel than in water. The interfacial energies of LAP in sol-gel are close to, but slightly larger than, those in aqueous solution. The interfacial energies decrease with increasing temperature at about the same rate in sol-gel as in aqueous solution. Conductivity of LAP in sol-gel is primarily through proton conduction and follows an Arrhenius relationship with an activation energy for conduction of 0.26 eV and a pre-exponential factor that depends upon the square root of the LAP concentration.

Faltens, Tanya Anne

192

Elaboration and characterization of sol-gel derived ZrO2 thin films treated with hot water  

NASA Astrophysics Data System (ADS)

We describe the preparation and characterization of zirconia (ZrO2) thin films via sol-gel route by spin-coating method. By utilizing alkoxide s Zr[O(CH2)3CH3]4 in the presence of ethanol (EtOH), nitric acid and acetylacetone as a chelating agent, a stable sol of ZrO2 was obtained. Smooth surface morphology with nano-cracks was exhibited for all ZrO2 thin films being fabricated. The film thickness varied from 39 to 206 nm depending on the molar ratio of EtOH during the sol preparation and also annealing temperature applied. All ZrO2 films possess high optical transmittance. Refractive index of the thin film was ranging from 1.6 to 2.4 depending on molar ratio of EtOH and annealing temperature. Tetragonal phase of ZrO2 was formed after annealed at 400 °C. Crystallinity of ZrO2 was enhanced by increasing molar ratio of EtOH. Crystallite size of tetragonal ZrO2 was ranged from 3.0 to 9.9 nm. A hot-water treatment reduced the film thickness and further improved crystallinity of the sol-gel derived oxide.

Soo, Mun Teng; Prastomo, Niki; Matsuda, Atsunori; Kawamura, Go; Muto, Hiroyuki; Noor, Ahmad Fauzi Mohd; Lockman, Zainovia; Cheong, Kuan Yew

2012-04-01

193

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. PMID:23798771

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

2013-01-01

194

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

E-print Network

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

Chan, Yinthai

2006-01-01

195

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

196

Formation of LaF 3 microcrystals in sol–gel silica  

Microsoft Academic Search

A novel sol–gel process for silica\\/fluoride composites is described. Crystallization of LaF3 in the sol–gel silica has been investigated. Dry silica gels containing La3+ and trifluoroacetate ions (CF3COO?) were produced from tetramethylorthosilicate (TMOS), methanol, dimethylformamide, lanthanum acetate, trifluoroacetic acid, water and nitric acid. By heating the gels at temperatures above 300°C, LaF3 microcrystals with a size of 10–30 nm were

Shinobu Fujihara; Chizuko Mochizuki; Toshio Kimura

1999-01-01

197

High temperature sol–gel insulation coatings for HTS magnets and their adhesion properties  

Microsoft Academic Search

This paper describes the adhesion properties of sol–gel insulation coatings with silver tape substrates using a mini-tensile-testing for HTS magnets. The sol–gel coatings were produced using solutions of Zr, Mg, Y, Ce, In and Sn based organometallic compounds. The growth mechanism of these coatings on Ag and AgMg sheathed Bi-2212 superconducting tapes was characterized by scanning electron microscopy, energy dispersive

E. Celik; E. Avci; Y. S. Hascicek

2000-01-01

198

Sol–gel immobilized room-temperature phosphorescent metal-chelate as luminescent oxygen sensing material  

Microsoft Academic Search

The chelate formed by 8-hydroxy-7-iodo-5-quinolinesulfonic acid (ferron) with aluminium exhibits strong room-temperature phosphorescence (RTP) when retained on a solid support. In a previous paper we have found that sol–gel technology is a very useful approach for developing RTP optical sensors as a new way to immobilize lumiphors. Sol–gel active phases proved to exhibit a high physical rigidity that enhanced relative

J. M Costa-Fernández; M. E Diaz-Garc??a; A Sanz-Medel

1998-01-01

199

Preparation of Gd 2 CuO 4 via sol-gel in microemulsions  

Microsoft Academic Search

We have synthesized microparticles of Gd2CuO4 via sol-gel technology in microemulsions, carrying out the sol-gel process inside the microdroplets of the microemulsion.\\u000a The microemulsion was a mixture of cyclohexane\\/brij 96\\/aqueous phase (70:20:10% weight). Urea was used as gelificant agent.\\u000a The method is based on removing solvents from the mixture applying vacuum in order to obtain a gel when cooling down.

C. Vázquez-Vázquez; J. Mahía; M. López-Quintela; J. Mira; J. Rivas

200

Preparation and Characterization of Sol-Gel TiO2\\/ITO Photoelectrodes  

Microsoft Academic Search

In this work, nanocrystalline TiO2\\/ITO electrodes were prepared by sol-gel method starting from tetrabutyl orthotitanate (Ti(OBun)4) reacted with hydrogen peroxide in the ice-water bath. The sol-gel derived TiO2 films were characterized by XRD, SEM, BET, and UV\\/Vis absorption spectroscopic techniques. The preparation conditions, including the number of coats and calcination temperature, were also investigated. Furthermore, PEC cells were constructed for

Chia-Hung Liang; Hung-Yi Chang; Tsz-Wei Liou; Huey-Ing Chen

2008-01-01

201

PREPARATION AND CHARACTERIZATION OF SOL–GEL-DERIVED TiO2\\/ITO PHOTOELECTRODES  

Microsoft Academic Search

In this work, nanocrystalline TiO2\\/ITO electrodes were prepared by sol–gel method starting from tetrabutyl orthotitanate (Ti(OBun)4) reacted with hydrogen peroxide in the ice-water bath. The sol–gel derived TiO2 films were characterized by XRD, SEM, BET, and UV\\/Vis absorption spectroscopic techniques. The preparation conditions, including the number of coats and calcination temperature, were also investigated. Furthermore, PEC cells were constructed for

CHIA-HUNG LIANG; HUNG-YI CHANG; TSZ-WEI LIOU; HUEY-ING CHEN

2008-01-01

202

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

203

Characterization of titanium alkoxide sol–gel systems designed for anti-icing coatings: I. Chemistry  

Microsoft Academic Search

Recent interest in sol–gel chemistry involving titanium alkoxide precursors has been prompted by the ability to control the\\u000a morphology of the final TiO2 structure. The ligands used in these processes are typically sacrificial and are removed once the process is complete. In\\u000a contrast, the sol–gel chemistry presented here is used to facilitate the slow release of the attached alkoxide ligands:

Jennifer Ayres; W. H. Simendinger; C. M. Balik

2007-01-01

204

Functionalization of ceramic tile surface by sol-gel technique.  

PubMed

The aim of this investigation was the surface functionalization of industrial ceramic tiles by sol-gel technique to improve at the same time the cleanability of unglazed surfaces. This objective was pursued through the design and preparation of nanostructured coating that was deposited on polished unglazed tiles by air-brushing. In particular TiO(2)-SiO(2) binary film with 1, 2 or 5wt% of titania were prepared by using tetraethoxysilane and titania nanoparticles as precursors. The obtained films were characterized by scratch tests to verify the adhesion of the coatings to the polished tiles. To mainly evaluate the effect of the thermal treatment (temperature range 100-600 degrees C) on the photocatalicity of the coatings, the films were studied under UV exposure by contact angle measurements and cleanability test. Particular attention has been paid to preserve the aesthetical aspect of the final product and the obtained hue variation was evaluated by means of UV-visible spectroscopy and colorimetric analysis. PMID:19398103

Bondioli, F; Taurino, R; Ferrari, A M

2009-06-15

205

Processing, properties, and applications of sol-gel silica optics  

NASA Astrophysics Data System (ADS)

For many years the market share maintained by U.S. optics manufacturers has been declining continuously caused in part by intense competition principally from countries in the Far East, and in part by the lack of a highly trained cadre of opticians to replace the current generation. This fact could place in jeopardy the defense system of the United States in case of international war. For example, in 1987, optical glass component imports accounted for approximately 50 percent of the Department of Defense (DOD) consumption. GELTECH's sol-gel technology is a new process for making a high quality optical glass and components for commercial and military uses. This technology offers in addition to being a local source of optics, the possibility to create new materials for high-tech optical applications, and the elimination of the major part of grinding and polishing for which the skill moved off-shore. This paper presents a summary of the solgel technology for the manufacture of high quality optical glass and components. Properties of pure silica glass made by solgel process (Type V and Type VI silicas) are given and include: ultraviolet, visible and near infrared spectrophotometry, optical homogeneity and thermal expansion. Many applications such as near net shape casting or Fresnel lens surface replication are discussed. Several potential new applications offered by the solgel technology such as organic-inorganic composites for non linear optics or scintillation detection are also reported in this paper.

Nogues, Jean-Luc R.; LaPaglia, Anthony J.

1989-12-01

206

Hybrid silica-PVA nanofibers via sol-gel electrospinning.  

PubMed

We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies. PMID:22394080

Pirzada, Tahira; Arvidson, Sara A; Saquing, Carl D; Shah, S Sakhawat; Khan, Saad A

2012-04-01

207

Hybrid carbon silica nanofibers through sol-gel electrospinning.  

PubMed

A controlled sol-gel synthesis incorporated with electrospinning is employed to produce polyacrylonitrile-silica (PAN-silica) fibers. Hybrid fibers are obtained with varying amounts of silica precursor (TEOS in DMF catalyzed by HCl) and PAN. Solution viscosity, conductivity, and surface tension are found to relate strongly to the electrospinnability of PAN-silica solutions. TGA and DSC analyses of the hybrids indicate strong intermolecular interactions, possibly between the -OH group of silica and -CN of PAN. Thermal stabilization of the hybrids at 280 °C followed by carbonization at 800 °C transforms fibers to carbon-silica hybrid nanofibers with smooth morphology and diameter ranging from 400 to 700 nm. FTIR analysis of the fibers confirms the presence of silica in the as-spun as well as the carbonized material, where the extent of carbonization is also estimated by confirming the presence of -C?C and -C?O peaks in the carbonized hybrids. The graphitic character of the carbon-silica fibers is confirmed through Raman studies, and the role of silica in the disorder of the carbon structure is discussed. PMID:25474752

Pirzada, Tahira; Arvidson, Sara A; Saquing, Carl D; Shah, S Sakhawat; Khan, Saad A

2014-12-30

208

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

209

Control of rehydration in sol-gel glasses  

NASA Astrophysics Data System (ADS)

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

Ortiz, Carlos; Boye, Daniel

2007-11-01

210

/dopamine films prepared by sol-gel method  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

211

Optical properties of sol-gel-derived PZT thin films  

NASA Astrophysics Data System (ADS)

A series of sol-gel derived PT-based films, including PT, PZ, PZT, PLT, PLZ and PLZT, was prepared on platinized Si, fused SiO2 and Corning 7059 substrates. These films were fired at 400 - 700 C for 30 mins. The phase assembly and development were dependent on the precursor chemistries, processing and choice of substrates. The presence of Zr impacted significantly on the crystallization behavior, PbO loss and cracking behavior of the films. Crystallization was severely retarded, especially in Zr-containing PZT films when deposited on amorphous substrates compared to crystalline Pt substrates. Amorphous and crystalline PZT films can be utilized for passive and active optical applications. Waveguiding was achieved in an amorphous PZT 53/47 and a crystalline PLT 28 films and gave attenuation losses of 1.0 and 1.4 dB/cm respectively which represent the lowest values reported to date. The optical properties of the films were investigated using ellipsometry, UV-VIS transmission spectroscopy and waveguide loss measurements. Depending on composition and processing conditions, PZT films (2500 A thick) with refractive indices of 1.60 to 2.33 and absorption edges of 2900 - 3100 A can be obtained. It was ascertained that the resulting interfacial reaction layers between the films and substrates affected considerably the optical properties of thinner films (< 2000 A).

Teowee, Gimtong T.; Boulton, J. M.; Motakef, Sharnaz; Uhlmann, Donald R.; Zelinski, Brian J.; Zanoni, Raymond; Moon, M.

1992-12-01

212

Sol-gel PZT and Mn-doped PZT thin films for pyroelectric applications  

NASA Astrophysics Data System (ADS)

Thin films of ferroelectric lead zirconate titanate (PbZr0.3Ti0.7O3 PZT30/70) and manganese-doped lead zirconate titanate ((Pb(Zr0.3Ti0.7)1- xMnx)O3, where x = 0.01, PM01ZT30/70; and x = 0.03, PM03ZT30/70) have been prepared using sol-gel processing techniques. These materials can be used as the pyroelectric thin films in uncooled infrared detectors. The thin films were prepared via a sol-gel route based on a hybrid solvent of methanol and ethanol with acetic acid, ethanolamine and ethylene glycol as additives. The final solution is non-moisture sensitive and stable. Films deposited on Pt/Ti/SiO2/Si substrates and annealed on a hot plate at 500-530 °C for a few minutes were seen to fully crystallize into the required perovskite phase and showed excellent ferroelectric behaviour, demonstrated by reproducible hysteresis loops (Pr = 33-37 µC cm-2, Ec( + ) = 70-100 kV cm-1, Ec(-) = -170 to -140 kV cm-1). The pyroelectric coefficient (p) was measured using the Byer-Roundy method. At 20 °C, p was 2.11×10-4 C m-2 K-1 for PZT30/70, 3.00×10-4 C m-2 K-1 for PM01ZT30/70 and 2.40×10-4 C m-2 K-1 for PM03ZT30/70 thin films. The detectivity figure-of-merit (FD) was 1.07×10-5 Pa-0.5 for PZT30/70, 3.07×10-5 Pa-0.5 for PM01ZT30/70 and 1.07×10-5 Pa-0.5 for PM03ZT30/70. These figures compare well with values reported previously.

Zhang, Q.; Whatmore, R. W.

2001-08-01

213

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

214

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

215

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

SciTech Connect

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

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

1997-12-01

216

Sol-gel synthesis of Fe-Co nanoparticles and magnetization study  

NASA Astrophysics Data System (ADS)

We report the synthesis of carbon encapsulated Fe-Co nanoparticles using conventional sol-gel route and its magnetization studies. The x-ray diffraction indicates the formation of the single phase body centered cubic alloy Fe-Co phase with cell parameter of 2.857 Å. Nanoparticles are highly crystalline and exhibit low index faceting as determined from high-resolution transmission electron microscopy (HRTEM) investigation. The observed orthogonal lattice planes with lattice distance of 2.86 Å are attributed to (100) and (010). HRTEM image confirms the cube like Fe-Co nanoparticles with core-shell structure of carbon encapsulation, composed of carbon and graphite materials. The magnetometry results of the carbon encapsulated alloy Fe-Co nanoparticles with core-shell structure designate as a ferromagnetically ordered soft magnet with coercive field of 890 Oe (at 5 K). The coercive field and magnetization value depend on the size of nanoparticles as well as the diamagnetic contribution of carbon encapsulation.

Nautiyal, Pranjal; Seikh, Md. Motin; Lebedev, Oleg I.; Kundu, Asish K.

2015-03-01

217

Development of electrochromic smart windows by sol-gel techniques  

NASA Astrophysics Data System (ADS)

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 layer or counter electrode. The adhesive properties of the electrolyte enabled the manufacture of electrochromic devices in a laminated structure: glassFTOWO3nanocomp.elect.CeO2-TiO2FTOglass. The conductivity of the nanocomposite electrolyte system varies between 10-4 and 10-5 Scm-1 at 25 degrees Celsius depending on the exact composition. The temperature dependence of the conductivity exhibits typical Vogel-Tamman-Fulcher (VTF) behavior. The thickness of the electrolyte between the two halves of the device could be adjusted by the use of a spacer technique in the range 10 - 150 micrometer. Optoelectrochemical measurements were conducted on electrochromic devices to study the kinetics of coloration and bleaching as a function of the number of switching cycles. At present, cells are constructed in two formats: 10 multiplied by 15 cm2 and 35 multiplied by 35 cm2. Switching times under one minute were achieved for the smaller format with a corresponding optical modulation between 75% to 20% (at lambda equals 0.633 micrometer). In the case of the larger format the switching time increases to several minutes due to the increase in geometric area.

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

1997-10-01

218

Sol-gel derived C-SiC composites and protective coatings for sustained durability in the space environment  

Microsoft Academic Search

Composites and coatings were produced via the fast sol-gel process of a mixture of alkoxysilane precursors. The composites were comprised of carbon fibers, fabrics, or their precursors as reinforcement, and sol-gel-derived silicon carbide as matrix, aiming at high-temperature stable ceramics that can be utilized for re-entry structures. The protective coatings were comprised of fluorine-rich sol-gel derived resins, which exhibit high

Yair Haruvy; Volker Liedtke

2003-01-01

219

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

220

Synthesis of nanocrystalline NiCuZn ferrite powders by sol-gel auto-combustion method  

NASA Astrophysics Data System (ADS)

A nitrate-citrate gel was prepared from metal nitrates and citric acid by sol-gel process, in order to synthesize Ni 0.25Cu 0.25Zn 0.50Fe 2O 4 ferrite. The thermal decomposition process was investigated by DTA-TG, IR and XRD techniques. The results revealed that the nitrate-citrate gel exhibits self-propagating combustion behavior. After combustion, the gel directly transformed into single-phase, nano-sized NiCuZn ferrite particles with spinel crystal structure. The synthesized powder can be densified at a temperature lower than 900°C. The sintered body possesses fine-grained microstructure, good frequency stability and high-quality factor compared to the sample prepared by conventional ceramic route.

Yue, Zhenxing; Zhou, Ji; Li, Longtu; Zhang, Hongguo; Gui, Zhilun

2000-01-01

221

Enhanced photoelectrochemical performance of Ti-doped hematite thin films prepared by the sol-gel method  

NASA Astrophysics Data System (ADS)

Ti-doped ?-Fe 2O 3 thin films were successfully prepared on FTO substrates by the sol-gel route. Hematite film was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The XRD data showed ?-Fe 2O 3 had a preferred (1 1 0) orientation which belonged to the rhombohedral system. Interestingly, the grains turned into worm-like shape after annealed at high temperature. The IPCE could reach 32.6% at 400 nm without any additional potential vs. SCE. Titanium in the lattice can affect the photo electro chemical performance positively by increasing the conductivity of the thin film. So the excited electrons and holes could live longer, rather than recombining with each other rapidly as undoped hematite. And the efficient carrier density on the Ti-doped anode surface was higher than the undoped anode, which contribute to the well PEC performance.

Lian, Xiaojuan; Yang, Xin; Liu, Shangjun; Xu, Ying; Jiang, Chunping; Chen, Jinwei; Wang, Ruilin

2012-01-01

222

Spectroscopic and electrochemical characterization of cytochrome c encapsulated in a bio sol-gel matrix.  

PubMed

Sol-gel technique represents a remarkably versatile method for protein encapsulation. To enhance sol-gel biocompatibility, systems envisaging the presence of calcium and phosphates in the sol-gel composition were recently prepared and investigated. Unfortunately, the low pH at which solutions were prepared (pH < 2.5) dramatically limited their application to proteins, because the acidic environment induces protein denaturation. In this paper we apply a new protocol based on the introduction of calcium nitrate to the inorganic phase, with formation of a binary bioactive system. In this case protein encapsulation results versatile and secure, being achieved at a pH close to neutrality (pH 6.0); also, the presence of calcium is expected to enhance system biocompatibility. To determine the properties of the salt-doped sol-gel and the influence exerted on entrapped biosystems, the structural and functional properties of embedded cytochrome c have been investigated. Data obtained indicate that the salt-doped sol-gel induces no significant change in the structure and the redox properties of the embedded protein; also, the matrix increases protein stability. Interestingly, the presence of calcium nitrate appears determinant for refolding of the acid-denatured protein. This is of interest in the perspective of future applications in biosensoristic area. PMID:18163198

Deriu, Daniela; Pagnotta, Sara Emanuela; Santucci, Roberto; Rosato, Nicola

2008-08-01

223

Vibrational spectroscopic studies of (3-mercaptopropyl)trimethoxylsilane sol-gel and its coating.  

PubMed

Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side. PMID:16165048

Li, Ying-Sing; Wang, Yu; Tran, Tuan; Perkins, Anshion

2005-10-01

224

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

225

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

NASA Astrophysics Data System (ADS)

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

Dejneka, Matthew J.

1995-01-01

226

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

227

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

228

Structural, optical and vibrational properties of sol gel titania valproic acid reservoirs  

NASA Astrophysics Data System (ADS)

Organically modified sol-gel derived titania xerogels were prepared by co-gellation of titanium n-butoxide and 2-propylpentanoic acid (valproic acid) at room temperature. Materials with different content of valproic acid were obtained varying the concentration of the drug, during the mixing stage of the sol-gel processing with two concentrations 400 and 800 mg/g of titania. Resulting xerogels were characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and electron microscopy techniques. Analysis of infrared spectra provides information on the interaction between titania and the adsorbed valproic acid. XRD show an amorphous structure at room temperature. SEM micrographs revealed that the nanoparticles of the xerogels form heterogeneous plates, meanwhile a homogeneous nanostructure was observed by TEM. This study shows the optical and structural properties of the materials and the chemical stability of the encapsulated drug, and suggests that these sol-gel titania are promising carriers for controlled drug release.

Lopez, T.; Ortiz-Islas, E.; Vinogradova, E.; Manjarrez, J.; Azamar, J. A.; Alvarado-Gil, J. J.; Quintana, P.

2006-10-01

229

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

SciTech Connect

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 oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17 g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.

Cervantes, O; Kuntz, J; Gash, A; Munir, Z

2009-02-13

230

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

231

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

232

Sol-gel phosphate-based glass for drug delivery applications.  

PubMed

Development of controlled, targeted drug delivery systems represents one of the frontier areas of biomaterials science, where a multidisciplinary approach is of direct benefit to human healthcare. We demonstrate herein the potential of sol-gel derived phosphate-based glass for use in drug delivery applications. Our low-temperature sol-gel synthesis of phosphate-based glasses has made it possible to incorporate relatively unstable functional molecules for controlled release. We demonstrate the potential of this approach by incorporating the chemotherapy agent cisplatin in a CaO-Na(2)O-P(2)O(5) glass. X-ray absorption spectroscopy is used to show that the chlorine ligands of cisplatin undergo exchange with oxygen during the synthesis, consistent with binding to the phosphate groups of the sol-gel. UV-visible spectroscopy reveals the subsequent release of cisplatin into an aqueous medium. PMID:20819917

Pickup, David M; Newport, Robert J; Knowles, Jonathan C

2012-01-01

233

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

234

Nanostructure magneto-optical thin films of rare earth (RE=Gd,Tb,Dy) doped cobalt spinel by sol-gel synthesis  

NASA Astrophysics Data System (ADS)

Nanocrystalline CoFe1.9RE0.1O4 [rare earth (RE=Gd,Tb,Dy)] films have been prepared by the sol-gel route, and their polar magneto-optical (MO) Kerr rotation and ellipticity have been determined in the spectral range of 4000-8000 Å. The films are composed of nanometer grains with the spinel structure. RE doped cobalt spinel ferrites are found to have dramatic changes in magnetic and MO properties, with increases in their coercive force and enhancement of the MO rotation in the Tb3+ doped sample.

Cheng, Fuxiang; Liao, Chunsheng; Kuang, Junfeng; Xu, Zhigang; Yan, Chunhua; Chen, Liangyao; Zhao, Haibin; Liu, Zhu

1999-03-01

235

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

236

Ionic conductivity of Bi{sub 2}Ni{sub x}V{sub 1?x}O{sub 5.5?3x/2} (0.1 ? x ? 0.2) oxides prepared by a low temperature sol-gel route  

SciTech Connect

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 Bi{sub 4}V{sub 2}O{sub 11} 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 Bi{sub 2}Ni{sub x}V{sub 1?x}O{sub 5.5?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{sup ?3} S cm{sup ?1}, 1.2 × 10{sup ?3} S cm{sup ?1}, and 8.2 × 10{sup ?4} S cm{sup ?1}, for x = 0.1; 0.15; and 0.2; respectively; and at 600 °C were 1.1 × 10{sup ?1} S cm{sup ?1}, 5.3 × 10{sup ?2} S cm{sup ?1}, and 2.8 ×10{sup ?2} S cm{sup ?1}, for x = 0.1; 0.15; and 0.2; respectively.

Rusli, Rolan; Patah, Aep, E-mail: ismu@chem.itb.ac.id; Prijamboedi, Bambang, E-mail: ismu@chem.itb.ac.id; Ismunandar, E-mail: ismu@chem.itb.ac.id [Inorganic and Physical Chemistry Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia); Abrahams, Isaac [Materials Research Institute, School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

2014-03-24

237

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

238

Organic supramolecular architectures and their sol-gel transcription to Silica nanotubes.  

PubMed

The design of artificial models of "biomineralization" processes that utilize sol-gel polymerization has led to a merging of inorganic materials research and supramolecular organic chemistry. This article introduces self-assembled superstructures of sugar-integrated and crown-appended cholesterol gelators, which are used as versatile building blocks in organogels and as templates for sol-gel transcription. This article focuses on the use of self-assembled organic superstructures in the creation of novel inorganic materials with controlled morphologies. PMID:14595830

Jung, Jong Hwa; Shinkai, Seiji; Shimizu, Toshimi

2003-01-01

239

Scintillators for Alpha and Neutron Radiations Synthesized by Room Temperature Sol–Gel Processing  

Microsoft Academic Search

Solid-state scintillating materials were synthesized by the co-doping of sol–gel components with neutron absorbers [6Li and 10B], organic fluorescence sensitizers such as salicylic acid and 2,5-diphenyloxazole (PPO) and activator 1,4-bis-2-(5-phenyloxazolyl)-benzene (POPOP). The room-temperature sol–gel process through the addition of organic polymers is the key to the successful entrapment of the organic sensitizers and activator in inorganic matrixes. These transparent or

Hee-Jung Im; Carl Willis; Suree Saengkerdsub; Rajev Makote; Michelle D. Pawel; Sheng Dai

2004-01-01

240

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

PubMed Central

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

2013-01-01

241

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

SciTech Connect

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

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

2014-10-21

242

Transmission Electron Microscopy Characterization and Application of Sol-Gel Membranes  

NASA Astrophysics Data System (ADS)

: Using standard square mesh grids as supports, we have prepared sol-gel membranes from a functionalized silane precursor, bis[3-(triethoxysilyl)propyl]tetrasulfide in various organic solvents. These mesh-supported membranes allow direct characterization of their microstructure and morphology by transmission electron microscopy (TEM). Homogeneous membranes without prominent microstructural features (or featureless) at nanometer scale were obtained from dimethyl formamide (DMF), isopropanol, and butanol solutions. However, highly porous membranes were produced from DMF and ethylene glycol binary system. Heterogeneous membranes filled with nanoparticles were formed from dimethyl sulfoxide solution. The featureless sol-gel membranes with tunable performances provide a useful alternative as supporting films for TEM applications.

Guo, Yizhu; Gonzalez, Sandra; Guadalupe, Ana R.

1999-11-01

243

Sol-gel Encapsulation of Biomolecules and Cells for Medicinal Applications.  

PubMed

The sol-gel process provides a robust and versatile technology for the immobilization of biologicals. A wide range of inorganic, composites and hybrid materials can be prepared to encapsulate molecular drugs, proteins, antibodies/antigens, enzymes, nucleic acids, prokaryotic and eukaryotic cells into bulk gels, particles and films. This review describes the applications of sol-gel encapsulation relevant to medicinal chemistry focusing on the recent development of biosensors as well as systems for production, screening and delivery of bioactive compounds and biomaterials. PMID:25547970

Wang, Xiaolin; Ahmed, Nada Ben; Alvarez, Gisela S; Tuttolomondo, Maria V; Helary, Christophe; Desimone, Martin F; Coradin, Thibaud

2015-01-01

244

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

245

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

246

Patterned ZrO2 Sol Gels for DNA Immobilisation. M. Manning, M. Biancardo, H. Doyle, M. Sheehan, G. Redmond.  

E-print Network

Patterned ZrO2 Sol Gels for DNA Immobilisation. M. Manning, M. Biancardo, H. Doyle, M. Sheehan, G for the formation of chemically active microporous ZrO2 films on standard microscope glass slides. Through, this attachment method successfully provides high quality results. ZrO2 sol/gel coating with its rough and open

247

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

EPA Science Inventory

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

248

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

249

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

250

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

251

Effect of CO2 laser irradiation on the performances of sol-gel-derived Er3+-activated SiO2 - ZrO2 and SiO2 - HfO2 planar waveguides  

Microsoft Academic Search

Erbium activated SiO2-ZrO2 and SiO2-HfO2 planar waveguides doped with Er3+ ranging from 0.5 to 5 mol% were prepared by sol-gel route using dip-coating deposition on silica glass substrates. All the planar waveguides were optimized in order to confine one propagating mode at 1550 nm. The aim of this work is to present an alternative method for planar optical waveguides processing

C. Goyes; M. Ferrari; C. Armellini; A. Chiasera; Y. Jestin; G. C. Righini; A. Casas; C. Meacock; E. Solarte

2007-01-01

252

Glucose sensing based on the intrinsic fluorescence of sol-gel immobilized yeast hexokinase  

E-print Network

, particularly in type 1 diabetes. Diabetic patients cur- rently test blood glucose levels using finger-prick sam rights reserved. Keywords: Glucose; Glucose sensor; Sol gel; Hexokinase; Fluorescence Although good blood difficult to achieve, with wide and unpredictable swings in blood glucose concentration often occurring

Strathclyde, University of

253

Submicron metal oxide structures by a sol-gel process on patterned substrates  

Microsoft Academic Search

We report about a combination of micro-contact-printing and the sol-gel technique which results in structures in the micron- and submicron range. This technique which is here demonstrated on electrochromic tungsten oxide does not rely on vacuum methods and may therefore be easily upscaled to large areas.

Clemens Bechinger; Hans Muffler; Claudia Schäfle; Olle Sundberg; Paul Leiderer

2000-01-01

254

Sol-gel chemical sensors for surface-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

1999-02-01

255

Aging effect on the phase evolution of water-based sol–gel hydroxyapatite  

Microsoft Academic Search

In a number of recent reports on the synthesis of sol–gel hydroxyapatite, aging of the precursor solution has been found to be critical in developing an apatitic phase. Critical aging time is required to complete reaction between Ca and P molecular precursors to form a desired intermediate complex that permits a further transformation to apatite phase under appropriate thermal treatment.

Dean-Mo Liu; T. Troczynski; Wenjea J. Tseng

2002-01-01

256

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

257

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

PubMed Central

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

2012-01-01

258

A composite sol–gel\\/fluoropolymer matrix for dissolved oxygen optical sensing  

Microsoft Academic Search

A thin film dissolved oxygen optical sensor was fabricated by encapsulating the phosphorescent dye erythrosin B in a sol–gel\\/fluoropolymer composite matrix. Strong phosphorescence, which was efficiently quenched by dissolved oxygen, was observed. The sensor was stable, optically transparent, resistant to contamination, with good mechanical properties. Fast response, coupled with good sensitivity and resistance to leaching, were also exhibited by this

R. N. Gillanders; M. C. Tedford; P. J. Crilly; R. T. Bailey

2004-01-01

259

Tailoring of sol-gel films for optical sensing of oxygen in gas and aqueous phase.  

PubMed

Sol-gel-based optical sensors for both gas-phase and dissolved oxygen have been developed. Both sensors operate on the principle of fluorescence quenching of a ruthenium complex which has been entrapped in a porous sol-gel silica film. A comprehensive investigation was carried out in order to establish optimal film-processing parameters for the two sensing environments. Both tetraethoxysilane and organically modified sol-gel precursors such as methyltriethoxysilane and ethyltriethoxysilane were used. Film hydrophobicity increases as a function of modified precursor content, and this was correlated with enhanced dissolved oxygen (DO) sensor performance. Extending the aliphatic group of the modified precursor further improved DO sensitivity. The influence of water/precursor molar ratio, R, on the sol-gel film microstructure was investigated. R value tailoring of the microstructure and film surface hydrophobicity tailoring were correlated with oxygen diffusion behavior in the films via the Stern-Volmer constants for both gas phase and DO sensing. Excellent performance characteristics were measured for both gas-phase and DO oxygen sensors. The long-term quenching stability of DO sensing films was established over a period of 6 months. PMID:21644598

McDonagh, C; Maccraith, B D; McEvoy, A K

1998-01-01

260

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

261

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

E-print Network

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

Wang, Ping

262

Micropatterning and crystallization of sol-gel-derived dielectric film by laser direct writing  

Microsoft Academic Search

Low temperature crystallization and the micropatterning of lead zirconate titanate (PZT) film were achieved by laser direct writing method using a sol-gel derived precursor film. After scanning of an Ar ion laser beam through an objective lens, the etching of the unirradiated area of the precursor film with an acidic solution gave micropatterns with a resolution of several mum. The

Akira Watanabe; Tomokazu Tanase; Kenji Miyajima; Yoshio Kobayashi; Mikio Konno

2010-01-01

263

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

E-print Network

Mullite interaction with bismuth oxide from minerals and sol-gel processes F. Gridi-Bennadji * , J doped by bismuth oxide was studied by TGA and DTA, X ray diffraction, and electron microscopy (SEM muscovite. With addition of bismuth oxide, SEM observations point to the strong accentuation of mullite

Paris-Sud XI, Université de

264

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

265

Enhanced Proteolytic Activity of Covalently Bound Enzymes in Photopolymerized Sol Gel  

E-print Network

Enhanced Proteolytic Activity of Covalently Bound Enzymes in Photopolymerized Sol Gel Maria T (BAEE) and two peptides, neuro- tensin and insulin chain B. The coupling of the enzyme to the monolith on the carboxyl side of methionine residues whereas the enzyme trypsin specifically hydrolyzes peptide bonds

Zare, Richard N.

266

Hybrid Silica-PVA Nanofibers via Sol-Gel Electrospinning Tahira Pirzada,,  

E-print Network

Hybrid Silica-PVA Nanofibers via Sol-Gel Electrospinning Tahira Pirzada,,§ Sara A. Arvidson,,§ Carl (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor,4,11 Electrospinning is a decades-old technique which draws very fine fibers from a viscous liquid (usually a polymer

Khan, Saad A.

267

OPTIMIZATION OF ALKYL ESTER PRODUCTION FROM GREASE USING A PHYLLOSILICATE SOL-GEL IMMOBILIZED LIPASE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Simple alkyl ester derivatives of restaurant grease were prepared using a lipase from Pseudomonas cepacia immobilized within a phyllosilicate sol-gel matrix as biocatalyst. Alcoholysis reactions of grease were carried out in solvent-free media using a one step addition of alcohol to reaction mixtur...

268

Biocompatibility and Reduced Drug Absorption of Sol-Gel-Treated Poly(dimethyl siloxane) for  

E-print Network

, the porous, hydrophobic polymer matrix of PDMS rapidly absorbs small hydrophobic molecules, including such substances in PDMS microfluidic devices. This study presents evidence that a sol-gel treatment of PDMS absorption and diffusion of small hydrophobic molecules into PDMS limits its use in some biological

Quake, Stephen R.

269

Long-term durability of sol–gel porous coatings for solar glass covers  

Microsoft Academic Search

The application of antireflective coatings to the glass covers of solar thermal collectors, allows to increase the efficiency of the whole system. In this sense, sol–gel silica porous coatings have been deposited on borosilicate glass and solar transmittance values as high as 0.97 have been obtained. The densification process of the films has been studied and the optimal heat treatment

G. San Vicente; R. Bayón; N. Germán; A. Morales

2009-01-01

270

Characterization of zirconia-based catalysts prepared by precipitation, calcination, and modified sol-gel methods  

SciTech Connect

Zirconia-based catalysts were synthesized by various methods and were evaluated for the synthesis of isobutane and isobutene from CO hydrogenation. The methods of preparation included precipitation (ZrO[sub 2] (PPT)), calcination of zirconyl salt (ZrO[sub 2] (H-0304)), and a modified sol-gel method (ZrO[sub 2] (sol-gel)). Acid-base properties of zirconia were affected by the method of preparation. The number of acidic sites on the surface follows the order of ZrO[sub 2] (PPT) > ZrO[sub 2] (sol-gel) [approx] ZrO[sub 2] (H-0304), and the number of basic sites follows ZrO[sub 2] (PPT) > ZrO[sub 2] (sol-gel) > ZrO[sub 2] (H-0304). Furthermore, adding aluminum increased the numbers of acidic and basic sites, and adding silicon increased the number of acidic sites but reduced the number of basic sites. The product distribution of CO hydrogenation depended on the acid-base properties of the catalyst, and the activity tests indicated that a large ratio of basic to acidic sites is a requirement for an active catalyst to produce isobutane and isobutene from CO hydrogenation.

Feng, Z.; Postula, W.S.; Akgerman, A.; Anthony, R.G. (Texas A and M Univ., College Station, TX (United States))

1995-01-01

271

Investigation of an automated cleaning system for LMJ coating sol-gel process  

NASA Astrophysics Data System (ADS)

The French Commission for Atomic Energy is currently involved in a project which consists in the construction of a 2MJ/500TW (351nm) laser, so called LMJ (Megajoule-class laser) devoted to Inertial Confinement Fusion (ICF) research in France[1]. For this high power lasers, the sol-gel process[2] has been selected for 95% of laser optical coated area because of room temperature and atmospheric pressure conditions with guarantee for high optical and laser induced damage threshold (LIDT) performances at a low cost compared to conventional vacuum deposition processes. The production rate of sol-gel coatings for the LMJ optical components will require an automated cleaning surface step during sol-gel process. We are investigating a spraying system and wash cycles compatible with the two sol-gel deposition methods: dip and laminar-flow coating. The challenge is to achieve the same cleaned optical surfaces as manual process without using organic solvents. Therefore the main specifications of the cleaning quality are the following ones: a high surface energy over all optical sides (up to 400×400 mm2 area) and no degradation of polished sides (surface defects and LIDT). We present the metrologies carried out and the first results obtained from different wash cycles. These one mainly consist in measurement of contact angles, defects inspections under specific lighting conditions and LIDT tests. Several parameters of wash cycles have been investigated such as washing and rinsing temperatures, water quality, type and concentration of detergents, wettability effects...

Lavastre, E.; Fontaine, S.; Bergez, R.; Wender, P.; Cormont, P.; Pellegrini, C.; Beaurain, L.; Belleville, P.

2008-09-01

272

Properties of sol–gel derived mesoporous aluminas as metal traps  

Microsoft Academic Search

The performance of fluid catalytic cracking (FCC) catalysts for processing heavy feedstocks is often determined by the tolerance of the catalyst to metal contaminants. Different approaches are used to manage contaminant metals. In this paper, the mesoporous sol–gel derived alumina properties are studied with respect to its behavior in the presence of nickel, after different thermal and steaming treatments. The

A. Vargas; C. Maldonado; J. A. Montoya; L. Noreña; J. Morales

2004-01-01

273

Energetic Nanocomposites with Sol-gel Chemistry: Synthesis, Safety, and Characterization  

Microsoft Academic Search

The preparation and characterization of energetic composite materials containing nanometer-sized constituents is currently a very active and exciting area of research at laboratories around the world. Some of these efforts have produced materials that have shown very unique and important properties relative to traditional energetic materials. We have previously reported on the use of sol-gel chemical methods to prepare energetic

A E Gash; R L Simpson; J H Satcher

2002-01-01

274

Energetic Nanocomposites with Sol-gel Chemistry: Synthesis, Safety and Characterization  

Microsoft Academic Search

The preparation and characterization of energetic composite materials containing nanometer-sized constituents is currently a very active and exciting area of research at laboratories around the world. Some of these efforts have produced materials that have shown very unique and important properties relative to traditional energetic materials. We have previously reported on the use of sol-gel chemical methods to prepare energetic

A E Gash; R L Simpson; J H Satcher

2002-01-01

275

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

276

Investigation on the pressure infiltration of sol-gel processed textile ceramic matrix composites  

Microsoft Academic Search

A pressure infiltration apparatus was used to fabricate textile ceramic matrix composites using sol-gel processing with added solid particles. A parabolic rate kinetics model for the infiltration process has been developed and experimentally verified. Darcy's law and a global permeability of the whole material system were adopted in the model. Experiments were conducted using both a 3-d angle interlock and

Hsien-Kuang Liu

1996-01-01

277

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

278

Investigation of optical properties of anthocyanin doped into sol-gel based matrix  

NASA Astrophysics Data System (ADS)

Anthocyanin dye was extracted from petal of Hibiscus rosasinensis (Bunga Raya) and doped into sol-gel based matrix to investigate an effect of pH change on its optical properties. Sol-gel matrix based on Vinyl triethoxysilene (VTES) as a precursor was prepared through Sol-gel process at pH 7. The sol was doped with 0.1% of Anthocyanin and the same amount of dye was also dissolved in ethanol as a comparative sample. Hydrochloric Acid, HCl and Tetramethylammonium Hydroxide, TMAH were used to change the pH value by adding them at various concentrations into each sample. The emission spectra and chemical structures of the samples were measured by Spectrofluorometer and Fourier Transform Infrared (FTIR) respectively. When excited at 410 nm, two emission peaks at about 492 and 574 nm were observed for Anthocyanin in acidic environment both in ethanol and VTES sol. In base environment however, only Anthocyanin dissolved in ethanol produced emission peak with a single peak at about 539 nm. The sensitivity of Anthocyanin dye toward pH changes in VTES open a possibility to use it as sensing element in which sol-gel based matrix are known to have higher mechanical strength and thermal stability.

Hashim, Hasrina; Abdul Aziz, Nik Mohd Azmi Nik; Isnin, Aishah

2012-06-01

279

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

E-print Network

and enzymes embedded in these glasses is enhanced with regard to temperature, pH, and chemical denaturation.5 to water (R value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady

Fayer, Michael D.

280

HIGH PURITY FERROELECTRIC MATERIALS BY SOL-GEL PROCESS FOR MICROWAVE APPLICATIONS  

E-print Network

titanate (EITO), strontium-modified barium titanate (EST), lead titanate (PTO) powers and thin films-Gel process [4], [5]. We have developed a new method of synthesizing Sol-Gel precursor for making barium, For the BTO the precursor is prepared with barium hydroxide octahydrate, Ba(OH)2-8H20, which is dissolved

De Flaviis, Franco

281

HIGH PURITY FERROELECTRIC MATERIALS BY SOL-GEL PROCESS FOR MICROWAVE APPLICATIONS  

E-print Network

of synthesizing sol-gel precursor for making barium titanate (BTO), strontium- modified barium titanate (BST) powders and thin films. The precursor is prepared with barium hydroxide octahydrate, Ba(OH)2-8H2O, which to the solution to yield a 1:1 molar ratio of barium-titanium complex alkoxide solution. This precursor

De Flaviis, Franco

282

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

Microsoft Academic Search

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

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

2006-01-01

283

Sol-gel entrapped chromium(VI): a new selective, efficient and recyclable oxidizing system  

Microsoft Academic Search

The sol-gel entrapment of chromium(VI) within a silica matrix, obtained by oxidation with ozone of the corresponding entrapped chromium(III), was found to be an efficient and recyclable oxidizing system (at least up to 16 times) for benzylic alcohols. No leaching of chromium in solution was observed, which prevented any environmental pollution.

Michelangelo Gruttadauria; Leonarda F Liotta; Renato Noto; Giulio Deganello

2001-01-01

284

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

Microsoft Academic Search

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

Vivek Babu Kandimalla; Vijay Shyam Tripathi; Huangxian Ju

2006-01-01

285

An Efficient Sol-Gel Reactor for Antibody-Catalyzed Transformations  

E-print Network

An Efficient Sol-Gel Reactor for Antibody-Catalyzed Transformations Doron Shabat, Flavio Grynszpan in bacteria, plant, seeds, and algae, as well as immobilization to facilitate the recovery of the catalyst, polycellulose, etc., may be packed in columns and used in continuous- flow reactors, but their effective

Keinan, Ehud

286

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

E-print Network

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

Sottos, Nancy R.

287

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

288

Conformal sol-gel coatings on three-dimensional nanostructured templates  

NASA Astrophysics Data System (ADS)

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

Weatherspoon, Michael R.

289

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass  

PubMed Central

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte. These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron biosensor, pyoverdin (a fluorescent siderophore produced by Pseudomonas spp.) was immobilized in 3 formulations of porous sol-gel glass. The formulations, A, B, and C, varied in the amount of water added, resulting in respective R values (molar ratio of water:silicon) of 5.6, 8.2, and 10.8. Pyoverdin-doped sol-gel pellets were placed in a flow cell in a fluorometer and the fluorescence quenching was measured as pellets were exposed to 0.28 - 0.56 mM iron (II or III). After 10 minutes of exposure to iron, ferrous ion caused a small fluorescence quenching (89 - 97% of the initial fluorescence, over the range of iron tested) while ferric ion caused much greater quenching (65 - 88%). The most specific and linear response was observed for pyoverdin immobilized in sol-gel C. In contrast, a solution of pyoverdin (3.0 ?M) exposed to iron (II or III) for 10 minutes showed an increase in fluorescence (101 - 114%) at low ferrous concentrations (0.45 - 2.18 ?M) while exposure to all ferric ion concentrations (0.45 - 3.03 ?M) caused quenching. In summary, the iron specificity of pyoverdin was improved by immobilizing it in sol-gel glass C. PMID:21554740

2011-01-01

290

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

SciTech Connect

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

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

1989-12-31

291

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

SciTech Connect

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

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

1989-01-01

292

Nonlinear solid-state filter based on photochromism induced by 2-photon absorption in a dye-doped sol-gel  

NASA Astrophysics Data System (ADS)

There is much interest in enhancement of the absorbance performance of nonlinear absorber solid-state filters. In this work we present an advanced reversible nonlinear filter based on a dye-doped sol-gel matrix. The absorbance enhancement was achieved by using a combination of two absorption mechanisms in the same molecule; a photochromic absorption which is induced by 2-photon absorption (2PA). The 2PA serves as the trigger for initiating the photochromism through Förster-resonance-energy-transfer (FRET) between the fluorescent donor and the photochromic acceptor. We synthesized a new bifunctional-chromophore that incorporated a carbazole-derived 2PA fluorescent donor and a chromene-derived photochromic acceptor, covalently linked together in a single molecule by a ~6 Å carboxyl group or oxygen bridge. The bifunctional-chromophore was doped in an inorganic-organic hybrid matrix prepared by the fast-sol-gel process. These materials solidify without shrinkage or formation of cracks and present promising properties as optical matrices for smart filters. The dye-doped sol-gel disc presents high transparency in the visible region ("colorless"), which under UV-irradiation (one-photon absorption in the photochromic part of the molecule), transforms into a strongly absorbing filter ("dark colored"), due to the conversion of the photochromic moiety to its "open" absorbing form. We have demonstrated that this ring-opening can also be induced by visible-light (620 nm) using the 2PA carbazole-derived moiety of the molecule. We have studied the fabrication routes and optical performance of these filters. We present studies of the 2PA mechanism of the carbazole derivative, FRET efficiency of the combined-molecule as well as in solutions of the individual moieties, and reversible dynamics of the photochromic moiety.

Gvishi, Raz; Zhao, Peng; Hu, Honghua; Strum, Galit; Tal, Amir; Grinvald, Shmuel; Bar, Galit; Bekere, Laura; Lokshin, Vladimir; Khodorkovsky, Vladimir; Sigalov, Mark; Hagan, David; Van Stryland, Eric

2014-10-01

293

Germania-based, sol-gel hybrid organic-inorganic coatings for capillary microextraction and gas chromatography.  

PubMed

Germania-based, sol-gel hybrid organic-inorganic coatings were developed for capillary microextraction and gas chromatography (GC). Being an isostructural analogue of SiO2, GeO2 is compatible with the silica network. Because of this similarity, germania-based materials possess great potential for being used in the areas of chromatographic separation and sample preparation. These possibilities, however, remain practically unexplored. To our knowledge, this is the first instance that a germania-based hybrid sol-gel material is used as a sorbent in analytical sample preparation or chromatographic separation. Tetramethoxygermane was used as a precursor to create a sol-gel network via hydrolytic polycondensation reactions performed within a fused-silica capillary. The growing sol-gel germania network was simultaneously reacted with an organic ligand that contained sol-gel-active sites in its chemical structure. Three different sol-gel-active ligands were used: (a) hydroxy-terminated poly(dimethylsiloxane), (b) hydroxy-terminated poly(dimethyldiphenylsiloxane), and (c) 3-aminopropyltrimethoxysilane. Sol-gel germania-coated capillaries of desired polarity and extraction selectivity were prepared by using an appropriately selected sol-gel-active ligand in the sol solution. These capillaries were further used to extract trace concentrations of polycyclic aromatic hydrocarbons, aldehydes, ketones, alcohols, phenols, and free fatty acids from aqueous samples. The extracted solutes were further analyzed by GC-FID. The new germania-based coatings showed excellent stability under harsh operation conditions involving extreme pH values, high temperatures, and aggressive solvents. Our preliminary results also indicate that sol-gel hybrid germania coatings have the potential to offer great analytical performance as GC stationary phases. PMID:17994707

Fang, Li; Kulkarni, Sameer; Alhooshani, Khalid; Malik, Abdul

2007-12-15

294

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

295

Erbium-doped sol-gel materials for optical applications  

Microsoft Academic Search

A new chemical nanotechnological route for the preparation of fully densified doped SiO2 coatings with thicknesses in the low µm-range on Si- and SiO2-wafers has been developed. Beside pure SiO2 coatings, that might be useful as a buffer layer on silicon, silicate layers with increased refractive index are needed for planar waveguide application. Therefore, a synthesis for the preparation of

Anette Berni; Martin Mennig; Helmut K. Schmidt

2003-01-01

296

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

297

One-pot synthesis of CdS nanoparticles exhibiting quantum size effect prepared within a sol-gel derived ureasilicate matrix  

NASA Astrophysics Data System (ADS)

This paper describes a novel single-pot synthesis process based on sol-gel for the production of a highly transparent hybrid matrix containing CdS nanoparticles (NPs). The reaction between cadmium and sulphide ions in the presence of 3-mercaptopropyltrimethoxysilane (MPTMS) that originates the formation of quantum confined CdS NPs occurs simultaneously with the condensation and polymerization of the gel precursors that evolves to a macromolecular hybrid organic-inorganic network. The obtained xerogel matrix is based on the reaction of organically modified alkoxysilane (3-isocyanatepropyltriethoxysilane) and a di-amine functionalized oligopolyoxyethylene (Jeffamine ED-600). The final material is characterized as highly transparent, homogeneous and flexible xerogel incorporating stabilized and high crystalline CdS NPs that exhibit size-dependent optical properties due to quantum confinement of photogenerated e-h pairs as observed from UV-visible and photoluminescence spectroscopy and HRTEM microscopy measurements. The developed approach has obvious advantages comparatively to the alternative and more complex routes of production of composite materials with embedded semiconductor NPs because of the simplified one-pot preparative procedure used. The developed sol-gel process allows the control of the optical characteristics of the obtained CdS NPs embedded within the network by adjusting the molar ratio between cadmium ion and MPTMS and between cadmium and sulphide ions.

Gonçalves, Luis F. F. F.; Kanodarwala, Fehmida K.; Stride, John A.; Silva, Carlos J. R.; Gomes, Maria J. M.

2013-12-01

298

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

299

Dielectric and Structural Properties of Barium Strontium Titanate (BST) and Bismuth Titanante (BiTi) Sol-Gel Thin Films  

NASA Astrophysics Data System (ADS)

We have used several methods (sol-gel, cvd, and laser ablation) to fabricate thin (less than 100 nm thick) high permittivity, perovskite films for future use in integrated circuit applications such as DRAMs and NVRAMs. BST and BiTi films made using sol-gel techniques have allowed fast turn around time for testing various processing and integration techniques. The sol-gel films are generally made in several layers with individual layer thicknesses varying from about 10 to 50 nm. SEM, TEM and X-ray studies reveal columnar grains roughly equal in size to the film thickness and micrographs from capacitor test structures will be shown. Edge coverage, an important property for applications, will be demonstrated for the sol-gel films. Electrical data including the complex permittivity measured out to about 6 GHz are also presented. Charge storage effects will be compared for BiTi grown both on Pt and thin oxidized Ti surfaces.

Laibowitz, R. B.; Shaw, T. N.; Duncombe, P. R.; Neumeyer, D.; Grill, A.; Kotecki, D.; Saenger, K. L.; Baniecki, J. D.; Ma, Q. Y.

1997-03-01

300

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

301

Non-aqueous primary cell  

NASA Astrophysics Data System (ADS)

This patent application relates to electrochemical cells and especially to high-energy, liquid cathode, non-aqueous lithium electrochemical cells free from highly toxic materials. A non-aqueous lithium electrochemical cell is described which includes a halocarbon cathode depolarizer which is 1,2-dichloroethane, 1.1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2-dichloro-1,1-difluoroethane or mixtures thereof and a cathode catalyst which is copper, rhodium, palladium, cobalt phthalocyanine, nickel phthalocyanine, iron phthalocyanine, a cobalt tetraaza-(14)-annulene, a nickel tetraaza-(14)-annulene, a iron tetraaza-(14)-annulene, a cobalt porphyrin, a nickel porphyrin, a iron porphyrin, or a mixture thereof.

James, S. D.; Smith, P. H.; Oneill, K. M.; Wilson, M. H.

1986-05-01

302

Sol-gel solution-deposited InGaZnO thin film transistors.  

PubMed

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

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

2014-03-26

303

The Physics of Evaporation-Induced Assembly of Sol-Gel Materials  

SciTech Connect

Remarkable materials ordered at the nanoscale emerge when a sol-gel solution becomes co-organized with a surfactant. At sufficiently high concentration, the surfactant forms crystalline or liquid-crystalline arrays of micelles in the presence of the sol-gel, and as gelation proceeds the arrays become locked into the gel. Recent experiments demonstrate that the degree of order in the resulting mesoporous ceramic phase can be enhanced and controlled by continuous dip coating in which the solution, initially dilute, evolves through the critical micelle concentration by steady-state evaporation. The long-range order and microstructural orientation in these films suggest that the propagation of a critical-micelle-concentration transition front, with large physico-chemical gradients, promotes oriented self assembly of surfactant aggregates. This steep-gradient view is supported by results from unsteady evaporation of aerosols of similar solutions, in which internally well-ordered but complex particles are formed.

HURD,ALAN J.; STEINBERG,LEV

2000-07-24

304

Treatments of paper surfaces with sol-gel coatings for laminated plywood  

NASA Astrophysics Data System (ADS)

Two silane-based hybrid coatings were developed for surface modification of paper samples with an attempt to improve the hydrophobic properties of the paper surfaces. A phenolic resin was used along with the sol-gel coatings to impregnate the paper samples before they were pressed on to plywood surfaces. The surface characteristics of the sol-gel-coated paper were investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), confocal laser scanning microscopy (CLSM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface chemical properties and water absorption of the laminated plywood was also evaluated. It was observed that the hybrid coatings had clearly different effect on the surface properties of the base paper compared to the industrially impregnated paper. The water absorption of the laminated plywood was decreased the most effectively by mixing the phenolic resin with the coating having an octyl group attached to the silane backbone.

Wang, Shaoxia; Jämsä, Saila; Mahlberg, Riitta; Ihalainen, Petri; Nikkola, Juha; Mannila, Juha; Ritschkoff, Anne-Christine; Peltonen, Jouko

2014-01-01

305

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

306

High-efficiency sol-gel antireflection coatings for astronomical optics  

NASA Astrophysics Data System (ADS)

The antireflective properties of silica sol-gel coatings have been known for some time, and such coatings have bene used to reduce losses in the optical elements of high- powered lasers used in fusion experiments. Research at DAO has developed the technology to the pont where optical elements in three 4-meter class telescopes at CFHT, KPNO, and CTIO have benefitted from coatings made form high- efficiency sol-gel films. The process is attractive because it is simple to apply, is inexpensive, and is as effective as multi-layer vacuum-deposited coatings which it can replace. A description is given of the basic chemistry involved and the techniques used to apply the coatings. Techniques used to improve the durability of the films by hardening and waterproofing are described, as well as a two- layer coating in combination with magnesium fluoride.

Stilburn, James R.

2000-08-01

307

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

308

Dynamic heterogeneity of a colloidal solution near the sol-gel transition  

NASA Astrophysics Data System (ADS)

The results of the simulation of the dynamics of particles in a colloidal solution in the vicinity of the sol-gel transition are presented. The Van Hove correlation function, incoherent scattering function, and mean-square displacement of particles at different temperatures and volume densities have been calculated from the simulation data. The effects of dynamic heterogeneity have been evaluated numerically and the gelation temperature at different volume densities has been determined using the non-Gaussian parameter. It has been shown that the specific features observed in the dynamics of particles in the colloidal solution near the sol-gel transition are explained by the conventional separation of the particles in the system into fast particles, which contribute to translational diffusion, and slow particles, which participate predominantly in vibrational processes.

Mokshin, A. V.; Zabegaev, S. O.; Khusnutdinoff, R. M.

2011-03-01

309

Modeling of core-shell silver nanoparticles in nanostructured sol-gel thin films  

NASA Astrophysics Data System (ADS)

Silver nanoparticles were obtained by UV radiation of silica films containing Ag + ions. 2d-hexagonal nanostructured sol-gel thin films were prepared by dip-coating method using the non-ionic diblock copolymer Brij58 to produce channels into the film, which house the silver nanoparticles. An absorption band located at 438 nm was detected; it corresponds to the surface plasmon resonance. High resolution transmission electronic microscopy measurements show core-shell structures of silver-silver oxide nanoparticles in these sol-gel silica films. These optical properties were modeled and well fitted with the Gans theory considering refractive index higher than the one coming from host matrix. This index is explained because the silver oxide shell modifies the local surrounding medium of the metallic nanoparticles and therefore plays an important role in the optical properties of the films.

Valverde-Aguilar, Guadalupe; Rentería, Víctor; García-Macedo, Jorge A.

2007-09-01

310

The role of temperature in forming sol-gel biocomposites containing polydopamine.  

PubMed

To further improve the physical strength and biomedical applicability of bioceramicsbuilt on hydroxyapatite-gelatin (HAp-Gel) and siloxane sol-gel reactions, we incorporated mussel adhesive inspired polydopamine (PD) into our original composite based on HAp-Gel cross-linked with siloxane. Surprisingly, with the addition of PD, we observed that the processing conditions and temperatures play an important role in the structure and performance of these materials. A systematic study to investigate this temperature dependence behavior discloses that the rate of crosslinking of silane during the sol-gel process is significantly influenced by the temperature, whereas the polymerization of the dopamine only shows minor temperature dependence. With this discovery, we report an innovative thermal process for the design and application of these biocomposites. PMID:25485111

Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

2014-11-28

311

Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating  

DOEpatents

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

312

Sol gel based fiber optic sensor for blook pH measurement  

SciTech Connect

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

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

1996-12-19

313

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

PubMed Central

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

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

2010-01-01

314

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

NASA Technical Reports Server (NTRS)

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

1982-01-01

315

Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest  

NASA Astrophysics Data System (ADS)

The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach. Dedicated to the pioneer of sol-gel enzyme immobilization, Professor David Avnir, on the occasion of his 65th birthday.

Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T.

2014-05-01

316

Sol–gel synthesis of inorganic complex fluorides using trifluoroacetic acid  

Microsoft Academic Search

A sol–gel method to prepare inorganic complex fluorides, SrAlF5 and BaMgF4 is described. Metal acetates and alkoxide were used as starting materials, and trifluoroacetic acid was used as a fluorine source. The formation of the fluorides was examined using thermal analysis, X-ray diffraction (XRD) and infrared (IR) absorption. The fluorides were formed through the highly exothermic decomposition reaction of trifluoroacetate

Shinobu Fujihara; Sachiko Ono; Yoko Kishiki; Munehiro Tada; Toshio Kimura

2000-01-01

317

Investigation of sol–gel prepared Ga–Zn oxide thin films for oxygen gas sensing  

Microsoft Academic Search

Gallium oxide–zinc oxide (Ga2O3–ZnO) thin films have been prepared by the sol–gel process and their oxygen gas sensing performance has been investigated. These semiconducting films were deposited on alumina substrates with interdigital electrodes and single crystal silicon substrates for the electrical and microstructural characterization. X-ray photoelectron spectroscopy (XPS) showed that the actual concentrations of Ga and Zn thin films differ

A. Trinchi; Y. X. Li; W. Wlodarski; S. Kaciulis; L. Pandolfi; S. P. Russo; J. Duplessis; S. Viticoli

2003-01-01

318

Phase transformation kinetics induced in thin sol-gel PZT films under thermal annealing  

Microsoft Academic Search

The surface morphology evolution and phase transformation kinetics in thin lead zirconate-titanate (PZT) sol-gel films during\\u000a rapid thermal annealing were studied by in situ measurement of scattered light intensity and by recording successive instantaneous optical microscope images. We also studied\\u000a the variation of the texture perfection, the fraction of the growing phase, and the angular dependence of the scattered intensity

V. Ya. Shur; E. B. Blankova; A. L. Subbotin; E. A. Borisova; A. V. Barannikov

2001-01-01

319

Structural and electrochemical studies of Co oxide films formed by the sol-gel technique  

Microsoft Academic Search

Two different types of Co oxide films, each having a distinct electrochemical signature correlated with the film drying temperature, were formed using the sol-gel (SG) technique. Two different states of gelation of the film precursor were also explored. Cyclic voltammograms, collected in alkaline solutions for the low temperature films, displayed two pairs of peaks corresponding to the Co(II) to Co(III)

Anne C. Co; Jingbo Liu; Irina Serebrennikova; Cheryl M. Abel; Viola I. Birss

2005-01-01

320

Critical exponents for sol–gel transition in aqueous alginate solutions induced by cupric cations  

Microsoft Academic Search

The sol–gel transition in aqueous alginate solutions of four alginate samples having different molecular weights (MW) and M\\/G ratios induced by cupric cations was monitored by rheology measurements. The gel point fgel and the relaxation critical exponent n were determined using the Winter’s criterion over the alginate concentration CAlg of 1–4wt%. The scaling for the zero shear viscosity ?0 before

Lu Lu; Xinxing Liu; Zhen Tong

2006-01-01

321

Preparation and characterization of photopolymerizable organic–inorganic hybrid materials by the sol-gel method  

Microsoft Academic Search

A series of UV-curable organic–inorganic hybrid materials were prepared by the sol-gel technique and coated onto Plexiglass® substrate. The effects of the content of EGDMA and the content of the inorganic part on various properties of the coatings,\\u000a such as tensile strength, hardness, gloss, and cross-cut adhesion, were investigated. It was found that the properties of\\u000a the coating were improved

Sevim Karata?; Zuhal Ho?gör; Nilhan-Kayaman Apohan; Atilla Güngör

2010-01-01

322

Electrical properties of high temperature insulation coatings by the sol-gel method for magnet technology  

Microsoft Academic Search

The electrical properties of high temperature insulation coatings, which were applied by sol-gel process on Ag or AgMg sheathed Bi-2212 tapes, bronze processed Nb3Sn wires and Ni tapes, have been studied by resistive, capacitance, and high voltage breakdown techniques. The electrical properties of the coatings with varying composition, coating type, number of dippings, and temperature and time of annealing process

E. Celik; I. H. Mutlu; Y. S. Hascicek

2000-01-01

323

Optical Sol-Gel-Based Dissolved Oxygen Sensor: Progress Towards a Commercial Instrument  

Microsoft Academic Search

A dissolved oxygen sensor based on fluorescence quenching of the oxygen-sensitive ruthenium complex, [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline]2+, which has been immobilized in a porous silica sol-gel-derived film, is reported. Ormosil sensing films were fabricated using modified silica precursors such as methyltriethoxysilane (MTEOS) and ethyltriethoxysilane (ETEOS) and were dip-coated onto planar glass substrates. Tailoring of the films for dissolved oxygen (DO) sensing is described

C. M. Mcdonagh; A. M. Shields; A. K. Mcevoy; B. D. Maccraith; J. F. Gouin

1998-01-01

324

Sol-gel synthesis of colloid and triflates containing hybrid type catalysts  

Microsoft Academic Search

Various colloid and triflate derivatives embedded catalysts were prepared using sol-gel procedure. Ru, Pt and Pd-Au stabilized colloids were embedded in various inorganic matrices like silica, zirconia or silica-tantalum mixed oxide. Mono- or bifunctional catalysts resulted in function of the properties of the matrix support. Lanthanum, silver and tert-butyldimethylsilyl-trifluoromethanesulfonate in supramolecular ensembles with an ammonium-quternary salt were embedded using the

A. N. Pârvulescu; B. C. Gagea; M. Alifanti; V. Pârvulescu

2000-01-01

325

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass  

Microsoft Academic Search

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass\\u000a at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte.\\u000a These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron\\u000a biosensor, pyoverdin

Michael F Yoder; William S Kisaalita

2011-01-01

326

Ceramic thin films by sol-gel processing as novel materials for integrated humidity sensors  

Microsoft Academic Search

Thin films based on 10 at% alkali-doped TiO2 and on iron with very large humidity sensitivity were prepared using a sol-gel technique. Prototype humidity sensors were prepared by depositing metal alkoxide solutions onto Al2O3 substrates with comb-type Au electrodes, by dip-coating and heating in air. Heating to 300°C produces continuous films, free of porosity, which appear as layers covering the

Enrico Traversa; Guglielmina Gnappi; Angelo Montenero; Gualtiero Gusmano

1996-01-01

327

Ultrapure glass optical waveguide: Development in microgravity by the sol gel process  

NASA Technical Reports Server (NTRS)

The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths.

Mukherjee, S. P.; Debsikdar, J. C.; Beam, T.

1983-01-01

328

Photoconductivity on nanocrystalline ZnO\\/TiO2 thin films obtained by sol-gel  

Microsoft Academic Search

In this paper we report results on the synthesis, characterization and photoconductivity behaviour of amorphous and nanocrystalline ZnO\\/TiO2 thin films. They were produced by the sol-gel process at room temperature by using the spin-coating method and deposited on glass substrates. The ZnO\\/TiO2 films were synthesized by using tetrabutyl orthotitanate and zinc nitrate hexahydrate as the inorganic precursors. The samples were

G. Valverde-Aguilar; J. A. García-Macedo; R. Juárez-Arenas

2008-01-01

329

The detection of hexavalent chromium by organically doped sol-gels  

SciTech Connect

The sol-gel process can be used to produce porous inorganic matrices that are doped with organic molecules. These doped gels can be used as a quantitative method for the spectrophotometric determination of trace concentrations of metallic ions. For the detection of hexavalent chromium, malachite green was used as the dopant. Preliminary results indicate concentrations on the order of 5 ppb are detectable using this method.

Wong, P.W.; Mackenzie, J.D. [Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering

1994-12-31

330

Transparent UV curable antistatic hybrid coatings on polycarbonate prepared by the sol–gel method  

Microsoft Academic Search

UV curable, hard, and transparent organic–inorganic hybrid coatings with covalent links between the inorganic and the organic networks were prepared by the sol–gel method. These hybrid coating materials were synthesised using a commercially available, acrylate end-capped polyurethane oligomeric resin, hexanedioldiacrylate (HDDA) as a reactive solvent, 3-(trimethoxysilyl)propoxymethacrylate (MPTMS) as a coupling agent between the organic and inorganic phase, and a metal

M. E. L. Wouters; D. P. Wolfs; M. C. van der Linde; J. H. P. Hovens; A. H. A. Tinnemans

2004-01-01

331

Polymer hybrids of functionalized silsesquioxanes and organic polymers utilizing the sol–gel reaction of tetramethoxysilane  

Microsoft Academic Search

The ternary polymer hybrids were prepared by organic polymers such as poly(2-methyl-2-oxazoline) (POZO) or poly(N-vinylpyrrolidone) (PVP) and aminopropylsilsesquioxane (Cube-aminopropyl) utilizing the sol–gel reaction of tetramethoxysilane (TMOS). The prepared polymer hybrids were characterized by IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), 1H NMR, scanning electron microscopy (SEM), etc. In this hybrid system, hydrogen-bonding interactions played a critical role in the formation

Kyung-Min Kim; Kaoru Adachi; Yoshiki Chujo

2002-01-01

332

Preparation of core shell particles consisting of cobalt ferrite and silica by sol–gel process  

Microsoft Academic Search

Core shell particles consisting of a magnetic core of cobalt ferrite (CoFe2O4) and a shell of silica (SiO2) are prepared by sol–gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of ferrite. The core shell structure is confirmed by TEM. The magnetic properties of these nanocomposites are measured by PPMS in low temperature and

Shuping Zhang; Dawei Dong; Yu Sui; Zhiguo Liu; Hongxia Wang; Zhengnan Qian; Wenhui Su

2006-01-01

333

Carbon nanotube\\/silica composites obtained by sol gel and high-pressure techniques  

Microsoft Academic Search

The successful incorporation of functionalized single-walled carbon nanotubes (f-SWCNTs) into a silica matrix prepared by the sol-gel method is reported herein. SWCNTs produced through catalytic chemical-vapor deposition (CCVD) have been purified and functionalized with sulfuric, nitric and hydrochloric acids to ensure a good dispersion in an aqueous solution. The nanotube composites are prepared using three concentrations of f-SWCNTs (0.025, 0.050

Mônica J. de Andrade; Márcio D. Lima; Carlos P. Bergmann; Guilherme de O. Ramminger; Naira M. Balzaretti; Tania M. H. Costa; Marcia R. Gallas

2008-01-01

334

Carbon nanotube\\/silica composites obtained by sol–gel and high-pressure techniques  

Microsoft Academic Search

The successful incorporation of functionalized single-walled carbon nanotubes (f-SWCNTs) into a silica matrix prepared by the sol–gel method is reported herein. SWCNTs produced through catalytic chemical-vapor deposition (CCVD) have been purified and functionalized with sulfuric, nitric and hydrochloric acids to ensure a good dispersion in an aqueous solution. The nanotube composites are prepared using three concentrations of f-SWCNTs (0.025, 0.050

Mônica J de Andrade; Márcio D Lima; Carlos P Bergmann; Guilherme de O Ramminger; Naira M Balzaretti; Tania M H Costa; Marcia R Gallas

2008-01-01

335

Magnetic Properties of Sodium-Modified Iron-Oxide Powders Synthesized by Sol-Gel Method  

Microsoft Academic Search

Spinel-type ferrites of the sodium-modified iron-oxide (Na-Fe-O) system were synthesized by using a sol-gel method. The maximum magnetic moment of 50 emu\\/g was obtained at the sodium concentration of CNa{=}0.1 to 0.2 (the mol ration of sodium to the sum of sodium and iron), which is about 1.5 times larger than that of non-substituted ones. Monotropic phase transition temperature from

Yasunori Yamanobe; Kazuhiro Yamaguchi; Koji Matsumoto; Toshitaka Fujii

1991-01-01

336

Optical properties and electrochromic characterization of sol–gel deposited ceria films  

Microsoft Academic Search

Ceria (CeO2) films were deposited by the sol–gel spin coating process and optical and electrochromic properties have been investigated. Ceria coating solutions were prepared using cerium amonium nitrate and ethanol. The films were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV–Vis) spectroscopy and cyclic voltammetry. XRD analysis of the films showed that they

Nilgün Özer

2001-01-01

337

Hybrid composite scaffolds prepared by sol–gel method for bone regeneration  

Microsoft Academic Search

This study reports the synthesis and characterization of hydroxyapatite (HA)\\/polycaprolactone (PCL) hybrid composite materials synthesized by sol–gel method. The fabrication of scaffolds was performed by salt-leaching technique using NaCl as porogen agent. In the first step, the physico-chemical characterization of composite material was performed to evaluate the composition and the interaction between the organic\\/inorganic phases. In the second step, optimized

Maria Grazia Raucci; Vincenzo Guarino; Luigi Ambrosio

2010-01-01

338

Optical and electrical properties of transparent conductive ITO thin films deposited by sol–gel process  

Microsoft Academic Search

Indium tin oxide (ITO) thin films have been deposited onto quartz glass substrates by a sol–gel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0–20% by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films

M. J Alam; D. C Cameron

2000-01-01

339

Preparation and properties of electrochromic iridium oxide thin film by sol-gel process  

Microsoft Academic Search

We established a method for preparation of iridium oxide thin film by the sol-gel dip-coating process where iridium chloride was used as a starting material. The coating solution was prepared by reacting iridium chloride, ethanol and acetic acid. Iridium oxide coating was formed at 2.0 cm\\/min withdrawing rate. The coating films heat treated at 300°C did not contain impurities. Iridium

K. Nishio; Y. Watanabe; T. Tsuchiya

1999-01-01

340

The structural and magnetic properties of barium ferrite powders prepared by the sol—gel method  

Microsoft Academic Search

In this paper, M-type hexagonal barium ferrite powders are synthesized using the sol—gel method. A dried precursor heated in air is analyzed in the temperature range from 50 to 1200 °C using thermo-gravimetric analysis and differential scanning calorimetry. The effects of the additives and the cacinating temperature on the magnetic properties are investigated, and the results show that single-phase barium

Li Jie; Zhang Huai-Wu; Li Yuan-Xun; Liu Ying-Li; Ma Yan-Bing

2012-01-01

341

Preparation and characterization of Mg-doped fluorapatite nanopowders by sol–gel method  

Microsoft Academic Search

Properties of hydroxyapatite (HA) or fluorapatite (FA), such as bioactivity, biocompatibility, solubility, and adsorption properties can be tailored over a wide range by modifying the composition via ionic substitutions. This research aimed to prepare and characterize Mg-doped FA (Mg-FA) nanopowders. Mg-FA nanopowders with different Mg contents were prepared by sol–gel method. The designated degree of substitution of Ca2+ by Mg2+

M. Kheradmandfard; M. H. Fathi

2010-01-01

342

Sol–Gel Synthesis of Doped Vitreous Materials with the Use of Modified Aerosils  

Microsoft Academic Search

A novel variant of the sol–gel synthesis of silica glasses and optical composites containing transition-metal ions and nanoparticles is developed. Xerogels and glasses containing 10- to 46-nm particles are prepared with the use of aerosils modified by chromium oxide. The structural and physicochemical properties of chromium oxide–modified silica samples are investigated by X-ray powder diffraction, differential thermal analysis, thermal gravimetric

E. N. Poddenezhnyi; A. A. Boiko; A. A. Alekseenko; N. V. Borisenko; V. M. Bogatyrev

2003-01-01

343

Sol-gel synthesis of rare-earth-doped halide optical materials for photonic applications  

Microsoft Academic Search

Halides have received global attention as potential ultra-low loss optical fiber materials and luminescent sources for all-optical amplification in modern telecommunication systems operating at 1.3 and 1.55 mum. Unfortunately, conventional processing methods currently have failed in their efforts to produce even near-intrinsic material properties. Based on the well- established notion that sol-gel techniques offer high purity, low processing temperature, and

John Michael Ballato

1997-01-01

344

Sol–gel synthesis and properties of multiferroic BiFeO 3  

Microsoft Academic Search

High purity multiferroic BiFeO3 (BFO) powders were synthesized by sol–gel process using bismuth nitrate and iron nitrate as sources. The BFO powders annealed at 600 °C in nitrogen environment were mainly composed of a rhombohedral BiFeO3 phase (R-phase) with a minor impurity phase of Bi2O3. A pure BFO R-phase has been obtained by leaching out the minor Bi2O3 phase using

Jong Kuk Kim; Sang Su Kim; Won-Jeong Kim

2005-01-01

345

E ? ? centers induced by ? irradiation in sol–gel synthesized oxygen deficient amorphous silicon dioxide  

Microsoft Academic Search

The effects of room temperature ?-ray irradiation up to a dose of ?1300kGy are investigated by Electron paramagnetic resonance (EPR) measurements in amorphous silicon dioxide (a-SiO2) produced by a sol–gel synthesis method that introduces OSiSiO oxygen deficiency. We have found that exposure to radiation generates the E?? center with the same spectral features found in high purity commercial a-SiO2. The

S. Agnello; N. Chiodini; A. Paleari; A. Parlato

2007-01-01

346

ITO films on glass substrate by sol–gel technique: synthesis, characterization and optical properties  

Microsoft Academic Search

The present paper extensively demonstrates synthesis, characterization and optical properties of semiconductor indium tin\\u000a oxide (ITO) thin films on glass substrate using sol–gel technique for gas sensor applications. Turbidity, pH values, wettability\\u000a and rheological properties of the prepared solutions were measured to determine solution characteristics by turbidimeter,\\u000a pH meter, contact angle goniometer and rheometer machines prior to coating process. Thermal,

E. Celik; U. Aybarc; M. F. Ebeoglugil; I. Birlik; O. Culha

2009-01-01

347

Titania Thin Films and Supported Nanostructured Membranes Prepared by the Surfactant Assisted Sol-Gel Method  

Microsoft Academic Search

Thin TiO2 nanoparticulate layers were produced by a dip coating of quartz, bo- ron-silicate wafers and of plastic foils. The coating solution was prepared by the sol-gel method in the reverse micelle environment to favour the polycondensation. Reverse mi- celles of a non-ionic surfactant Triton X-100 in cyclohexane were used as the template. The molar ratio water\\/surfactant was kept low

P. Kluson; P. Kacera; T. Cajthaml; M. Kalajic

348

Nafion–zirconia nanocomposite membranes formed via in situ sol–gel process  

Microsoft Academic Search

Crystallized zirconia nanoparticles with diameters of 6.3±0.5nm were in situ formed in Nafion solution through sol–gel process. Nafion molecules were self-assembled onto zirconia nanoparticles through electrostatic interactions and prevent the further growth of initial formed particles. The Nafion–zirconia nanocomposite membranes were formed using a recasting process. It was found that the addition of zirconia nanoparticles did not affect the crystallinity

Jingjing Pan; Haining Zhang; Wei Chen; Mu Pan

2010-01-01

349

Titanium dioxide films for photovoltaic cells derived from a sol–gel process  

Microsoft Academic Search

We present a sol–gel process which is used to prepare thin titanium dioxide nanoparticle layers by spin-coating or doctor-blading techniques. After being sensitized with a dye, the films are used for the transport of electrons in photoelectrochemical solar cells. The titanium dioxide particles have diameters of about 100nm. A comparison with screen-printed layers consisting of particles with a typical size

Yongxiang Li; Jürgen Hagen; Winfried Schaffrath; Peter Otschik; Dietrich Haarer

1999-01-01

350

RBS and NRA of cobalt oxide thin films prepared by the sol-gel process  

Microsoft Academic Search

This work presents a study of cobalt oxide thin films produced by the sol-gel process on aluminum and glass substrates. These films have been analyzed using two ion beam analysis (IBA) techniques: a) a standard RBS 4He 2 MeV and b) nuclear reaction analysis (NRA) using a 1 MeV deuterium beam. The 12C(d,p0)13C nuclear reaction provides information that carbon is

E. Andrade; L. Huerta; E. Barrera; J. C. Pineda; E. P. Zavala; M. F. Rocha; C. A. Vargas

2001-01-01

351

Alcohol sensing properties of sol–gel prepared Sr(II)-added cobalt aluminate spinel composites  

Microsoft Academic Search

Strontium(II)-added CoAl2O4 composites prepared by sol–gel technique were investigated for the sensing properties to alcohols like methanol, ethanol, isopropanol and butanol. X-ray diffraction, scanning electron microscopy and nitrogen adsorption\\/desorption isotherms at 77K were employed to identify the structural phases, surface morphology and BET surface area of the composites, respectively. The composites were prepared with the molar ratios of Co:Sr as

J. Judith Vijaya; L. John Kennedy; G. Sekaran; A. Meenakshisundaram; R. Thinesh Kumar; P. Amalthi; K. S. Nagaraja

2008-01-01

352

ZnS:Mn nanoparticles conjugated to sol–gel-derived silica matrices  

Microsoft Academic Search

Composites from ZnS:Mn nanoparticles and modified silicas are of interest for a broad range of potential applications in the\\u000a form of films, structured particles, and self-assembled structures (e.g., colloidal crystals). They combine the versatility\\u000a of silica sol gel chemistry with the wealth of functionalities available from doped nanoparticulate semiconductors (e.g.,\\u000a optical, electrical, and magnetic). In this work, ZnS:Mn nanoparticles have

Ping Yang; Adam Szatkowski; Michael Bredol

2009-01-01

353

Synthetic implant surfaces. 1. The formation and characterization of sol-gel titania films.  

PubMed

Sol-gel has been used to prepare thin titania films. We have investigated the effects of dip rate, sintering temperature and time on the chemical composition of the films, their physical structure and thickness, and adherence to a silica substrate. Our aim has been to produce films that mimic as closely as possible the natural oxide layer that is found on titanium. These films are to be used as substrates in an in vitro model of osseointegration. PMID:8991481

Haddow, D B; Kothari, S; James, P F; Short, R D; Hatton, P V; van Noort, R

1996-03-01

354

Sol–gel based fabrication of hybrid microfluidic devices composed of PDMS and thermoplastic substrates  

Microsoft Academic Search

Fabrication of microfluidic devices using both rigid and flexible plastic substrates offers benefits for making pressure-actuated membrane valves, mechanically active components, and low-cost but highly functional 3D microchannel networks. Here we present a simple and versatile process for bonding flexible polydimethylsiloxane (PDMS) and rigid thermoplastics like poly(methyl methacrylate) (PMMA), by utilizing the sol–gel method. The silica sol, obtained by oligomerizing

Yusuke Suzuki; Masumi Yamada; Minoru Seki

2010-01-01

355

Synthesis of fluorine doped tin oxide nanoparticles by sol–gel technique and their characterization  

Microsoft Academic Search

This article presents novel attempt to synthesis of fluorine doped tin oxide (FTO) nanoparticles by sol–gel technique. The\\u000a synthesized FTO nanoparticles were obtained after calcination. Temperatures of calcination were 600 and 700 °C due to identify\\u000a changes in the particles size growth. A DG\\/DTA and FTIR study identifies the oxide and formation of the nanopowders. The XRD\\u000a studies confirm the tetragonal

V. Senthilkumar; P. Vickraman; R. Ravikumar

2010-01-01

356

Structural and optical properties of WO 3 electrochromic layers prepared by the sol-gel method  

Microsoft Academic Search

Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel\\u000a method. Compositional, structural and optical characteristics of WO3 coated on indium tin oxide (ITO) conductive glass substrates were studied using X-ray diffractometery (XRD), cyclic voltammetery\\u000a (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline\\u000a structures

Abdoljavad Novinrooz; Masoomeh Sharbatdaran; Hassan Noorkojouri

2005-01-01

357

Sol-gel synthesis of crack-free thin films of calcium lead titanate  

Microsoft Academic Search

Calcium modified lead titanate ferroelectric thin films were prepared using the modification of the diol sol-gel system. The films prepared are crack-free. Single layer films up to ~0.5 ?m thick could be prepared from 0.6 M sols; thicker films up to ~3.5 ?m could be prepared from multiple deposition procedure using ten coating of 0.4 M sol. Firing the precursor

S. Chewasatn; S. J. Milne; N. Pankurddee; L. Chotimongkol

1996-01-01

358

Novel Hybrid Inorganic-Organic Abrasion-Resistant Coatings Prepared by a Sol-Gel Process  

Microsoft Academic Search

Novel abrasion-resistant coatings prepared by a sol-gel process have been developed and applied on the polymeric substrate Bisphenol A polycarbonate. In general, coatings utilize either 4,4?-diaminodiphenyl sulfone (DDS) or diethylenetriamine (DETA) that are then functionalized at their amine groups with 3-isocyanatopropyltriethoxysilane. Following functionalization, these coating materials are then spin coated onto bisphenol A polycarbonate sheet and cured. These reactants undergo

B. Wang; G. L. Wilkes

1994-01-01

359

Abrasion resistant inorganic\\/organic coating materials prepared by the sol-gel method  

Microsoft Academic Search

Novel abrasion resistant coating materials prepared by the sol-gel method have been developed and applied on the polymeric substrates bisphenol-A polycarbonate and diallyl diglycol carbonate resin (CR-39). These coatings are inorganic\\/organic hybrid network materials synthesized from 3-isocyanatopropyltriethoxysilane functionalized organics and metal alkoxide. The organic components are 3,3'-iminobispropylamine (IMPA), resorcinol (RSOL), diethylenetriamine (DETA), poly(ethyleneimine) (PEI), glycerol and a series of diols.

J. Wen; V. J. Vasudevan; G. L. Wilkes

1995-01-01

360

Resistive Switching Characteristics of Sol–Gel Zinc Oxide Films for Flexible Memory Applications  

Microsoft Academic Search

Unipolar resistive switching devices are investigated for nonvolatile memory applications in a metal-insulator-metal structure in which the insulator layer is based on sol-gel-derived zinc oxide (ZnO) films prepared by a simple spin-coating process followed by thermal annealing. Fast programming ( les 50 ns) and a high off-to-on resistance ratio ( ges 104) is demonstrated. The influences on the switching behaviors

Sungho Kim; Hanul Moon; Dipti Gupta; Seunghyup Yoo; Yang-Kyu Choi

2009-01-01

361

Hydrophobicity-induced selective covering of carbon nanotubes with sol–gel sheaths achieved by ultrasound assistance  

Microsoft Academic Search

A simple construction of sol–gel sheaths onto the surface of multi-walled carbon nanotubes (MWCNTs) has been carried out in water by a hydrophobicity-induced covering with the assistance of ultrasound. The ultrasound assistance prevents in water an unregulated agglomeration induced by the hydrophobicity of MWCNTs and phenyl-containing sols, leading to a selective construction of sol–gel sheaths on the nanotube surface. The

Ki Chul Park; Tomoaki Mahiko; Shingo Morimoto; Kenji Takeuchi; Morinobu Endo

2008-01-01

362

Development and characterization of a family of shape memory, biocompatible, degradable, porous (co)-polyurethanes via sol-gel chemistry  

Microsoft Academic Search

In support of the goal of a tissue engineering scaffold that is moldable, biodegradable and has shape-memory, this work explored the space of polyurethane sol-gel formulations and solvents to create a biocompatible, porous xerogel with potential to be such a porous scaffold. The work has resulted in both a process and a sol-gel formulation to effectively create a family of

Hugh Walker Lippincott

2010-01-01

363

Sol-gel optical thin films for an advanced megajoule-class Nd:glass laser ICF driver  

Microsoft Academic Search

It is well established by manufacturers and users that optical coatings are generally prepared by the well known physical vapor deposition (PVD) technology. In the authors' opinion sol-gel technology is an effective and competitive alternative. The aim of this paper is to emphasize the sol-gel thin film work carried out at Centre d'Etudes de Limeil-Valenton (CEL-V) and concerning the technology

Herve G. Floch; Phillippe F. Belleville; Philippe M. Pegon; Corinne S. Dijonneau; Jacques R. Guerain

1995-01-01

364

Selective formation of isobutane and isobutene from synthesis gas over zirconia catalysts prepared by a modified sol-gel method  

Microsoft Academic Search

Zirconium oxide was synthesized by a modified sol-gel method, and was evaluated for the selective formation of isobutane and isobutene from synthesis gas. Due to increased basicity, zirconia from sol-gel preparation showed higher selectivities to iso-C[sub 4]'s while maintaining the same level of activity as zirconia prepared by calcination of zirconyl salts. The catalysts was further modified with Group I

Z. Feng; W. S. Postula; C. Erkey; C. V. Philip; A. Akgerman; R. G. Anthony

1994-01-01

365

A new method for fabricating water repellent silica films having high heat-resistance using the sol–gel method  

Microsoft Academic Search

There has been a great demand in the field of kitchen appliances to develop transparent water repellent films which have high heat-resistance around 300°C. However, those films have not been obtained by conventional sol–gel methods. In this paper, we propose a new method for fabricating transparent water repellent films with high heat-resistance using the sol–gel method, in which silicon or

Tohru Nakagawa; Mamoru Soga

1999-01-01

366

Surface characterization of sol-gel derived scintillating rare-earth doped Lu2SiO5 thin films  

E-print Network

Surface characterization of sol-gel derived scintillating rare- earth doped Lu2SiO5 thin films C-marie.nedelec@univ-bpclermont.fr Abstract. Rare earth doped Lu2SiO5 thin films have been prepared by combining sol-gel process and spin of rare earth doping ions. XPS and RBS spectrocopies showed that the composition of the films is close

Paris-Sud XI, Université de

367

Sol–gel-derived amperometric biosensor for hydrogen peroxide based on methylene green incorporated in Nafion film  

Microsoft Academic Search

A hydrogen peroxide biosensor was fabricated by coating a sol–gel–peroxidase layer onto a Nafion-methylene green modified electrode. Immobilization of methylene green (MG) was attributed to the electrostatic force between MG+ and the negatively charged sulfonic acid groups in Nafion polymer, whereas immobilization of horseradish peroxidase was attributed to the encapsulation function of the silica sol–gel network. Cyclic voltammetry and chronoamperometry

Bingquan Wang; Shaojun Dong

2000-01-01

368

Anatase TiO 2 porous thin films prepared by sol-gel method using CTAB surfactant  

Microsoft Academic Search

Anatase TiO2 porous thin films were prepared on glass substrates by sol-gel method with Cetyltrimethylammonium Bromide (CTAB) as a pore-forming\\u000a agent, Tetrabutylorthotitanate as Ti precursor, ethanol as solvent and diethanolamine as chelating agent respectively. IR,\\u000a TG-DSC, XRD and SEM analyzed the chemical and physical changes during sol-gel process and characteristics of the films. Effects\\u000a of the amount of CTAB, alkane

G. Q. Liu; Z. G. Jin; X. X. Liu; T. Wang; Z. F. Liu

2007-01-01

369

Hydrophobicity-induced selective covering of carbon nanotubes with sol gel sheaths achieved by ultrasound assistance  

NASA Astrophysics Data System (ADS)

A simple construction of sol-gel sheaths onto the surface of multi-walled carbon nanotubes (MWCNTs) has been carried out in water by a hydrophobicity-induced covering with the assistance of ultrasound. The ultrasound assistance prevents in water an unregulated agglomeration induced by the hydrophobicity of MWCNTs and phenyl-containing sols, leading to a selective construction of sol-gel sheaths on the nanotube surface. The phenyl groups of the resulting sol-gel sheaths were successfully removed by air-oxidation to provide the MWCNTs covered with amorphous SiO 2 sheaths. The effect of the SiO 2 sheaths on the electrical and thermal properties of the SiO 2-MWCNT nanocomposites was evaluated from the electrical resistivities of the nanocomposites with two different SiO 2 concentrations and the thermal conductivities of their phenol-resin composites. The results indicate that the small increase of the SiO 2 concentration remarkably increases the electrical resistivity of the SiO 2-MWCNT nanocomposites. Furthermore, the SiO 2 sheaths have more directly influenced the thermal property of the polymer composites than the inside nanotubes.

Park, Ki Chul; Mahiko, Tomoaki; Morimoto, Shingo; Takeuchi, Kenji; Endo, Morinobu

2008-09-01

370

Thin-film silica sol-gels doped with ion responsive fluorescent lipid bilayers  

SciTech Connect

A metal ion sensitive, fluorescent lipid-b i layer material (5oA PSIDA/DSPC) was successfully immobilized in a silica matrix using a tetramethoxysilane (TMOS) sol-gel procedure. The sol-gel immobilization method was quantitative in the entrapment of seif-assembled Iipid-bilayers and yielded thin films for facile configuration to optical fiber piatforms. The silica matrix was compatible with the solvent sensitive lipid bilayers and provided physical stabilization as well as biological protection. Immobilization in the silica sol-gel produced an added benefit of improving the bilayer's metal ion sensitivity by up to two orders of magnitude. This enhanced performance was attributed to a preconcentrator effect from the anionic surface of the silica matrix. Thin gels (193 micron thickness) were coupled to a bifurcated fiber optic bundle to produce a metal ion sensor probe. Response times of 10 - 15 minutes to 0.1 M CUCIZ were realized with complete regeneration of the sensor using an ethylenediarninetetraacetic acid (EDTA) solution.

Sasaki, D.Y.; Shea, L.E.; Sinclair, M.B.

1999-01-12

371

Direct test of the critical exponents at the sol-gel transition  

NASA Astrophysics Data System (ADS)

The steady state fluorescence technique was used to study the sol-gel transition for the solution-free radical cross-linking polymerization of acrylamide (AAm), with N,N'-methylenebis (acrylamide) as cross linker in the presence of ammonium persulfate as an initiator. Pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt) is used as a fluoroprobe for monitoring the polymerization. Pyranine molecules start to bind to acrylamide polymer chains upon the initiation of the polymerization, thus the spectra of the bonded pyranines shift to the shorter wavelengths. Fluorescence spectra from the bonded pyranines allows one to monitor the sol-gel transition, without disturbing the system mechanically, and to test the universality of the sol-gel transition as a function of some kinetic parameters such as polymer concentration, cross-linker concentration, and temperature. Observations around the critical point show that there are three regimes for AAm concentration in which the exponents differ drastically. The gel fraction exponent ? and the weight average degree of polymerization exponent ? agree best with the static percolation results for higher acrylamide concentrations above 1M, but they cross over from percolation to mean-field (Flory-Stockmayer) values when the AAm concentration is lower than 2M. For very low polymer concentrations, below which the system can not form the gel, the exponents differ considerably from both the percolation and the mean-field values.

Kaya, Demet; Pekcan, Önder; Y?lmaz, Ya?ar

2004-01-01

372

Development of electrochemical biosensors based on sol-gel enzyme encapsulation and protective polymer membranes.  

PubMed

Protective polymer coatings have been used to enhance the retention of enzymes in sol-gel films as immobilisation phases in electrochemical biosensors. Carbon film electrodes were electrochemically modified with poly(neutral red) (PNR). These electrodes were coated with oxysilane sol-gels incorporating glucose oxidase and an outer coating of carboxylated PVC (CPVC) or polyurethane (PU), with and without Aliquat-336 or isopropyl myristate (IPM) plasticizer, was applied. The biosensors were characterised electrochemically using cyclic voltammetry and amperometry, electrochemical impedance spectroscopy and scanning electron microscopy. Impedance spectra showed that the electrode surface is most active when the sol-gel-GOx layer is not covered with a membrane. However, membranes without plasticizer extend the lifetime of the biosensor to more than 2 months when PU is used as an outer membrane. The linear range of the biosensors was found to be 0.05-0.50 mM of glucose and the biosensor with PU outer membrane exhibited higher sensitivity (ca.117 nA mM(-1)) in the region of linear response than that with CPVC. The biosensors were applied to glucose measurement in natural samples of commercial orange juice. PMID:18080811

Pauliukaite, Rasa; Schoenleber, Monika; Vadgama, Pankaj; Brett, Christopher M A

2008-02-01

373

Sol-gel chemistry in biosensing devices of electrical transduction: application to CEA cancer biomarker.  

PubMed

Sol-gel chemistry allows the immobilization of organic molecules of biological origin on suibtable solid supports, permitting their integration into biosensing devices widening the possibility of local applications. The present work is an application of this principle, where the link between electrical receptor platform and the antibody acting as biorecognition element is made by sol-gel chemistry. The immunosensor design was targeted for carcinoembryonic antigen (CEA), an important biomarker for screening the colorectal cancer, by electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SVW). The device displayed linear behavior to CEA in EIS and in SWV assays ranging from 0.50 to 1.5ng/mL, and 0.25 to 1.5ng/mL, respectively. The corresponding detection limits were 0.42 and 0.043 ng/mL. Raman spectroscopy was used to characterize the surface modifications on the conductive platform (FTO glass). Overall, simple sol-gel chemistry was effective at the biosensing design and the presented approach can be a potential method for screening CEA in point-of-care, due to the simplicity of fabrication, short response time and low cost. PMID:25547969

Truta, Liliana A A N A; Sales, M Goreti F

2015-01-01

374

Sealing of pores in sol-gel-derived tritium permeation barrier coating by electrochemical technique  

NASA Astrophysics Data System (ADS)

An electrolytic deposition technique was applied to seal open pores in sol-gel derived ZrO 2 coating and to improve barrier effects against permeation of hydrogen isotopes. Disk-type specimens of type 430 ferritic stainless steel were first covered by thin ZrO 2 films (50 nm) with a conventional sol-gel technique. Then, pores in the ZrO 2 film was sealed with ZrO 2 or Al 2O 3 by cathodic processes in ethanol solution of Zr or Al nitrate and subsequent heat treatments in air. The permeation rate of hydrogen was measured at 300-600 °C. The sol-gel derived ZrO 2 coatings showed only limited barrier effects; the permeation reduction factor (PRF) was about 6-800. Nevertheless, the treatments by electrolytic deposition technique resulted in considerable improvement in the barrier effects, especially at high temperature region (>500 °C), and the PRF increased to 100-1000.

Zhang, Kun; Hatano, Yuji

2011-10-01

375

Preparation and Characterization of Sol-Gel TiO2/ITO Photoelectrodes  

NASA Astrophysics Data System (ADS)

In this work, nanocrystalline TiO2/ITO electrodes were prepared by sol-gel method starting from tetrabutyl orthotitanate (Ti(OBun)4) reacted with hydrogen peroxide in the ice-water bath. The sol-gel derived TiO2 films were characterized by XRD, SEM, BET, and UV/Vis absorption spectroscopic techniques. The preparation conditions, including the number of coats and calcination temperature, were also investigated. Furthermore, PEC cells were constructed for testing the activities of prepared TiO2/ITO photoelectrodes. The photo-currents for hydrogen production via the PEC reaction were measured under UV irradiation (?max = 253.7 nm). The experimental results showed that the sol-gel derived TiO2 films calcined at 300°C-600°C were anatase structure and they showed a maximum UV/Vis absorption at about 380 nm. Moreover, from the result of PEC reactions, it was found that the TiO2/ITO photoelectrode (calcined at 600°C, with the thickness of TiO2 layer of about ~0.2 ?m) demonstrated a large saturation current (0.326 mA/cm2) with a quite high photoelectrochemical conversion efficiency of 2.39%.

Liang, Chia-Hung; Chang, Hung-Yi; Liou, Tsz-Wei; Chen, Huey-Ing

376

Synthesis of garnet structure compounds using aqueous sol-gel processing  

NASA Astrophysics Data System (ADS)

The sol-gel method based on metal chelates in aqueous solvents has been developed to prepare different oxides having garnet crystal structure. This synthetic approach has been used to prepare rare-earth doped yttrium aluminum garnet Y 3Al 5O 12:Ce, Y 3Al 5O 12:Nd, Y 3Al 5O 12:Ho, and Y 3Al 5O 12:Er samples (YAG:Ln). The polycrystalline powders sintered at 1000 °C are formed as single-phase garnet materials. The formation of pure and neodymium-doped lanthanum aluminum garnets (La 3Al 5O 12 (LAG), and La 3Al 5O 12:Nd (LAG:Nd)) at the same synthesis conditions, however, does not proceed. A systematic study of sol-gel technique synthesized Y 3Ga 5O 12 (YGG) is presented using six different complexing agents. These complexing agents were found to influence the characteristics of the end products, in particular the homogeneity. Finally, some specific features of sol-gel derived mixed-metal Y 3Sc xAl 5- x- yGa yO 12 (0? x, y?5) (YSAGG) garnets are discussed in the present paper. The phase purity, composition and microstructural features in the polycrystalline samples were studied by XRD analysis, IR spectroscopy and scanning electron microscopy.

Leleckaite, A.; Kareiva, A.

2004-07-01

377

MOS solar cells with oxides deposited by sol-gel spin-coating techniques  

SciTech Connect

The metal-oxide-semiconductor (MOS) solar cells with sol-gel derived silicon dioxides (SiO{sub 2}) deposited by spin coating are proposed in this study. The sol-gel derived SiO{sub 2} layer is prepared at low temperature of 450 Degree-Sign C. Such processes are simple and low-cost. These techniques are, therefore, useful for largescale and large-amount manufacturing in MOS solar cells. It is observed that the short-circuit current (I{sub sc}) of 2.48 mA, the open-circuit voltage (V{sub os}) of 0.44 V, the fill factor (FF) of 0.46 and the conversion efficiency ({eta}%) of 2.01% were obtained by means of the current-voltage (I-V) measurements under AM 1.5 (100 mW/cm{sup 2}) irradiance at 25 Degree-Sign C in the MOS solar cell with sol-gel derived SiO{sub 2}.

Huang, Chia-Hong, E-mail: chhuang@nknu.edu.tw [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China); Chang, Chung-Cheng [National Taiwan Ocean University, Department of Electrical Engineering, Taiwan (China); Tsai, Jung-Hui [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China)

2013-06-15

378

Transparent conductive CuFeO2 thin films prepared by sol-gel processing  

NASA Astrophysics Data System (ADS)

In this study, transparent conductive CuFeO2 thin films were deposited onto a quartz substrate using a low-cost sol-gel process and sequential annealing in N2. The sol-gel derived films were annealed at 500 °C for 1 h in air and then annealed at 700 °C in N2 for 2 h. The CuO and CuFe2O4 phases appeared as the film annealed in air, and a single CuFeO2 phase (delafossite, R3m) appeared as the film annealed in N2. X-ray photoelectron spectroscopy showed that the chemical composition of the CuFeO2 thin films was similar to the stoichiometry. The optical bandgap of the CuFeO2 thin films was 3.1 eV. The p-type characteristics of the films were verified by Hall-effect measurements. The electrical conductivity and carrier concentration of the CuFeO2 thin films were 0.358 S cm-1 and 5.34 × 1018 cm-3, respectively. These results show that the proposed low-cost sol-gel process provides a feasible method of depositing transparent CuFeO2 thin films.

Chen, Hong-Ying; Wu, Jia-Hao

2012-03-01

379

Preparation and characterisation of a sol-gel process ?-Al?O? polycrystalline detector.  

PubMed

This article presents the dosimetric characteristics of ?-Al2O3 detectors prepared through the sol-gel process, disc pressing and sintering in a highly reducing atmosphere. Comparative tests between the sol-gel process ?-Al2O3 polycrystalline and anion-defective ?-Al2O3:C single-crystal detectors indicate that the ones prepared through this approach present good dosimetric characteristics similar to those found in single-crystal detectors, such as a simple glow curve with the main peak at ?198 °C (2 °C s(-1)), high sensitivity, a detection threshold of 1.7 µGy, linearity of response, low fading, relatively low photon energy dependence, reusability without annealing and good reproducibility. However, the undesirable feature of heating rate dependence of the thermoluminescence (TL) output in ?-Al2O3:C single crystal is practically non-existent in the sol-gel process ?-Al2O3 polycrystalline detector. This characteristic renders it useful for the routine processing of large numbers of personal and environmental dosemeters at higher heating rates and also when it comes to the proposal for new approaches to thermal quenching investigation. PMID:24795396

Ferreira, H R; Santos, A

2015-02-01

380

Formation and prevention of fractures in sol-gel-derived thin films.  

PubMed

Sol-gel-derived thin films play an important role as the functional coatings for various applications that require crack-free films to fully function. However, the fast drying process of a standard sol-gel coating often induces mechanical stresses, which may fracture the thin films. An experimental study on the crack formation in sol-gel-derived silica and organosilica ultrathin (submicron) films is presented. The relationships among the crack density, inter-crack spacing, and film thickness were investigated by combining direct micrograph analysis with spectroscopic ellipsometry. It is found that silica thin films are more prone to fracturing than organosilica films and have a critical film thickness of 300 nm, above which the film fractures. In contrast, the organosilica films can be formed without cracks in the experimentally explored regime of film thickness up to at least 1250 nm. These results confirm that ultrathin organosilica coatings are a robust silica substitute for a wide range of applications. PMID:25466584

Kappert, Emiel J; Pavlenko, Denys; Malzbender, Jürgen; Nijmeijer, Arian; Benes, Nieck E; Tsai, Peichun Amy

2015-02-01

381

Sol gel ZnO films doped with Mg and Li evaluated for charged particle detectors  

NASA Astrophysics Data System (ADS)

In this work we assess the feasibility of ZnO films deposited from a sol gel precursor as a material for thin film charged particle detectors. There are many reports of polycrystalline ZnO thin film transistors (TFTs) in the literature, deposited by sputtering, pulsed laser deposition, and sol gel. There are also reports of sol gel derived ZnO doped with Li or Mg to increase the resistivity, however, these works only measure resistivity of the films, without determining the effect of doping on the carrier concentration. We study the effects of doping the ZnO with Mg and Li as well as the effects of thickness on the films' resistivity, mobility, and carrier concentration, since these material parameters are critical for a charged particle sensor. Carrier concentration is particularly important because it must be kept low in order for the intrinsic region of a p-i-n diode to be depleted. In order to accomplish this we fabricate and electrically characterize test structures for resistivity, test structures for hall measurement, common back-gate TFTs, and metal-insulator-semiconductor (MIS) capacitors. We also conduct physical characterization techniques such as x-ray diffraction (XRD), atomic force microscopy (AFM), electron microscopy, UV-Vis spectroscopy, and ellipsometry to determine the effect of doping and film thickness on the microstructure and optical properties of the ZnO.

Murphy, John W.; Eddy, Alexander; Kunnen, George R.; Mejia, Israel; Cantley, Kurtis D.; Allee, David R.; Quevedo-Lopez, Manuel A.; Gnade, Bruce E.

2013-05-01

382

Effect of the concentration on sol-gel transition of telechelic polyelectrolytes.  

PubMed

Telechelic polyelectrolytes, bearing short hydrophobic blocks at both ends, will ionize into polyions and their counterions when dissolved in water. With the variation of concentration, the interplay between short range attraction and the long range electrostatic interaction as well as the counterion distribution exerts a major influence on the chain conformations (two basic conformations: loop and nonloop, the latter can be subdivided into three association types: free, dangling, and bridge), the cluster structure and the forming of a physical gel. For weak hydrophobic interaction, the relative strong electrostatic interaction dominates the gelation progress; sol-gel transition occurs at higher concentrations due to electrostatic screening and mainly involves the forming of stretched nonloop conformations such as dangling and bridge. While for strong hydrophobic interaction, the hydrophobic interaction dominates and the electrostatic interaction provides a contribution to the formation of gels by maintaining a spatial swelling structure, resulting in a much lower concentration region of sol-gel transition; besides, the sol-gel transition is characterized by the competition of the forming of loop and bridge chains. PMID:21261387

Zhang, Ran; Shi, Tongfei; Li, Hongfei; An, Lijia

2011-01-21

383

Chemical sensing using sol-gel derived planar waveguides and indicator phases  

SciTech Connect

A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW). The upper layer is an undensified glass of lower index doped with an optical indicator that is immobilized, yet remains sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb{sup 2+} and pH, based on immobilized xylenol orange and bromocresol purple, respectively. The response of both sensors was sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries. 48 refs., 8 figs.

Yang, L.; Saavedra, S.S. [Univ. of Arizona, Tucson, AZ (United States)

1995-04-15

384

Fabrication and characterization of sol-gel based nanoparticles for drug delivery  

NASA Astrophysics Data System (ADS)

Nanogels are cross linked polymeric sol-gel based nanoparticles that offer an interior network for incorporation and protection of biomolecules, exhibiting unique advantages for polymer based delivery systems. We have successfully synthesized stable sol-gel nanoparticles by means of [a] silicification reactions using cationic peptides like polylysine as gelating agents, and [b] lyophilization of sol-gels. Macromolecules such as Hemoglobin and Glucose Oxidase and small molecules such as Sodium Nitroprusside (SNP) and antibiotics were encapsulated within the nanogels. We have used transmission electron microscopy, dynamic light scattering, zeta potential analysis, and spectroscopy to perform a physicochemical characterization of the nanogels resulting from the two approaches. Our studies have indicated that the nanogel encapsulated proteins and small molecules remain intact, stable and functional. A Hydrogen Peroxide (H2O2) and Nitric Oxide (NO) generating drug carrier was synthesized using these nanogels and the effect of generation of H2O2 from Glucose Oxidase encapsulated nanogels and NO from SNP encapsulated nanogels was tested on E.coli. The results show that the nanoparticles exert antimicrobial activity against E.Coli, in addition NO generating nanogels potentiated H2O2 generating nanogels induced killing. These data suggest that these NO and H2O2 releasing nanogels have the potential to serve as a novel class of antimicrobials for the treatment of multidrug resistant bacteria. The unique properties of these protein/drug incorporated nanogels raise the prospect of fine tailoring to specific applications such as drug delivery and bio imaging.

Yadav, Reeta

385

Microstructural characterization of sol-gel lead-zirconate-titanate thin films  

NASA Astrophysics Data System (ADS)

The techniques of x-ray diffraction, x-ray photoelectron spectroscopy (XPS), Auger analysis, and transmission and scanning transmission electron microscopy (TEM) have been applied to the analysis of thin films of Pb(Zr0.30Ti0.70)O3 (PZT30/70) deposited at low temperatures (510 °C) by a sol-gel process onto Pt/Ti electrodes on SiO2/Si 100 substrates. It is found that the platinum film is highly oriented with the [111] axis perpendicular to the substrate plane. The ferroelectric film tends to crystallize epitaxially upon this as columnar crystals. There are indications from the TEM of the existence of a second metallic phase at the interface between the platinum and the PZT30/70 film, which may be associated with its nucleation. The TEM shows the boundaries between the individual sol-gel layers, although the growing crystallites of the PZT30/70 propagate through these boundaries unhindered. The XPS and Auger analyses have shown that Pb penetrates through the Pt layer to the underlying Ti layer, even at the low crystallization temperatures used. There is also clear evidence for diffusion of the Zr and Ti prior to, or during the crystallization process, so that the Zr migrates to the surface of each sol-gel layer. The effects of using different crystallization processes on this compositional separation and the reasons for its occurrence are discussed, as are the possible effects upon macroscopically measured ferroelectric properties.

Impey, S. A.; Huang, Z.; Patel, A.; Beanland, R.; Shorrocks, N. M.; Watton, R.; Whatmore, R. W.

1998-02-01

386

Hybrid sol-gel gratings for optical and non linear optical applications  

NASA Astrophysics Data System (ADS)

Free-radical photocurable hybrid material was used for the creation of crack free holographic gratings, showing only a refractive index modulation. Organic-inorganic materials based on the sol-gel synthesis of alkoxysilanes have demonstrated their great potential for coating and optical applications. In a first step, hydrolysis and condensation reactions were led under mild conditions along the same way as in classical sol-gel glasses. Partial elaboration of the silicate backbone was thus achieved. Then, with the use of a photoinitiator, free-radical polymerization was proceeded by irradiating the material under UV or visible light. A spatially controlled photopatterning can be thus achieved to create optical elements having the hardness of a glass-like material. The presented results concern the formation of gratings created by transmission using interference pattern at 514 nm. Diffraction efficiencies up to 90 % were reached for 1000 lines/mm in transmission, corresponding to a refractive index modulation amplitude of 4.10-3 (according to the Kogelnik's theory). To elaborate non linear quadratic optical devices, hybrid sol-gel matrixes were doped with push-pull chromophores. Such a photosensitive system enables simultaneous photopatterning of the layer and poling of the NLO molecules. Experiments were realized during the photopolymerization step, in order to study the freezing of the non-centrosymetric orientation of the dispersed NLO chromophores.

Croutxe-Barghorn, C.; Feuillade, M.; Carre, C.; Mager, Loic; Fort, Alain

2005-06-01

387

Growth of lead zirconate titanate thin films by hybrid processing: sol gel method and pulsed-laser deposition  

NASA Astrophysics Data System (ADS)

Lead zirconate titanate (Pb(Zr xTi 1- x)O 3: PZT) thin films were prepared on Pt/Ti/SiO 2/Si substrates by hybrid processing: sol-gel method and pulsed-laser deposition (PLD). X-ray diffraction analysis indicated that the PZT films mainly had a perovskite-type structure with (1 0 0)-preferred orientation, and no peak corresponding to pyrochlore was detected. The transmission electron microscopy image showed that the films had a polycrystalline columnar microstructure extending through the thickness of the film, and no sharp interface was observed between the layers obtained by the sol-gel method and PLD. The HTEM image also revealed that the crystalline lattice of the layers was continuous and there was no difference in crystalline orientation between the layers obtained by the sol-gel method and PLD. These results indicated that the lower PZT layer deposited by the sol-gel method acted as a seed layer for the crystallization of the upper PZT layer deposited by PLD. The solid-phase epitaxial effect between the PZT layers deposited by the sol-gel method and PLD lowers the temperature of postdeposition annealing, and the preferred orientation of the PZT films can be controlled using the layer deposited by the sol-gel method.

Wang, Zhan Jie; Kokawa, Hiroyuki; Maeda, Ryutaro

2004-02-01

388

Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO{sub 3}  

SciTech Connect

Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of La{sub x}Bi{sub 1-x}FeO{sub 3} (LBFO) ceramics (0 {<=} x {<=} 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO{sub 3} (BFO) for x {<=} 0.2 but transforms to orthorhombic Pbnm structure for x > 0.2. The fundamental 12 Raman modes of pure BFO (x = 0.0) are reduced to 10 modes for x = 0.2 and further reduced to 7 modes for x = 0.4, which is a clear indication of structural modification and symmetry changes brought about by La doping. The coercive field, H{sub C}, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest H{sub C} (19.5 kOe at RT) reported so far in any rare earth doped BFO, which will have a great potential for practical application in non-volatile memory devices. Moreover, high-field magnetization and remanence, M{sub r}, increase linearly with La doping content due to the gradual change in spin cycloid structure. M(T) curve shows an anomaly at 50 K, similar to that expected in a spin glass system. The Neel temperature (T{sub N}) of the LBFO increases with x, approaching that of the LaFeO{sub 3}.

Suresh, Pittala; Srinath, S. [School of Physics, University of Hyderabad, Gachibowli, Hyderabad 500 046 (India)

2013-05-07

389

Sol-gel preparation of alumina stabilized rare earth areo- and xerogels and their use as oxidation catalysts.  

PubMed

A new sol-gel synthesis route for rare earth (Ce and Pr) alumina hybrid aero- and xerogels is presented which is based on the so-called epoxide addition method. The resulting materials are characterized by TEM, XRD and nitrogen adsorption. The results reveal a different crystallization behavior for the praseodymia/alumina and the ceria/alumina gel. Whereas the first remains amorphous until 875°C, small ceria domains form already after preparation in the second case which grow with increasing calcination temperature. The use of the calcined gels as CO oxidation catalysts was studied in a quartz tube (lab) reactor and in a (slit) microreactor and compared to reference catalysts consisting of the pure rare earth oxides. The Ce/Al hybrid gels exhibit a good catalytic activity and a thermal stability against sintering which was superior to the investigated reference catalyst. In contrast, the Pr/Al hybrid gels show lower CO oxidation activity which, due to the formation of PrAlO3, decreased with increasing calcination temperature. PMID:24655831

Neumann, Björn; Gesing, Thorsten M; Rednyk, Andrii; Matolin, Vladimir; Gash, Alexander E; Bäumer, Marcus

2014-05-15

390

Remediation of waters contaminated with MCPA by the yeasts Lipomyces starkeyi entrapped in a sol-gel zirconia matrix.  

PubMed

A single-stage sol-gel route was set to entrap yeast cells of Lipomyces starkeyi in a zirconia (ZrO(2)) matrix, and the remediation ability of the resulting catalyst toward a phenoxy acid herbicide, 4-chloro-2-methylphenoxyacetic acid (MCPA), was studied. It was found that the experimental procedure allowed a high dispersion of the microorganisms into the zirconia gel matrix; the ZrO(2) matrix exhibited a significant sorption capacity of the herbicide, and the entrapped cells showed a degradative activity toward MCPA. The combination of these effects leads to a nearly total removal efficiency (>97%) of the herbicide at 30 °C within 1 h incubation time from a solution containing a very high concentration of MCPA (200 mg L(-1)). On the basis of the experimental evidence, a removal mechanism was proposed involving in the first step the sorption of the herbicide molecules on the ZrO(2) matrix, followed by the microbial degradation operated by the entrapped yeasts, the metabolic activity of which appear enhanced under the microenvironmental conditions established within the zirconia matrix. Repeated batch tests of sorption/degradation of entrapped Lipomyces showed that the removal efficiency retained almost the same value of 97.3% after 3 batch tests, with only a subsequent slight decrease, probably due to the progressive saturation of the zirconia matrix. PMID:21077667

Sannino, Filomena; Pirozzi, Domenico; Aronne, Antonio; Fanelli, Esther; Spaccini, Riccardo; Yousuf, Abu; Pernice, Pasquale

2010-12-15

391

Sol-gel analogous aminolysis-ammonolysis of chlorosilanes to chlorine-free Si/(C)/N-materials.  

PubMed

Large amounts of chlorosilanes, especially SiCl4 and CH3SiCl3, are produced as side-products of the industrial fabrication of solar or electronic grade silicon and the Müller-Rochow process. It was a goal of the present study to transform these compounds into useful chlorine-free precursors for Si/(C)/N ceramics via a sol-gel analogous liquid processing route. Chlorine substitution of the chlorosilanes (mixtures) with diethylamine did not yield chlorine-free products, complete reactions are only possible with lithium diethylamide. However, aminolyses with n-propylamine were successful. Transamination with ammonia was not possible with diethylaminosilanes but was with n-propylaminosilanes in various solvents. This result was attributed to steric reasons and polar interactions of the N-H groups. Colourless solid or liquid polysilazanes were obtained, depending on the silane (mixture) and the solvent. Transamination reactions of CH3Si(NH-n-Pr)3 in chloroform reproducibly yielded a cage-like oligosilazane of the composition (CH3)9Si9(NH)12N. Single crystal X-ray structure analysis revealed a seven-cyclic cluster containing four six- and three ten-membered silazane rings. This unique silazane cage as well as the other aminosilanes and the silazanes were comprehensively characterised using multi-nuclear solid state and solution NMR, elemental analyses and thermal gravimetry (TGA). PMID:19587990

Wiltzsch, Conny; Wagler, Jörg; Roewer, Gerhard; Kroke, Edwin

2009-07-28

392

Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO3  

NASA Astrophysics Data System (ADS)

Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of LaxBi1-xFeO3 (LBFO) ceramics (0 ? x ? 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO3 (BFO) for x ? 0.2 but transforms to orthorhombic Pbnm structure for x > 0.2. The fundamental 12 Raman modes of pure BFO (x = 0.0) are reduced to 10 modes for x = 0.2 and further reduced to 7 modes for x = 0.4, which is a clear indication of structural modification and symmetry changes brought about by La doping. The coercive field, HC, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest HC (19.5 kOe at RT) reported so far in any rare earth doped BFO, which will have a great potential for practical application in non-volatile memory devices. Moreover, high-field magnetization and remanence, Mr, increase linearly with La doping content due to the gradual change in spin cycloid structure. M(T) curve shows an anomaly at 50 K, similar to that expected in a spin glass system. The Néel temperature (TN) of the LBFO increases with x, approaching that of the LaFeO3.

Suresh, Pittala; Srinath, S.

2013-05-01

393

A new sol-gel synthesis of 45S5 bioactive glass using an organic acid as catalyst.  

PubMed

In this paper a new sol-gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol-gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol-gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2M nitric acid solution or either a 5mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer-Emmett-Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol-gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol-gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol-gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol-gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. PMID:25492213

Faure, J; Drevet, R; Lemelle, A; Ben Jaber, N; Tara, A; El Btaouri, H; Benhayoune, H

2015-02-01

394

Development of a fiber optic dissolved oxygen sensor based on quenching of a ruthenium complex entrapped in a porous sol-gel film  

Microsoft Academic Search

A dissolved oxygen sensor, based on sol-gel-derived silica thin films impregnated with an oxygen-sensitive ruthenium complex, is reported. Porous sol-gel silica films, dipcoated onto either planar glass substrates or declad optical fibers, are doped with the complex [RuII-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence emission is quenched by oxygen. The complex is entrapped in the cage-like structure of the sol-gel matrix, but is accessible

Aisling K. McEvoy; Colette M. McDonagh; Brian D. MacCraith

1995-01-01

395

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material  

DOEpatents

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

Panitz, Janda K. (Sandia Park, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Moffatt, William C. (Albuquerque, NM)

1999-01-01

396

Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material  

DOEpatents

Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties. 6 figs.

Panitz, J.K.; Reed, S.T.; Ashley, C.S.; Neiser, R.A.; Moffatt, W.C.

1999-07-20

397

Enhanced piezoelectric properties of lead zirconate titanate (PZT) sol-gel derived ceramics using single crystal PZT cubes  

NASA Astrophysics Data System (ADS)

Piezoceramic materials have attracted much attention for sensing, actuation, structural health monitoring and energy harvesting applications in the past two decades due to their excellent coupling between energy in the mechanical and electrical domains. Among all piezoceramic materials, lead zirconate titanate (PZT) has been the most broadly studied and implemented, in industrial applications due to its high piezoelectric coupling coefficients. Piezoceramic materials are most often employed as thin films or monolithic wafers. While there are numerous methods for the synthesis of PZT films, the sol-gel processing technique is the most widely used due to its low densification temperature, the ease at which the film can be applied without costly physical deposition equipment and the capability to fabricate both thin and thick films. However, the piezoelectric properties of PZT sol-gel derived films are substantially lower than those of bulk materials, which limit the application of sol-gel films. In comparison, single crystal PZT materials have higher piezoelectric coupling coefficients than polycrystalline materials due to their uniform dipole alignment. This paper will introduce a novel technique to enhance the piezoelectric properties of PZT sol-gel derived ceramics through the use of single crystal PbZr0.52Ti0.48O3 microcubes as an inclusion in the PZT sol-gel. The PZT single crystal cubes are synthesized through a hydrothermal based method and their geometry and crystal structure is characterized through scanning electron microscopy (SEM) and X-ray diffraction (XRD). A mixture of PZT cubes and sol-gel will then be sintered to crystallize the sol-gel and obtain full density of the ceramic. XRD and SEM analysis of the cross section of the final ceramics will be performed and compared to show the crystal structure and microstructure of the samples. The P-E properties of the samples will be tested using a Sawyer-Tower circuit. Finally, a laser interferometer will be used to directly measure the piezoelectric strain-coupling coefficient of the PZT sol-gel ceramics with and without PZT cube inclusions. The results will show that with the integration of PZ0.52T0.48 crystal inclusions the d33 coupling coefficient will increase more than 200% compared to that of pure PbZr0.52Ti0.48O3 sol-gel.

Lin, Yirong; Andrews, Clark; Sodano, Henry A.

2010-04-01

398

Preparation and mechanical properties of silicon oxycarbide fibers from electrospinning/sol-gel process  

SciTech Connect

Graphical abstract: Ceramic fibers, silicon oxycarbide (SiOC) fibers were demonstrated and showed higher mechanical properties from electrospinning/sol-gel process at 1000 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer SiOC fibers with low cost are promising to substitute the non-oxide fibers. Black-Right-Pointing-Pointer Successful preparation of SiOC fibers by electrospinning/sol-gel process. Black-Right-Pointing-Pointer Confirmation of the designed product using material characterization methods. Black-Right-Pointing-Pointer The SiOC fibers prepared at 1000 Degree-Sign C possess higher strength (967 MPa). -- Abstract: Silicon oxycarbide (SiOC) fibers were produced through the electrospinning of the solution containing vinyltrimethoxysilane and tetraethoxysilane in the course of sol-gel reaction with pyrolysis to ceramic. The effect of the amount of spinning agent Polyvinylpyrrolidone (PVP) on the dope spinnability was investigated. At a mass ratio of PVP/alkoxides = 0.05, the spinning sol exhibited an optimal spinnable time of 50 min and generated a large quantity of fibers. Electrospun fibers were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM results revealed that the SiOC fibers had a smooth surface and dense cross-section, free of residue pores and cracks. The XPS results gave high content of SiC (13.99%) in SiOC fibers. The SiOC fibers prepared at 1000 Degree-Sign C had a high tensile strength of 967 MPa and Young's modulus of 58 GPa.

Wang, Xiaofei [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China)] [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China); Gong, Cairong, E-mail: gcr@tju.edu.cn [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China)] [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China); Fan, Guoliang [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China)] [School of Materials Sciences and Engineering, Tianjin University, 300072 Tianjin (China)

2011-12-15

399

Structural and optoelectronic characterization of TiO2 films prepared using the sol gel technique  

NASA Astrophysics Data System (ADS)

TiO2 is a versatile material that makes for fascinating study in any of its several physical forms: monocrystal, polycrystal, powder or thin film. Its enhanced photosensitivity to UV radiation and excellent chemical stability in acidic and aqueous media point to its excellent potential for use in a variety of applications, such as solar cells, electronic devices, chemical sensors and photocatalysts. Of late, thin films of TiO2 have permitted the study of physical and chemical properties that are almost impossible to examine in powders. Using the sol-gel technique, it was possible to prepare TiO2 films, and to specifically modify their characteristic properties by means of annealing treatments. Optical measurements carried out on sol-gel derived films produced results similar to those found in films prepared using the sputtering technique. The use of TiO2 films facilitates the study of the behaviour of crystalline structure, grain size, photoresponse, electrical conductivity in both darkness and light and energy band gap (Eg) as a function of treatment temperature. For the first time, it has been demonstrated that the photoconductivity of TiO2 becomes apparent at a treatment temperature of 350 °C, which means that below this temperature the material is not photosensitive. The photosensitivity (S) of TiO2 films prepared by the sol-gel technique reaches values between 100 and 104, surpassing by more than two orders of magnitude the photosensitivity of TiO2 in powder form. In addition, it was possible to study the surface crystalline structure, where TEM studies clearly revealed both the polycrystalline order and the atomic arrangements of the TiO2 films. Our findings will afford us an opportunity to better study the nature of TiO2 and to enhance its performance with respect to the above-mentioned applications.

Jiménez González, A. E.; Gelover Santiago, S.

2007-07-01

400

Preparation and characteristics of PLZT (8/65/35) thin films by sol-gel method  

NASA Astrophysics Data System (ADS)

(Pb,La)(Zr,Ti)O3 is a ferroelectric material which has excellent pyroelectric, dielectric and ferroelectric properties, and has a wide application prospect in the field of microelectronics and integrated circuit. A variety of techniques have been used for the deposition of ferroelectric thin films, among the processes, the sol-gel method has its advantages. In this study, the pyroelectric lead lanthanum zirconnate titanate (PLZT) (8/65/35) thin films were prepared on Pt (111)/Ti/SiO2/Si (100) substrates using sol-gel method and their characteristics were analyzed. The orientation and structural properties of the PLZT films were measured by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. It was found that PbTiO3 (PT) can promote the crystallinity of PLZT thin films. According to the results of the SEM, under the 700°C holding temperature, the lead content of PLZT films decreased with the increment of holding time. The ferroelectric hystersis loop, pyroelectric coefficient and dielectric constant were also measured. The electrical properties of the films were optimized by rapid thermal process (RTP) at 700°C. Ferroelectric hysteresis loop of PLZT thin film with PT seed layer was tested at the triangular wave voltage of 50V. The results showed that the remanent polarization (Pr) was 25.7 ?C/cm2 and the coercive strength (Ec) was 68 kV/cm. At 1 kHz, dielectric constant (?r) of 951 and dielectric loss (tan?) of 0.048 were obtained, respectively. The pyroelectric coefficient was 1125?C/m2K. The results demonstrated that PLZT thin films could be prepared by sol-gel method and had good ferroelectric, dielectric and pyroelectric properties.

Sun, Xiaotao; Liu, Weiguo; Zhou, Shun; Luo, Jianqiang

2011-08-01

401

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

PubMed

The evolution of structure in sol-gel derived mixed bridged silsesquioxane-niobium alkoxide sols and drying thin films was monitored in situ by small-angle X-ray scattering. Since sol-gel condensation of metal alkoxides proceeds much faster than that of silicon alkoxides, the incorporation of d-block metal dopants into silica typically leads to formation of densely packed nano-sized metal oxide clusters that we refer as metal oxide building blocks in a silica-based matrix. SAXS was used to study the process of niobia building block formation while drying the sol as a thin film at 40-80°C. The SAXS curves of mixed niobia-hybrid silica sols were dominated by the electron density contrast between sol particles and surrounding solvent. As the solvent evaporated and the sol particles approached each other, a correlation peak emerged. Since TEM microscopy revealed the absence of mesopores, the correlation peak was caused by a heterogeneous system of electron-rich regions and electron poor regions. The regions were assigned to small clusters that are rich in niobium and which are dispersed in a matrix that mainly consisted of hybrid silica. The correlation peak was associated with the typical distances between the electron dense clusters and corresponded with distances in real space of 1-3 nm. A relationship between the prehydrolysis time of the silica precursor and the size of the niobia building blocks was observed. When 1,2-bis(triethoxysilyl)ethane was first hydrolyzed for 30 min before adding niobium penta-ethoxide, the niobia building blocks reached a radius of 0.4 nm. Simultaneous hydrolysis of the two precursors resulted in somewhat larger average building block radii of 0.5-0.6 nm. This study shows that acid-catalyzed sol-gel polymerization of mixed hybrid silica niobium alkoxides can be rationalized and optimized by monitoring the structural evolution using time-resolved SAXS. PMID:23688717

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

2013-08-15

402

Structural and optical properties of YAG:Ce 3+ phosphors by sol-gel combustion method  

NASA Astrophysics Data System (ADS)

High-quality Ce 3+-doped Y 3Al 5O 12 (YAG:Ce 3+) phosphors were synthesized by a facile sol-gel combustion method. In this sol-gel combustion process, citric acid acts as a fuel for combustion, traps the constituent cations and reduces the diffusion length of the precursors. The XRD and FT-IR results show that YAG phase can form through sintering at 900 °C for 2 h. This temperature is much lower than that required to synthesize YAG phase via the solid-state reaction method. There were no intermediate phases such as YAlO 3 (YAP) and Y 4Al 2O 9 (YAM) observed in the sintering process. The average grain size of the phosphors sintered at 900-1100 °C is about 40 nm. With the increasing of sintering temperature, the emission intensity increases due to the improved crystalline and homogeneous distribution of Ce 3+ ions. A blue shift has been observed in the Ce 3+ emission spectrum of YAG:Ce 3+ phosphors with increasing sintering temperatures from 900 to 1200 °C. It can be explained that the decrease of lattice constant affects the crystal field around Ce 3+ ions. The emission intensity of 0.06Ce-doped YAG phosphors is much higher than that of the 0.04Ce and 0.02Ce ones. The red-shift at higher Ce 3+ concentrations may be Ce-Ce interactions or variations in the unit cell parameters between YAG:Ce 3+ and YAG. It can be concluded that the sol-gel combustion synthesis method provides a good distribution of Ce 3+ activators at the molecular level in YAG matrix.

Xia, Guodong; Zhou, Shengming; Zhang, Junji; Xu, Jun

2005-06-01

403

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: dissolution behaviour and biological properties after crystallisation.  

PubMed

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol-gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol-gels. After heating and powdering the sol-gels, dissolution behaviour was assessed using ion chromatography to measure Ca(2+) and PO4 (3-) ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue™ assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol-gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol-gel is fired. PMID:24052344

Tredwin, Christopher J; Young, Anne M; Abou Neel, Ensanya A; Georgiou, George; Knowles, Jonathan C

2014-01-01

404

Preparation of porous titania sol-gel matrix for immobilization of horseradish peroxidase by a vapor deposition method.  

PubMed

A new and facile vapor deposition method has been developed for the preparation of sol-gel matrix. This method was used to form a titania sol-gel thin film and to immobilize horseradish peroxidase (HRP) on a glassy carbon electrode surface for the production of an amperometric hydrogen peroxide biosensor. This process prevented the cracking of conventional sol-gel-derived glasses. The morphologies of both titania sol-gel and the enzyme membranes were characterized using scanning electron microscopy and proved to be chemically clean, porous, and homogeneous and to have a very narrow particle size distribution. The sol-gel-derived titania-modified electrode retained the enzyme bioactivity and provided for long-term stability of the enzyme in storage. In the presence of catechol as a mediator, the sensor exhibited a rapid electrocatalytic response (less than 5 s), a linear calibration range from 0.08 to 0.56 mM with a detection limit of 1.5 microM and a high sensitivity (61.5 microA mM(-1)) for monitoring of H2O2. Effects of pH and operating potential were also explored for optimum analytical performance by using the amperometric method. The apparent Michaelis-Menten constant of the encapsulated HRP was 1.89 +/- 0.21 mM. PMID:12139071

Yu, Jiuhong; Ju, Huangxian

2002-07-15

405

Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest.  

PubMed

The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach. PMID:24676487

Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T

2014-06-21

406

Preparation of chitosan-graft-(?-cyclodextrin) based sol-gel stationary phase for open-tubular capillary electrochromatography.  

PubMed

A novel open-tubular CEC column coated with chitosan-graft-(?-CD) (CDCS) was prepared using sol-gel technique. In the sol-gel approach, owing to the 3D network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. The column efficiencies of 55,000?163,000 plates/m for the isomeric xanthopterin and phenoxy acid herbicides using the sol-gel-derived CDCS columns were achieved. Good stabilities were demonstrated that the RSD values for the retention time of thiourea and isoxanthopterin were 1.3 and 1.4% (run to run, n = 5), 1.6 and 2.0% (day to day, n = 3), 2.9 and 3.1% (column to column, n = 3), respectively. The sol-gel-coated CDCS columns have shown improved separations of isomeric xanthopterin in comparison with CDCS-bonded capillary column. PMID:23595578

Lü, Haixia; Li, Qingyin; Yu, Xiaowei; Yi, Jiaojiao; Xie, Zenghong

2013-07-01

407

Synthesis and luminescence properties of encapsulated sol-gel glass samarium complexes  

NASA Astrophysics Data System (ADS)

Luminescence efficiency of lanthanide complexes generally largely depend on the choice of the organic ligand and the host matrix in which these complexes are doped. Two Sm(III) complexes, namely: Sm(III) dithicarbamate - Sm(L1)3B [L1 = (R)2NCS2B, R = C2H5 and B = 1,10-phenanthroline] and Sm(III) complex with the polytonic ligand L2 = N?, N?2-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide {Sm2-L2-(CH3COO)2; L2 = C16H16N6O2} are synthesized, these complexes are then trapped in sol-gel glass. Room temperature luminescence of Sm(L1)3B and {Sm2-L2-(CH3COO)2} complexes encapsulated in sol-gel glass are studied using a spectrofluorometer. Up on excitation by a UV light, ligand L1B absorbs this light and transfers it into the Sm(III) ions and emission bands were observed in the visible region and were attributed to f-f transitions of Sm(III). The observed emission indicated an efficient L1B ligand as a sensitizer, while ligand L2 shows no ability to work as a sensitizer. The branching ratio I4G5/2?6H9/2/I4G5/2?6H7/2) of electric dipole transition to magnetic dipole transition was used as an effective spectroscopic probe to predict symmetry of the site in which Sm(III) is located. The encapsulation of the Samaium complexes was performed for three reasons: (i) before rare earth (RE)-doped sol-gel glasses can be used in applications such as laser materials, several fluorescence quenching mechanisms must be overcome, we show in this work that lanthanide fluorescence is greatly enhanced by chelation and selecting a suitable host matrix (sol-gel) to accommodate the lanthanide complex, (ii) to improve the stability of the phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (iii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light.

Zaitoun, M. A.; Momani, K.; Jaradat, Q.; Qurashi, I. M.

2013-11-01

408

Sol–gel synthesis of vanadium pentoxide nanoparticles in air- and water-stable ionic liquids  

Microsoft Academic Search

Vanadium pentoxide (V2O5) nanoparticles were synthesized at moderate reaction temperatures by hydrolysis of VO[OCH(CH3)2]3 in two different air- and water-stable ionic liquids with the same anion: 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)amide\\u000a ([Py1,4]Tf2N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIM]Tf2N) via the sol–gel method using acetone and isopropanol either as refluxing solvents or as co-solvents. The cation type of\\u000a the ionic liquid affects the crystallinity, morphology,

Mohammad Al Zoubi; Hala K. Farag; Frank Endres

2009-01-01

409

Sol-gel fabrication of heteroepitaxial zirconia films on MgO(001) substrates  

Microsoft Academic Search

Zirconia films were fabricated by sol-gel dip coating of single-crystal MgO (001) substrates. Continuous polycrystalline layers of tetragonal zirconia, 40nm thick, were obtained after firing at 600oC. At higher temperatures, abnormal grain growth, substrate uncovering and film break-up into islands were observed. At 1300oC, single-crystal islands of tetragonal MgO-ZrO2 solid solution appeared to be heteroepitaxially grown on the MgO(001) substrate,

Rene Guinebretiere; Alain Dauger; Olivier Masson; Bernard Soulestin

1999-01-01

410

Polydimethylsiloxane\\/silica\\/titania composites prepared by solvent-free sol–gel technique  

Microsoft Academic Search

Composites based on polydimethylsiloxane incorporating silica and titania were prepared by mixing polydimethylsiloxane with\\u000a proper oxides precursors, tetraethyl-orthosilicate and tetrabutyl-orthotitanate. In the presence of environmental humidity\\u000a and in acid catalysis, hydrolysis\\/condensation processes take place with formation of oxides and concomitantly polymer crosslinking.\\u000a Partial replacement of SiO2 in a polydimethylsiloxane\\/silica composite with titania (both generated in situ by sol–gel process) affects

Mihaela Alexandru; Maria Cazacu; Alexandra Nistor; Valentina E. Musteata; Iuliana Stoica; Cristian Grigoras; Bogdan C. Simionescu

2010-01-01

411

Optical Spectroscopy of Hybrid Sol-Gel Coatings Doped with Noble Metals  

Microsoft Academic Search

Sol-gel coatings in the xM· (100-x) SiO2 system, (M = Cu, Ag and Au) x =0.1–10 mol%), are deposited on soda lime glass slides by using silicon tetramethoxide Si(OCH3)4) and methyltriethoxysilane (SiCH3[OCH2CH3]3) as silica precursors. Anhydrous CuCl, CuCl2 · 2H2O, Cu(NO3)2 · 3H2O, CuSO4 · 5H2O, AgNO3 and HAuCl4 · 3H2O are used as copper, silver and gold sources. Coatings

M. A. Villegas; M. A. García; J. Llopis; J. M. Fernández Navarro

1998-01-01

412

Surface and catalytic properties of acid metal carbons prepared by the sol gel method  

NASA Astrophysics Data System (ADS)

The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones.

Aguado-Serrano, J.; Rojas-Cervantes, M. L.; Martín-Aranda, R. M.; López-Peinado, A. J.; Gómez-Serrano, V.

2006-06-01

413

Dielectric function of sol-gel prepared nano-granular zinc oxide by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

ZnO thin films have been prepared by sol gel and deposited by spin coating. The dielectric function has been determined by spectroscopic ellipsometry. Ellipsometric spectra are inverted by a direct numerical method without using the standard fitting procedures. The obtained dielectric function presents a broad excitonic effect. The dielectric function is studied using Elliot excitonic theory including exciton plus band-to-band Coulomb interactions with standard Lorentzian broadening. A modification of this model dielectric function with independent bound and unbound exciton contributions is empirically proposed to improve modelling of the band gap excitonic peak.

Gilliot, Mickaël; Eypert, Céline; Hadjadj, Aomar

2013-11-01

414

Tailoring the Microstructure of Sol–Gel Derived Hydroxyapatite/Zirconia Nanocrystalline Composites  

PubMed Central

In this study, we tailor the microstructure of hydroxyapatite/zirconia nanocrystalline composites by optimizing processing parameters, namely, introducing an atmosphere of water vapor during sintering in order to control the thermal stability of hydroxyapatite, and a modified sol–gel process that yields to an excellent intergranular distribution of zirconia phase dispersed intergranularly within the hydroxyapatite matrix. In terms of mechanical behavior, SEM images of fissure deflection and the presence of monoclinic ZrO2 content on cracked surface indicate that both toughening mechanisms, stress-induced tetragonal to monoclinic phase transformation and deflection, are active for toughness enhancement. PMID:24764458

2011-01-01

415

Synthesis and characterization of sol-gel derived Cr2O3 nanoparticles  

NASA Astrophysics Data System (ADS)

Cr2O3 nanoparticles have been synthesized using sol-gel process in which Cr2O3 crystallizes at low temperature from an amorphous material prepared by adding Hydrazine Monohydrate ((NH2)2 H2O) to an aqueous solution of Chromium Nitrate (Cr(NO3)3 9H2O). The prepared nanoparticles have been characterized for their structure using X-ray Diffraction (XRD) and morphology using Scanning Electron microscopy (SEM). The particle size using Dynamic Light Scattering (DLS) was found to be 180 nm which is in accordance with the SEM data.

Balouria, Vishal; Singh, A.; Debnath, A. K.; Mahajan, Aman; Bedi, R. K.; Aswal, D. K.; Gupta, S. K.

2012-06-01

416

Synthesis of hybrid sol-gel coatings for corrosion protection of we54-ae magnesium alloy  

NASA Astrophysics Data System (ADS)

The present work shows some preliminary results related to the synthesis, characterization and corrosion evaluation of different hybrid sol-gel coatings applied on the WE54-AE magnesium alloy attending to the two experimental variables, i.e. the precursors ratio and the aging time, which may affect the quality and the electrochemical properties of the coatings resultant. The experimental results confirmed that, under some specific experimental conditions, it was possible to obtain homogeneous and uniform, porous coatings with good corrosion resistance that also permit to accommodate corrosion inhibitors.

Hernández-Barrios, C. A.; Duarte, N. Z.; Hernández, L. M.; Peña, D. Y.; Coy, A. E.; Viejo, F.

2013-11-01

417

Structural and electrical properties of sol-gel spin coated indium doped cadmium oxide thin films  

SciTech Connect

The indium doped CdO thin films have been prepared by the sol-gel spin coating technique and the influence of indium doping concentration on the structural and electrical properties of the deposited films has been investigated. The indium doping concentration in the solution has been varied from 0-10 wt% insteps of 2wt%. A indium doping concentration of 6wt% has been found to be optimum for preparing the films and at this stage a minimum resistivity of 5.92×10{sup ?4}? cm and a maximum carrier concentration of 1.20×10{sup 20}cm{sup ?3} have been realized.

Rajammal, R. [Department of Physics, M.V.M Govt. Arts College for Women, Dindigul-624001 (India); Savarimuthu, E., E-mail: savari56@gmail.com; Arumugam, S., E-mail: savari56@gmail.com [Department of Physcis, Gandhigram Rural Institute, Gandhigram-624302 (India)

2014-04-24

418

Terrace formation with a picoliter sol–gel droplet for spherical cavity Raman laser  

Microsoft Academic Search

We have successfully made terrace-microspheres for laser emission: micrometer-size spherical cavity laser having terrace-shaped\\u000a pumping-light entrance. Organic–inorganic hybrid materials in the binary system of 3-methacryloxypropyltrimethoxysilane (MOPS)\\u000a and tetramethoxysilane (TMOS) were used for preparing the terrace on glass microspheres by sol–gel technique. To make terrace\\u000a portion, a picoliter sol was supplied with a micro-capillary suppliers into the bottom of spheres and

Hiyori Uehara; Tetsuji Yano; Shuich Shibata

2011-01-01

419

Optical and electrical properties of multiferroic bismuth ferrite thin films fabricated by sol–gel technique  

Microsoft Academic Search

Single-phase multiferroic BiFeO3 thin films have been prepared on LaNiO3\\/Si(100) and Si(100) wafer via sol–gel technique. The films are polycrystalline with preferring orientation of (101). The film has a conspicuous absorption in the blue and green light region, and band gap of 2.74eV. The refractive index and the extinction coefficient of the film is about 2.36 and 0.06 at 600nm,

Dongji Huang; Hongmei Deng; Pingxiong Yang; Junhao Chu

2010-01-01

420

Sol-gel synthesis of barium titanate powders using barium acetate and titanium(IV) isopropoxide  

SciTech Connect

A sol-gel process for low-temperature preparation of BaTiO{sub 3} powders is described. Chemical polymerization between barium acetate and titanium(IV) isopropoxide leads to the formation of barium titanate gels. After suitable drying and calcination treatments, the barium titanate gels were converted to BaTiO{sub 3} powders. The barium titanate gels and powders were characterized by TGA, DTA, and XRD. The results of these analyses indicate that it is possible to obtain stoichiometric (Ba/Ti = 0.99), homogeneous, high-purity BaTiO{sub 3} powders using relatively inexpensive barium acetate as a starting material.

Phule, P.P.; Risbud, S.H. (Univ. of Arizona, Tucson (USA))

1988-03-01

421

Sol-gel synthesis of Pb-free thin-film nanomaterials for electrocaloric devices  

NASA Astrophysics Data System (ADS)

Lead-free BaxCa(1-x)TiO3, BaSnyTi(1-y)O3 and composite BaxCa(1-x)TiO3 / BaSnyTi(1-y)O3 thin films were synthesized by a sol-gel technique. A large electrocaloric effect is expected in the obtained films. Atomic force microscopy studies revealed that the thin films consists of ellipsoidal objects enclosed by an amorphous matrix. The electrical properties of synthesized nanomaterials were investigated by impedance spectroscopy.

Abrashova, E. V.; Kononova, I. E.; Moshnikov, V. A.; Nalimova, S. S.

2014-12-01

422

Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites  

DOEpatents

A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.

Guadalupe, Ana R. (San Juan, PR); Guo, Yizhu (San Juan, PR)

2001-05-15

423

Synthesis and photoluminescence properties of Al-O Ceramics obtained by a sol-gel method  

NASA Astrophysics Data System (ADS)

The Al-O phosphor powders were synthesized by the sol - gel method at the lower temperature of 773 K. From the results of the PL (photo luminescence) measurement, the emission intensities around 400 and 450 nm changed with heating temperatures. From the X-ray diffraction and the X-ray photoelectron spectroscopy measurements, the Al-O ceramics obtained has a similar structure of boehmite (AlOOH). The structural change caused mainly by the loss of the hydroxyl group related to the increase of emission intensities.

Arita, K.; Sawaguchi, N.; Inano, H.; Sasaki, M.

2011-10-01

424

Switching of lasing wavelength in a sol-gel laser with dynamic distributed feedback  

SciTech Connect

A scheme of switching the lasing wavelength of active centres in a sol-gel matrix excited by external laser radiation is proposed. A distributed feedback is formed during pumping by using a right-angle prism due to the interference of the direct and reflected pump beams. The lasing wavelength is determined by the period of the interference pattern, which depends on the convergence angle of interfering beams. Control is performed by a liquid-crystal cell, which changes the pump radiation polarisation, and a birefringent prism. As a result, the convergence angle of interfering beams changes, leading to a change in the interference pattern period and the excited radiation wavelength.

Balenko, V G; Trufanov, A N; Umanskii, B A; Dolotov, S M; Petukhov, V A

2011-09-30

425

Optoelectronic properties of sol-gel derived ZnO:Co: Effect of Co concentration  

NASA Astrophysics Data System (ADS)

This paper studies the sol-gel synthesis of ZnO:Co thin films as function of Co doping concentration. The derived films were evaluated by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction measurements, Raman spectroscopy and UV-Vis spectroscopy. SEM images show that the films are smooth with grains size ?50 nm. It was also found that Co incorporation can decreased the preferential growth in the (0 0 2) orientation and optical transparency. Electrical characterization reveals that the derived films are n-type that can be paired with a p-type material to form rectifying pn junctions.

Bu, Ian Yi-Yu

2014-11-01

426

Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate thin films  

NASA Astrophysics Data System (ADS)

Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate (PZT) films was studied by x-ray diffraction and transmission-electron microscopy (TEM). X-ray diffraction studies of PZT films on sapphire substrates indicated that the pyrochlore to perovskite phase transformation was completed at 650 °C. In contrast, TEM investigations of free-standing PZT films showed that the phase transformation was completed at much higher temperatures. This discrepancy in the behavior of free-standing films versus films on substrate can be related to the size effect.

Kwok, Chi Kong; Desu, Seshu B.

1992-03-01

427

Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.  

SciTech Connect

In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

2005-03-01

428

Electrochemical impedimetric sensor based on molecularly imprinted polymers/sol-gel chemistry for methidathion organophosphorous insecticide recognition.  

PubMed

We report here a novel method to detect methidathion organophosphorous insecticides. The sensing platform was architected by the combination of molecularly imprinted polymers and sol-gel technique on inexpensive, portable and disposable screen printed carbon electrodes. Electrochemical impedimetric detection technique was employed to perform the label free detection of the target analyte on the designed MIP/sol-gel integrated platform. The selection of the target specific monomer by electrochemical impedimetric methods was consistent with the results obtained by the computational modelling method. The prepared electrochemical MIP/sol-gel based sensor exhibited a high recognition capability toward methidathion, as well as a broad linear range and a low detection limit under the optimized conditions. Satisfactory results were also obtained for the methidathion determination in waste water samples. PMID:25159412

Bakas, Idriss; Hayat, Akhtar; Piletsky, Sergey; Piletska, Elena; Chehimi, Mohamed M; Noguer, Thierry; Rouillon, Régis

2014-12-01

429

An FT-IR study on Diels Alder reactions catalysed by heteropoly acid containing sol gel silica  

NASA Astrophysics Data System (ADS)

Following the general trend of using heterogeneous catalysts whenever possible, the replacement of traditional homogeneous Lewis acid catalysts for the Diels-Alder reaction is currently considered in the literature. In this contribution, we report the successful application of sol-gel derived tungstophosphoric acid-silica composites as catalysts in the reaction of 1,3-cyclohexadiene and 2-propenal. The reaction was monitored by in situ FT-IR spectroscopy following the changes in the fine structure of the ?(C?O) band. The catalytic activity of the sol-gel immobilised heteropoly acids seems to be comparable with that of more conventional sol-gel silica-aluminas and their selectivity is even better because Broensted acid sites are destroyed upon calcination of the dry gel.

Kukovecz, Á.; Kónya, Z.; Kiricsi, I.

2001-05-01

430

Luminescence of Eu(3+) doped SiO2 Thin Films and Glass Prepared by Sol-gel Technology  

NASA Technical Reports Server (NTRS)

Trivalent europium ions are an important luminophore for lighting and display. The emission of (5)D0 to (7)F2 transition exhibits a red color at about 610 nm, which is very attractive and fulfills the requirement for most red-emitting phosphors including lamp and cathode ray phosphorescence materials. Various EU(3+) doped phosphors have been developed, and luminescence properties have been extensively studied. On the other hand, sol-gel technology has been well developed by chemists. In recent years, applications of this technology to optical materials have drawn a great attention. Sol-gel technology provides a unique way to obtain homogeneous composition distribution and uniform doping, and the processing temperature can be very low. In this work, EU(3+) doped SiO2 thin films and glasses were prepared by sol-gel technology and their spectroscopic properties were investigated.

Castro, Lymari; Jia, Weiyi; Wang, Yanyun; Santiago, Miguel; Liu, Huimin

1998-01-01

431

Thio sol-gel process for the synthesis of titanium disulfide  

SciTech Connect

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 metal source is demonstrated. The alkoxide reacts at room temperature with H[sub 2]S to form a precipitate which is a precursor to the sulfide. Through infrared spectroscopy and chemical analysis of the powder and gas chromatographic analysis of the liquid byproducts of the reaction, it is shown that a partially sulfidized alkoxide precursor forms through the displacement of alkoxy groups from the alkoxide by sulfur-bearing thiol groups. This thiolysis reaction is very similar to that which occurs in the case of sol-gel reactions to form oxides. The alkoxy-thiol species then undergo condensation-polymerization by the liberation of H[sub 2]S. When it is heat-treated in H[sub 2]S, this precursor transforms to TiS[sub 2] at [approximately]700 C. Systematic heat treatments have been performed and the formation of TiS[sub 2] has been observed using X-ray diffractometry. The change in the morphology has also been studied using scanning electron microscopy.

Sriram, M.A.; Kumta, P.N. (Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering)

1994-05-01

432

“Beating speckles” via electrically-induced vibrations of Au nanorods embedded in sol-gel  

NASA Astrophysics Data System (ADS)

Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative ``speckle beats'' induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of ``beats'', for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged.

Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

2014-01-01

433

Application of fluorinated compounds to cotton fabrics via sol-gel  

NASA Astrophysics Data System (ADS)

The aim of this work was the study of the surface modification of cotton fibers to confer hydro and oil repellency to the fabrics. A surface treatment not involving the bulk of the fibers was chosen, so fabrics can maintain comfort properties. Moreover the study focused on an economical and environmental friendly process, in order to obtain an effective treatment with good fastness to washing. A modified silica based film was applied on fibers surface by sol-gel, comparing laboratory grade reagents with a commercial product as precursors and optimizing process parameters. From obtained results sol-gel can be indicated as a promising process to confer an effective and durable finishing to cotton fibers with low add-ons. Long impregnation times can significantly improve the treatment fastness, while ironing the washed samples can restore, at least partially, hydro and oil repellency lost after the washing. Obtained results were supported by a deep surface characterization of untreated, treated and washed samples. The best results were obtained using the commercial product as the only precursor. This is interesting for an industrial application, due to the low cost of this product if compared with the laboratory grade reagents investigated. Some applications of finished textiles can be for household use, technical garments, umbrellas or outdoor textiles.

Ferrero, Franco; Periolatto, Monica

2013-06-01

434

Versatile bio-ink for covalent immobilization of chimeric avidin on sol-gel substrates.  

PubMed

A bio-ink for covalent deposition of thermostable, high affinity biotin-binding chimeric avidin onto sol-gel substrates was developed. The bio-ink was prepared from heterobifunctional crosslinker 6-maleimidohexanoic acid N-hydroxysuccinimide which was first reacted either with 3-aminopropyltriethoxysilane or 3-aminopropyldimethylethoxysilane to form silane linkers 6-maleimide-N-(3-(triethoxysilyl)propyl)hexanamide or -(ethoxydimethylsilyl)propyl)-hexanamide. C-terminal cysteine genetically engineered to chimeric avidin was reacted with the maleimide group of silane linker in methanol/PBS solution to form a suspension, which was printed on sol-gel modified PMMA film. Different concentrations of chimeric avidin and ratios between silane linkers were tested to find the best properties for the bio-ink to enable gravure or inkjet printing. Bio-ink prepared from 3-aminopropyltriethoxysilane was found to provide the highest amount of active immobilized chimeric avidin. The developed bio-ink was shown to be valuable for automated fabrication of avidin-functionalized polymer films. PMID:21705202

Heikkinen, Jarkko J; Kivimäki, Liisa; Määttä, Juha A E; Mäkelä, Inka; Hakalahti, Leena; Takkinen, Kristiina; Kulomaa, Markku S; Hytönen, Vesa P; Hormi, Osmo E O

2011-10-15

435

Fluorescent properties of Tb-doped borosilicate glass films prepared by a sol-gel method  

NASA Astrophysics Data System (ADS)

Rare earth elements have been used as optical dopants in glasses for many years. Boro-silicate glass films doped with rare-earths were deposited on glass substrates by using a simple sol-gel method. To avoid the undesirable precipitation due to the different hydrolysis rates between silicon and boron alkoxides, two solutions were used for dip-coating separately. One solution consisted of silicon tetraethoxide, ethanol, water and terbium nitrate as the Tb dopant. Another consisted of triethyl borate. Layer-by-layer deposition was applied by dipping into solutions containing metal alkoxides in sequence. The fluorescence properties of Tb3+ were investigated for the boro-silicate samples in relation to the firing effect. As-deposited silicate and boro-silicate samples showed similar fluorescence spectra under UV excitation. After firings at about 800 degrees C, a remarkable increase of the Tb3+-ion fluorescence was observed for the boro-silicate samples, while the silicate sample showed a little increase in fluorescence intensity. These experimental results suggested the formation of boro- silicate network and the incorporation of Tb3+ into the boro-silicate matrix. The multilayer process was found useful to fabricate multi-component sol-gel films.

Tonooka, Kazuhiko; Shimokawa, Katsuyoshi; Nishimura, Okio

2001-04-01

436

A modified sol-gel technique for pore size control in porous aluminum oxide nanowire templates.  

PubMed

A modified sol-gel technique was developed to continuously vary the pore diameters in porous alumina templates for the purpose of growing nanowires. To coat the pore walls, the porous alumina film is initially soaked in a methanol/water solution to fill the pores with the desired concentration of water. The porous alumina film is then exposed to a solution of 3-aminopropyltriethoxysilane (APTES) in toluene, creating a surface layer of APTES. The concentration of water in the pores correlates with the thickness of the APTES polymer coating that is obtained. This approach exerts greater control over the extent of silane polymerization than traditional sol-gel reactions by limiting the amount of water present for reaction. Factors such as the APTES concentration, exposure time, and organic cosolvent choice did not influence the coating thickness. However, the density and thickness of the APTES coating can be manipulated by varying the pH of the methanol/water solution as well as post-treatment annealing. Further modification of the pore size was achieved by subsequent reaction of the APTES coating with poly(methyl methacrylate) (PMMA). The PMMA couples to amine groups on the APTES polymer surface by an aminolysis reaction. Bismuth telluride nanowires were electrodeposited in the polymer-coated porous alumina templates using previously established methods. Nanowire diameters were smaller when the nanowires were prepared in modified templates as anticipated. PMID:25425125

Kelly, Daniel N; Wakabayashi, Ryo H; Stacy, Angelica M

2014-11-26

437

TiO2/PCL hybrid materials synthesized via sol-gel technique for biomedical applications.  

PubMed

The aim of the present work has been the synthesis of organic/inorganic hybrid materials based on titanium dioxide and poly(?-caprolactone) (PCL) to be used in the biomedical field. Several materials have been synthesized using sol-gel methods by adding different amounts of polymer to the inorganic sol. The obtained gels have been characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The FT-IR data allowed us to hypothesize that the structure formed was that of an interpenetrating network, realized by hydrogen bonds between TiOH groups in the sol-gel intermediate species and carbonyl groups in the polymer repeating units. SEM and AFM analyses highlighted that the obtained materials were nanostructurated hybrids. To evaluate the biological properties of the hybrids, their bioactivity and cytotoxicity were investigated as a function of the PCL amount. The bioactivity of the synthesized systems was proven by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating human blood plasma (SBF). MTT cytotoxicity tests and Trypan Blue dye exclusion tests were carried out exposing NIH-3T3 mouse embryonic fibroblasts for 24 and 48h to extracts from the investigated hybrid materials. The results showed that all the hybrids had a non-cytotoxic effect on target cells. PMID:25492181

Catauro, M; Bollino, F; Papale, F; Marciano, S; Pacifico, S

2015-02-01

438

Combining Inkjet Printing and Sol-Gel Chemistry for Making pH-Sensitive Surfaces.  

PubMed

Today biomedical sciences are experiencing the importance of imaging biological parameters with luminescence methods. Studying 2D pH distribution with those methods allows building knowledge about complex cellular processes. Immobilizing pH sensitive nanoparticles inside hydrogel matrixes, in order to guarantee a proper SNR, could easily make stable and biocompatible 2D sensors. Inkjet printing is also well known as tool for printing images onto porous surfaces. Recently it has been used as a free-form fabrication method for building three-dimensional parts, and now is being explored as a way of printing electrical and optical devices. Inkjet printing was used either as a rapid prototyping method for custom biosensors. Sol-gel method is naturally bound with inkjet, because the picoliter-sized ink droplets evaporate quickly, thus allowing quick sol-gel transitions on the printed surface. In this work will be shown how to merge those technologies, in order to make a nanoparticles doped printable hydrogel, which could be used for making 2D/3D smart scaffolds able to monitor cell activities. An automated image analysis system was developed in order to quickly have the pH measurements from pH nanosensors fluorescence images. PMID:25547966

Orsi, Gianni; De Maria, Carmelo; Montemurro, Francesca; Chauhan, Veeren M; Aylott, Jonathan W; Vozzi, Giovanni

2015-01-01

439

New sol-gel materials for high energy applications in nonlinear optics  

NASA Astrophysics Data System (ADS)

Organic-inorganic hybrid materials, composed of inorganic oxide structures and interpenetrated cross-linked organic polymers, are promising candidates for electro/optical applications, combining the most important glasslike and polymerlike properties. This is particularly true when large laser power density is used: these materials show high laser damage resistance compared with that of polymeric systems. A deep study of effects and causes of laser damage has never been done, especially for hybrid materials. The mechanisms of optical damage depend on different factors like laser experimental parameters, such as pulse duration, beam size and wavelength, or the microstructural characteristics and defects of the material. Hybrid materials possessing desired shapes and optical and mechanical properties are well synthesized by the sol-gel technique. The use of Glycidoxypropyltrimethoxysilane (GPTMS) allows preparing heterogeneous and resistant materials, with good optical properties. Different sol-gel matrices have been prepared in order to study their laser damage resistance. The possibility of varying the catalysts and precursors or the synthesis protocol allows obtaining materials with similar chemical composition and different microscopical properties. By this way, it is possible to study the laser damage threshold of these samples and to find the way to enhance and optimize the laser damage resistance, useful in non-linear optical devices.

Fortunati, I.; Signorini, R.; Bozio, R.; Brusatin, G.; Guglielmi, M.

2007-09-01

440

Sol-gel replicated optics made from single point diamond turned masters exhibit fractal surface roughness  

SciTech Connect

Deterministic optics manufacturing, notably single point diamond turning (SPDT) has matured such that the current generation of machines is capable of producing refractive and reflective optics for the visible wavelength region that are quite acceptable for many applications. However, spiral tool marks are still produced that result in unwanted diffractive scattering from grating-like features having a spatial frequency determined by the machine feed, tool radius, and other influences such as vibration and material removal effects. Such regular artifacts are the characteristic of deterministic manufacturing methods such as SPDT. The authors present some initial findings suggesting that fractal, or non-deterministic surfaces can be produced by SPDT through sol-gel replication. The key is the large isotropic shrinkage that occurs through monolithic sol-gel replication (a factor of 2.5) that results in all features, including tooling marks, being reduced by that amount. The large shrinkage itself would be a laudable-enough feature of the replication process. However, by an as-yet-not understood manner, the replication process itself seems to alter the roughness character of the replicated surface such that it appears to be fractal when analyzed using contact profilometry and the power spectrum approach.

Bernacki, B.E.; Miller, A.C. Jr.; Evans, B.M. III [Oak Ridge National Lab., TN (United States); Moreshead, W.V.; Nogues, J.L.R. [GELTECH, Inc., Alachua, FL (United States)

1996-05-01

441

Biological evaluation of zirconia/PEG hybrid materials synthesized via sol-gel technique.  

PubMed

The objective of the following study has been the synthesis via sol-gel and the characterization of novel organic-inorganic hybrid materials to be used in biomedical field. The prepared materials consist of an inorganic zirconia matrix containing as organic component the polyethylene glycol (PEG), a water-soluble polymer used in medical and pharmaceutical fields. Various hybrids have been synthesized changing the molar ratio between the organic and inorganic parts. Fourier transform spectroscopy suggests that the structure of the interpenetrating network is realized by hydrogen bonds between the Zr-OH group in the sol-gel intermediate species and both the terminal alcoholic group and ethereal oxygen atoms in the repeating units of polymer The amorphous nature of the gels has been ascertained by X-ray diffraction analysis. The morphology observation has been carried out by using the Scanning Electron Microscope and has confirmed that the obtained materials are nanostructurated hybrids. The bioactivity of the synthesized system has been shown by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating the human blood plasma. The potential biocompatibility of hybrids has been assessed as performing indirect MTT cytotoxicity assay towards 3T3 cell line at 24, 48, and 72 h exposure times. PMID:24857491

Catauro, M; Papale, F; Bollino, F; Gallicchio, M; Pacifico, S

2014-07-01

442

Sol-Gel Derived Hydroxyapatite Coating on Mg-3Zn Alloy for Orthopedic Application  

NASA Astrophysics Data System (ADS)

In recent years, magnesium and its alloys have gained a lot of interest as orthopedic implant constituents because their biodegradability and mechanical properties are closer to that of human bone. However, one major concern with Mg in orthopedics is its high corrosion rate that results in the reduction of mechanical integrity before healing the bone tissue. The current study evaluates the sol-gel-derived hydroxyapatite (HA) coating on a selected Mg alloy (Mg-3Zn) for decreasing the corrosion rate and increasing the bioactivity of the Mg surface. The mechanical integrity of the coating is established as a function of the surface roughness of the substrate and the sintering temperature of the coating. Coating on a substrate roughness of 15-20 nm and sintering at 400°C shows the mechanical properties in similar range of bone, thus making it suitable to avoid the stress-shielding effect. The hydroxyapatite coating on the Mg alloy surface also increases corrosion resistance very significantly by 40 times. Bone cells are also found proliferating better in the HA-coated surface. All these benefits together establish the candidature of sol-gel HA-coated Mg-3Zn alloy in orthopedic application.

Singh, Sanjay; Manoj Kumar, R.; Kuntal, Kishor Kumar; Gupta, Pallavi; Das, Snehashish; Jayaganthan, R.; Roy, Partha; Lahiri, Debrupa

2015-03-01

443

NiO-silica based nanostructured materials obtained by microemulsion assisted sol-gel procedure  

SciTech Connect

Graphical abstract: TEM micrograph of NiO/SiO{sub 2} nanoparticles. Highlights: {yields} Microemulsion assisted sol-gel procedure for NiO silica nanomaterials synthesis. {yields} Controlling the size and shape of nanoparticles and avoiding their aggregation. {yields} Narrow band-gap semiconductors (energies <3 eV) absorbing VIS or near-UV light biologically and chemically inert semiconductors entrapping/coating in silica network. {yields} Low cost as the microemulsion is firstly used in water metallic cation extraction. -- Abstract: NiO-silica based materials have been synthesized by microemulsion assisted sol-gel procedure. The versatility of these soft nanotechnology techniques has been exploited in order to obtain different types of nanostructures, such as NiO nanoparticles, NiO silica coated nanoparticles and NiO embedded in silica matrix. These materials have been characterized by adequate structural and morphology techniques: DLS, HR-TEM/SAED, BET, AFM. Optical and semiconducting properties (band-gap values) of the synthesized materials have been quantified by means of VIS-NIR diffuse reflectance spectra, thus demonstrating their applicative potential in various electron transfer phenomena such as photocatalysis, electrochromic thin films, solid oxide fuel cells.

Mihaly, M.; Comanescu, A.F. [University POLITEHNICA Bucharest, Faculty of Applied Chemistry and Materials Science, 1 Polizu, 011061 Bucharest (Romania)] [University POLITEHNICA Bucharest, Faculty of Applied Chemistry and Materials Science, 1 Polizu, 011061 Bucharest (Romania); Rogozea, A.E. [ILIE MURGULESCU Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)] [ILIE MURGULESCU Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Vasile, E. [METAV Research and Development, 31 C.A. Rosetti, 020011 Bucharest (Romania)] [METAV Research and Development, 31 C.A. Rosetti, 020011 Bucharest (Romania); Meghea, A., E-mail: a.meghea@gmail.com [University POLITEHNICA Bucharest, Faculty of Applied Chemistry and Materials Science, 1 Polizu, 011061 Bucharest (Romania)

2011-10-15

444

A Guided Materials Screening Approach for Developing Quantitative Sol-gel Derived Protein Microarrays  

PubMed Central

Microarrays have found use in the development of high-throughput assays for new materials and discovery of small-molecule drug leads. Herein we describe a guided material screening approach to identify sol-gel based materials that are suitable for producing three-dimensional protein microarrays. The approach first identifies materials that can be printed as microarrays, narrows down the number of materials by identifying those that are compatible with a given enzyme assay, and then hones in on optimal materials based on retention of maximum enzyme activity. This approach is applied to develop microarrays suitable for two different enzyme assays, one using acetylcholinesterase and the other using a set of four key kinases involved in cancer. In each case, it was possible to produce microarrays that could be used for quantitative small-molecule screening assays and production of dose-dependent inhibitor response curves. Importantly, the ability to screen many materials produced information on the types of materials that best suited both microarray production and retention of enzyme activity. The materials data provide insight into basic material requirements necessary for tailoring optimal, high-density sol-gel derived microarrays. PMID:24022739

Helka, Blake-Joseph; Brennan, John D.

2013-01-01

445

Synthesis, characterization and sol-gel entrapment of a crown ether-styryl fluoroionophore.  

PubMed

The synthesis and initial evaluation of a new dye-functionalized crown-ether, 2-[2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxacyclooctadecin)ethenyl]-3-methyl benzothiazolium iodide (denoted BSD), are reported. This molecule contains a benzyl 18-crown-6 moiety as the ionophore and a benzothiazolium to spectrally transduce ion binding. Binding of K(+) to BSD in methanol causes shifts in the both absorbance and fluorescence emission maxima, as well as changes in the molar absorptivity and the emission intensity. Apparent dissociation constants (K(d)) in the range 30-65 microm were measured. In water and neutral buffer, K(d) values were approximately 1 mm. BSD was entrapped in sol-gel films composed of methyltriethoxysilane (MTES) and tetraethylorthosilicate (TEOS) with retention of its spectral properties and minimal leaching. K(+) binding to BSD in sol-gel films immersed in pH 7.4 buffer causes significant fluorescence quenching, with an apparent response time of approximately 2 min and an apparent K(d) of 1.5 mm. PMID:19253273

Sui, Zhijie; Hanan, Nathan J; Phimphivong, Sam; Wysocki, Ronald J; Saavedra, S Scott

2009-01-01

446

In situ electrodeposition of an asymmetric sol-gel membrane based on an octadecyltrimethoxysilane Langmuir film.  

PubMed

The unique properties of Langmuir film formation were utilized in assembling a thin skin of an asymmetric membrane. An octadecyltrimethoxysilane (ODTMS) Langmuir monolayer was formed at the air-water interface and served as the substrate for growing a bulky sol-gel polymer in situ. The latter was based on the electrochemical deposition of tetramethoxysilane dissolved in the water subphase by means of horizontal touch electrochemistry. The resultant asymmetric layer that consisted of a thin hydrophobic ODTMS Langmuir film connected to a bulk hydrophilic sol-gel network was studied in situ and ex situ by using various techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, transmission electron microscopy (TEM), and goniometry. We found that a porous hydrophilic film grew on top of a hydrophobic layer as was evident from TEM, contact angle, and EIS analyses. The film thickness and film permeability could be controlled by changing the deposition conditions such as the potential window applied and its duration. Hence, this method offers an alternative approach for assembling asymmetric films for various applications. PMID:25111107

Hitrik, Maria; Lev, Ovadia; Mandler, Daniel

2014-09-15

447

Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels.  

PubMed

The phospholipid fatty acid (PLFA) content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS). Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm) of the input microbial suspension (R2 = 0.99). After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0) to their metabolic precursors (16:1?7 + 18:1?7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications. PMID:25690547

Trögl, Josef; Jirková, Ivana; Kurá?, Pavel; Akhmetshina, Elmira; Brovdyová, Ta?jána; Sirotkin, Alexander; Kirilina, Tatiana

2015-01-01

448

“Beating speckles” via electrically-induced vibrations of Au nanorods embedded in sol-gel  

PubMed Central

Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative “speckle beats” induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of “beats”, for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged. PMID:24413086

Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

2014-01-01

449

Design of photoinduced relief optical devices with hybrid sol gel materials  

NASA Astrophysics Data System (ADS)

Photosensitive organic-inorganic compounds appear as an alternative option for the design of new optical devices since they combine the characteristics of both glasses and photopolymers and improve the properties of the final material. These hybrid materials consisted of methacryloxypropyltrimethoxysilane, titanium isopropoxide, methacrylic acid and a photoinitiator. The hybrid sol-gel film was obtained via hydrolysis-condensation reactions and coating on a substrate. Spatially controlled UV irradiation induced the polymerization of the organic parts 1, thus, leading to structural changes and relief generation. Due to the characteristics of the sensitive material, no further etching is required to reveal the surface corrugation. These new innovative advanced materials, open up new vistas in the field of optical devices. Hybrid glasses, in which the organic and inorganic phases are blended at the sub-micrometric scale, are transparent and with low optical loss. In addition, they are harder than organic polymers but less brittle than silica. Hybrid sol-gel glasses generated by this self-developing process are shown to be suitable for generation of optical components such as diffraction gratings.

Soppera, O.; Croutxé-Barghorn, C.; Carré, C.; Blanc, D.

2002-01-01

450

Hydrationbehavior of C 2 S and C 2 AS nanomaterials,synthetized by sol–gel method  

Microsoft Academic Search

Hydration\\u000a behavior of dicalcium silicate (C2S) (Cement chemistry\\u000a nomenclature is used where C=CaO, S=SiO2, A=Al2O3, \\u000a $$ \\\\overline S $$\\u000a S=SO3) and gehlenite (C2AS),\\u000a synthesized by sol–gel method was investigated by means of isothermal\\u000a heat flow calorimeter at different temperatures. These phases were obtained\\u000a by crystallization processing at different temperatures from their xerogels\\u000a (nano-crystalline) prepared by the sol–gel method at ambient

M. Dovál; M. Palou; S. C. Mojumdar

2006-01-01

451

Fiber-optic dissolved oxygen and dissolved carbon dioxide sensors using fluorophores encapsulated in sol gel matrices  

Microsoft Academic Search

Fiber optic chemical sensors (FOCS) for oxygen, dissolved oxygen (DO), and dissolved CO2 sensing using thin films of fluorophores encapsulated in sol-gel matrices were made and tested. The DO\\/O2 sensor used ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) perchlorate (Ru(Ph 2Phen)Cl2) as the oxygen sensitive fluorophore and methyltrimethoxysilane (MTMS) sol-gel as the encapsulating matrix material. For the DCO2 sensor, 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) co-doped

Hyeog-Chan Kwon

2002-01-01

452

Selective formation of isobutane and isobutene from synthesis gas over zirconia catalysts prepared by a modified sol-gel method  

SciTech Connect

Zirconium oxide was synthesized by a modified sol-gel method, and was evaluated for the selective formation of isobutane and isobutene from synthesis gas. Due to increased basicity, zirconia from sol-gel preparation showed higher selectivities to iso-C[sub 4]'s while maintaining the same level of activity as zirconia prepared by calcination of zirconyl salts. The catalysts was further modified with Group I and II elements, and the activity tests showed increased iso-C[sub 4] and decreased methane production for the catalysts doped with potassium, magnesium, calcium, or barium. 29 refs., 10 figs., 1 tab.

Feng, Z.; Postula, W.S.; Erkey, C.; Philip, C.V.; Akgerman, A.; Anthony, R.G. (Texas A M Univ., College Station, TX (United States))

1994-07-01

453

Development and characterization of a family of shape memory, biocompatible, degradable, porous (co)-polyurethanes via sol-gel chemistry  

NASA Astrophysics Data System (ADS)

In support of the goal of a tissue engineering scaffold that is moldable, biodegradable and has shape-memory, this work explored the space of polyurethane sol-gel formulations and solvents to create a biocompatible, porous xerogel with potential to be such a porous scaffold. The work has resulted in both a process and a sol-gel formulation to effectively create a family of degradable, biocompatible, shape memory, porous, block copolyurethane xerogels from polycaprolactone and castor oil. Formulations of the sol-gel family of potential scaffolds were characterized for their biocompatibility, hydrolytic degradability, porosity, and shape memory. Of the scaffolds tested in this fashion, the most successful supported the attachment and growth of 3T3 fibroblast cells at 72% of the rate of attachment and growth in the standard tissue culture plastic Petri dishes. A method was developed and explained that selects the solvent for creation of a porous xerogel by controlling the phase separation of the polymerizing polyurethane from the reaction solution. This method uses standard polymer solvent swelling and extraction test data. Solvent solutions plotted in the 3-D space of Hansen solubility parameters were used to