These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

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

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

4

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

5

A novel sol-gel route to pinhole-free iron sulfide thin films  

Microsoft Academic Search

The general purpose of the study is to fabricate and improve upon FeS2 thin films which can be used as the photon absorber layer for a heterojunction or homojunction solar cell. This work deals with the preparation of the pyrite by an unconventional sol-gel approach. Thin pyrite films were prepared by sulfurizing the iron oxide films previously deposited through the

S. Kment; H. Kmentova; A. Sarkar; R. J. Soukup; N. J. Ianno; J. Krysa; Z. Hubicka; J. Olejnicek; C. L. Exstrom; S. A. Darveau

2011-01-01

6

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

7

Hydroxyapatite and fluor-hydroxyapatite layered film on titanium processed by a sol-gel route for hard-tissue implants  

Microsoft Academic Search

A double-layered coating, consisting of a hydroxyapatite (HA) outer film and a fluor-hydroxyapatite (FHA) inner film, was produced on a Ti substrate by a sol- gel route to improve the biocompatibility and functionality of the system. Dissolution behavior of and in vitro cellular responses to the layered film were investigated. Calcium nitrate and triethyl phosphite were used for calcium and

Hae-Won Kim; Jonathan C. Knowles; Vehid Salih; Hyoun-Ee Kim

2004-01-01

8

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

9

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

NASA Astrophysics Data System (ADS)

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

Wei, Qiong; Chen, Donghua

2010-10-01

10

Preparation of high surface area titania (TiO 2) films and powders using particulate sol–gel route aided by polymeric fugitive agents  

Microsoft Academic Search

High specific surface area (SSA) nanocrystalline powders and dip-coated TiO2 films have been prepared by particulate sol–gel route aided with polymeric fugitive agents (PFA), namely trehalose dihydrate (THD), polyethylene glycol (PEG6000) and hydroxypropyl cellulose (HPC). Powders obtained without PFA, heat-treated at 160°C show a SSA of 181m2\\/g, a value that could be increased up to 271 and 223m2\\/g for samples

M. R. Mohammadi; M. C. Cordero-Cabrera; D. J. Fray; M. Ghorbani

2006-01-01

11

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

12

Sensor performance of nanostructured TiO 2 thin films derived from particulate sol–gel route and polymeric fugitive agents  

Microsoft Academic Search

High specific surface area (SSA) nanocrystalline powders and dip-coated TiO2 thin films have been prepared by a particulate sol–gel route with added polymeric fugitive agents (PFAs), namely trehalose dihydrate (THD), polyethylene glycol (PEG6000) and hydroxypropyl cellulose (HPC). One of the highest SSA reported in the literature, obtained without PFA, was achieved (i.e., 181m2\\/g), a value that could be increased up

M. R. Mohammadi; D. J. Fray; M. C. Cordero-Cabrera

2007-01-01

13

A convenient sol-gel route for the synthesis of salicylate-titania nanocomposites having visible absorption and blue luminescence  

SciTech Connect

Syntheses of titania-based nanomaterials by simple sol-gel route using a mixture of CTAB and salicylate as well as salicylate ions as templates have been reported. The materials are characterized by the powder X-ray diffraction (XRD), thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and spectroscopic (FT IR, UV-VIS) analyses. A disordered mesoscale orientation of nanoparticles (ca. 2-4 nm) composed of TiO{sub 2}-salicylate surface complex has been obtained when 1:1 mixing ratio of CTAB and salicylate at the CTAB concentration of 0.001 M was employed as a template. All these nanocomposites exhibit a considerable red shift at the onsets of their absorption band compared to pure (organic-free) nanocrystalline TiO{sub 2} and show blue luminescence at room temperature. This assembly of nanoparticles is highly interesting in the context of visible light sensitization and nanodevice fabrication. - Graphical abstract: A new titania-salicylate nanostructure material has been synthesized, which exhibit a considerable red shift towards the visible region vis-a-vis nanocrystalline (organic-free) TiO{sub 2} and blue luminescence at room temperature.

Mitra, Atanu [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Bhaumik, Asim, E-mail: msab@iacs.res.i [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Nandi, Mahasweta; Mondal, John [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Roy, B.K. [Haldia Government College, Purba Medinipur 721657, West Bengal (India)

2009-05-15

14

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

15

Luminescent properties and the morphology of SrMoO 4 :Eu 3+ powders synthesized via combining sol-gel and solid-state route  

Microsoft Academic Search

SrMoO4:Eu3+ red phosphors were prepared by combining sol-gel and solid-state route. Citric acid and ethylenediaminetetraacetic acid (EDTA),\\u000a employed as the chelating agents, were added to the aqueous solutions of metal nitrates. X-ray diffraction (XRD) and photoluminescent\\u000a spectra techniques (PL) were used to characterize the resultant powders. The results indicated the obtained SrMoO4:Eu3+ phosphors were fine powders with a particle size

Qiong Wei; Donghua Chen

2010-01-01

16

Optical and dielectric properties of CaBi4Ti4O15 films prepared from sol gel route  

Microsoft Academic Search

Calcium Bismuth Titanate (CBT) is the potential material for the high temperature piezoelectric and ferroelectric applications, and exhibits excellent property for the non-volatile FeRAM for various commercial applications. In the present study CBT thin films were prepared from sol gel technique using acetate precursor method and films were annealed over a wide temperature range (500degC-800degC). The crystallographic orientations of films

A. Tanwar; K. Sreenivas; V. Gupta

2009-01-01

17

Diluted magnetic semiconductor properties in Zn 1?x Cu x O nanoparticles synthesized by sol gel route  

Microsoft Academic Search

Nanoparticles of ZnO:Cu Diluted Magnetic Semiconductor (DMS) are prepared using sol gel method. The structural, optical and\\u000a EPR properties of them are investigated. The XRD patterns of them show the formation of polycrystalline and hexagonal wurtzite\\u000a structure without any secondary phase formation. The average size of particles ranges from 14 to 19 nm. In the optical absorption\\u000a study of the samples,

R. Elilarassi; P. Sambasiva Rao; G. Chandrasekaran

2011-01-01

18

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

NASA Astrophysics Data System (ADS)

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

Srinivasan, Radhakrishnan; Bolloju, Satish

2014-01-01

19

Optical properties of undoped and Mg doped CuCrO{sub 2} powders synthesized by sol-gel route  

SciTech Connect

In this work, CuCrO{sub 2} was synthesized by sol-gel method using citric acid as a gelling agent. The different parameters like ratio of citric acid to metal ions, calcination temperature, and duration were studied. A green colored powder with particle size around 300 nm was formed at the calcination temperature of 800 °C for four hours duration. The increase in temperature has a profound impact on crystallite size and in turn effected the optical properties. Band gap of the obtained CuCrO{sub 2} has varied from 2.3 to 1.7 eV by increasing the temperature from 800 °C to 900 °C. Doping studies were performed by introducing Mg{sup 2+} ion to substitute Cr{sup 3+} in CuCrO{sub 2}. X-ray powder diffraction and SEM studies on 2% Mg doped samples indicated a clear formation of side phases. According to the X-ray powder patterns, the reflections from side phases were increasing with the increase in doping concentrations of Mg from 2 to 5%. The side phases were found to be MgCr{sub 2}O{sub 4} spinel and CuO. The band gap has decreased for doped samples in comparison to undoped one. In this paper, sol-gel synthesis and characterization by Xray powder diffraction, SEM studies and UV-Vis-Diffuse Reflectance spectra are presented.

Srinivasan, Radhakrishnan; Bolloju, Satish [Department of Chemistry, BITS Pilani Hyderabad Campus, Jawahar Nagar Village, Shamirpet Mandal, R.R.District, Hyderabad - 500 078 (India)

2014-01-28

20

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

21

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

22

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

NASA Astrophysics Data System (ADS)

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

Haitao, Liu; xiaohui, Wang; Longtu, Li

2009-09-01

23

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

24

Luminescence studies on solid and nanostructured SiO2:Eu3+ spheres obtained by sol-gel route  

NASA Astrophysics Data System (ADS)

Rare earths in confined systems are studied because their possible imaging applications. In this work we studied the optical properties of Eu3+ inside nanoporous spheres. Their properties were compared with these from europium in solid SiO2 spheres prepared by sol-gel method. Nanoporus channels were produced by using a surfactant. The last one was removed by chemical procedure. Then, europium was incorporated into the channels. XRD reveals the hexagonal structure of the pores. That was confirmed by HRTEM that shows the channels, clearly. N2 adsorption- desorption isotherm Type IV, characteristic of mesoporous materials, was obtained by BET. The I(5D0?7F2)/I(5D0?7F1) asymmetry ratio from Eu3+ transitions was obtained by photoluminescence. It had a value of 2.65 in the solid spheres and 1.65 in the nanoporous ones. That means Eu3+ is in an asymmetric site in both systems, and asymmetry is bigger in the solid spheres. Because the differences, we can use this parameter to distinguish between both systems, easily. Photoluminescence lifetimes were obtained for the 5D0 ? 7F2 emission. It was shorter in the solid spheres than in the nanoporous ones, confirming there is a more asymmetric site for the rare earth in the first case. IR spectra shows Eu3+ is not incorporated as part of the SiO2 network.

García-Macedo, J. A.; Terán H., E.; Franco, A.

2014-09-01

25

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

26

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

27

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

PubMed

In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350°C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65nm was obtained at 800°C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5h with pseudo first order rate constants of 5.85×10(-3) and 8.38×10(-3)min(-1), respectively. PMID:24835935

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

2014-10-15

28

Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants.  

PubMed

Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TIO2) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850 degrees C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850 degrees C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented. PMID:15348164

Piveteau, L D; Girona, M I; Schlapbach, L; Barboux, P; Boilot, J P; Gasser, B

1999-03-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

30

Nanocrystal/sol-gel nanocomposites  

SciTech Connect

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

31

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

32

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

33

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

34

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

NASA Astrophysics Data System (ADS)

Magnetic particles of W-type barium-calcium hexaferrite (BaCa2Fe16O27) have been synthesized using a Stearic acid gel route. The gel precursors were dried at 100° C for 2 hrs and then calcinated at 650° C, 750° C, 850° C and 950° C for 4 hrs in a furnace and slowly cooled to room temperature in order to obtain barium-calcium hexaferrite particles. The microscopic magnetic properties of prepared samples studying using Mössbauer spectroscopy. Mössbauer spectra of all samples were recorded at room temperature. Mossbauer parameters like Isomer shift, Quadruple splitting etc. were calculated with respect to iron foil. Barium calcium hexaferrite samples heated at 650° C, 750° C, 850° C show relaxation type Mössbauer spectra along with paramagnetic doublet. The intensity of paramagnetic doublet increases with temperature confirm the presence of ferrous ions in the samples, where as sample calcinated at 950° C confirm the presence of ferrimagnetic phase with partial super paramagnetic nature of prepared hexaferrite sample.

Jotania, Rajshree; Chauhan, Chetna; Sharma, Pooja

2010-12-01

35

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

36

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

37

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

38

Sol-gel chemistry by ring-opening polymerization  

SciTech Connect

Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. The authors have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits them to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solvent is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which they have successfully demonstrated.

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-02-07

39

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

40

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

41

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

42

Sol-gel kinetics by NMR  

SciTech Connect

The chemical synthesis of advanced ceramic and glass materials by the sol-gel process has become an area of increasing activity in the field of material science. The sol-gel process provides a means to prepare homogeneous, high purity materials with tailored chemical and physical properties. This paper surveyed the nuclear magnetic resonance (NMR) studies of silicon-based sol-gel kinetics. A review of the various models which have been used to analyze the chemical kinetics of various sol-gel systems was presented. The utility of NMR spectroscopy was demonstrated in investigating the influence that various reaction conditions have on the reaction pathways by which sol-gel derived materials are synthesized. By observing in a direct fashion the chemical pathway of the sol-gel, it is often possible to relate the final properties of the material to the formulation and reaction conditions of the sol-gel. The study of reaction kinetics by NMR is expected to play an increasingly important role in understanding sol-gel processing and material properties. 15 refs. (DP)

Assink, R.A.; Kay, B.D.

1991-01-01

43

Encapsulation of enzymes and cells in sol-gel matrices for biosensor applications  

NASA Astrophysics Data System (ADS)

Porous silicate materials made by low temperature sol-gel process are promising host matrices for encapsulation of biomolecules. Their mechanical strength, chemical inertness, hydrophilic nature, and above all, their optical transparency makes them an exciting platform for development of biosensors. To date, researchers have focused on sol-gel routes using alkoxides for encapsulation of biomolecules. However, formation of alcohol as a byproduct is an undesired complication as it can have detrimental effect on the activity of entrapped biomolecules. We have developed a novel sol-gel process to encapsulate biological molecules (such as enzymes, antibodies and cells) that uses neutral pH, room temperature, and does not generate alcohol as a byproduct. The process uses sodium silicate as precursor and is carried out in two steps--preparation of a low pH silicate sol followed by gelation at neutral pH in a buffer containing biomolecules. We developed a novel homogeneous immunoassay for 2,4,6-trinitrotoluene (TNT), and have encapsulated the immunoassay reagents in sol-gel matrices to product dispersible biosensors for the detection of TNT. Using the sol-gel doped with immunoassay reagents, we can detect TNT at low ppm levels. We also report encapsulation of E. Coli cells expressing the enzyme organophosphorus hydrolase on the cell surface in sol-gel matrices. The cell- doped sol-gel material can be used to develop biosensors for detection of organophosphates.

Singh, Anup K.; Gupta, Alok; Mulchandani, Ashok; Chen, Wilfred; Bhatia, Rimple B.; Schoeniger, Joseph S.; Ashley, Carol S.; Brinker, C. J.

1999-12-01

44

Gas transport mechanisms through sol–gel derived templated membranes  

Microsoft Academic Search

Sol–gel polymerisation routes have been devised to produce microporous silica membranes for CO2\\/N2 gas separation. The micropores are produced by the thermo-destruction of organic ligands (so-called templates) covalently attached to the silica network. The thermal stability and structural evolution with temperature of these materials has been characterised with TGA, differential thermal analysis (DTA), FTIR, 13C CP MAS NMR and 29Si

G. D. West; G. G. Diamond; D. Holland; M. E. Smith; M. H. Lewis

2002-01-01

45

A combined sol-gel and spark plasma sintering route to produce highly dense and fine-grained La0.65Ca0.20Na0.15MnO3 ceramics for magnetocaloric applications  

NASA Astrophysics Data System (ADS)

Sol-gel chemistry and spark plasma sintering were coupled to produce fine-grained and dense La0.65Ca0.20Na0.15MnO3 ceramics and their magnetic properties were explored in order to evaluate their efficiency for domestic magnetocaloric applications. The obtained manganites crystallize in the rhombohedral symmetry (R-3c). They present grain size in the sub-micrometer range. Their density and their average grain size increase when the sintering temperature increases from 600 to 800 °C. This entails an increase of the Curie temperature (T C) and of the maximum of the magnetic entropy change, even if these values remain smaller than those measured on their bulk counterparts prepared by a conventional solid state route. However, the magnetic transition occurs on a broad temperature range, resulting in a relative cooling power reaching about 265 J Kg-1 for an applied magnetic field of 5 T. This value is very close to that previously measured on bulk La0.65Ca0.20Na0.15MnO3 ceramics and represents about 64% of that measured on the standard Gd. The ceramics produced here by a low-energy and time-consuming method can thus be considered as technically and economically valuable for the desired applications.

Abdallah-Ben Ammar, Amal; Ayadi, Firas; Nowak, Sophie; Lecoq, Hélène; Cheikrouhou-Koubaa, Wissem; Cheikhrouhou, Abdelwaheb; Ammar, Souad; Sicard, Lorette

2014-03-01

46

Biological response of human mesenchymal stromal cells to titanium grade 4 implants coated with PCL/ZrO2 hybrid materials synthesized by sol-gel route: in vitro evaluation.  

PubMed

The surface modification of implantable materials in order to improve their biological proprieties, including tissue tolerance and osseointegration ability, by means of functional coating deposition is a promising strategy to provide a firm fixation of the implants. In this study, organic/inorganic hybrid materials consisting of an inorganic zirconia-based matrix, in which a biocompatible polymer, poly(?-caprolactone) (PCL), has been incorporated at different percentages, have been synthesized via sol-gel route. Developed materials have been used to coat titanium grade 4 substrates by means of dip coating technique. Scanning electron microscopy (SEM) analysis of the obtained coatings has shown that films crack-free can be obtained for high levels of PCL. Chemical composition and interactions between organic and inorganic moieties have been studied by Attenuated Total Reflectance Fourier Transform InfraRed spectroscopy. The bone-bonding capability of the nanocomposite films has been evaluated in vitro by examining the appearance of an apatite layer on their surface when soaked in a simulated body fluid by means of SEM equipped with EDS microanalysis. In vitro biocompatibility assessment was performed in combination with human mesenchymal stromal cells (hMSCs). Materials were found to be non-toxic and supporting cell proliferation. Additionally, the coating material was not hampering the differentiation of hMSCs in an osteogenic medium. PMID:25491844

Catauro, M; Bollino, F; Papale, F; Mozetic, P; Rainer, A; Trombetta, M

2014-12-01

47

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

48

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

49

Sol-Gel Manufactured Energetic Materials  

Microsoft Academic Search

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

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

2005-01-01

50

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

51

Preparation and Optical Properties of Nanocomposites Containing Palladium Within Mesoporous Silica via Sol-Gel Chemistry  

Microsoft Academic Search

The preparation and optical characterization of nanocomposites comprised of palladium into mesoporous silica are presented in this paper. Introduction of palladium was conducted through two different routes involving the sol-gel technique. In the first route, monolithic porous silica produced by hydrolysis of alkoxides in advance was then impregnated into the concentrated solution containing palladium precursor, and the nanocomposite was manufactured

W. Yucheng; Z. Lide; L. Guanghai; Z. Yong; S. Guangmin

2002-01-01

52

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

53

Sol-gel lithium aluminate ceramics and tritium extraction mechanisms  

NASA Astrophysics Data System (ADS)

Systems based on the ?-lithium aluminate structure have potential applications as breeder materials for fusion reactors. LiAlO 2 ceramics with controlled stoichiometry and microstructure have been prepared by an alkoxide-hydroxide sol-gel route. These ceramics have been tested in out-of-reactor experiments. We have proposed an original model, taking into account diffusion and desorption mechanisms in series, to interpret the tritium extraction curves recorded on materials with different porosities. We show that, for identical chemical composition, the microstructure plays a central role for both limiting ionic diffusion and surface molecular desorption processes.

Renoult, O.; Boilot, J.-P.; Korb, J.-P.; Petit, D.; Boncoeur, M.

1995-03-01

54

Sol-gel based biofuel cell architectures  

NASA Astrophysics Data System (ADS)

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

Lim, James Robert

55

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

56

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

57

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

58

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

59

Sol-Gel Alumina Nano Composites for Functional Applications.  

E-print Network

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

Jayasankar, M

2009-01-01

60

The Sol-Gel Process for Nano-Technologies: New Nanocomposites with Interesting Optical and Mechanical Properties  

Microsoft Academic Search

Various nanocomposite systems have been synthesized by sol-gel routes. For this reason, prefabricated nanoparticles (SiO2 sols or boehmite powder) have been dispersed after surface modification in sol-gel-derived organically modified or polymeric ligand matrices. In all cases, a significant effect on dispersibility by surface modification could be observed. After curing, the mechanical or optical properties depend strongly on the dispersion and

H. K. Schmidt; E. Geiter; M. Mennig; H. Krug; C. Becker; R.-P. Winkler

1998-01-01

61

Characterization of sol-gel entrapped chlorophyllase.  

PubMed

Immobilization of membrane proteins remains a challenge compared to soluble proteins. The membrane protein-chlorophyllase was successful entrapped in tetramethoxysilane (TMOS)-based sol-gel in the presence of lipid. Activity was examined against mixing rate, incubation temperature, time, substrate, acetone, and canola oil concentration. The external mass transfer of chlorophyll is not the rate-limiting step at higher mixing rates. Stability against temperature and acetone as denaturant was enhanced. In spite of the fact that an initial reaction lag phase was observed, 20% more chlorophyll was hydrolyzed, compared to reaction with free enzyme by the end of a 12 h assay. The initial lower activity demonstrated by entrapped chlorophyllase is likely due to the diffusion resistance of chlorophyll into and within the entrapment matrix. This hypothesis was substantiated by a low diffusion coefficient on the order of 10(-14) m(2)/s obtained for chlorophyll in nanoporous sol-gel particles. Pore size distribution of nanoporous wet TMOS-based sol-gel with or without protein was determined by thermoporometry. The change in pore morphology upon doping with chlorophyllase suggests that protein acts as a template during the sol-gel process. PMID:16804946

Yi, Yunyu; Kermasha, Selim; Neufeld, Ronald

2006-12-01

62

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

63

Sol-Gel Derived Hafnia Coatings  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

64

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

65

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

66

Sol-gel based optical chemical sensors  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

67

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

68

Sol gels. (Latest citations from Materials Business file). Published Search  

SciTech Connect

The bibliography contains citations concerning sol gel derived materials. The citations examine research conducted by universities, corporations and government agencies for the development of novel sol gel processes, and commercial applications of these techniques. Uses of sol gels in the production of glass, ceramics, composites, protective coatings, and hybrid organic/inorganic materials are described. Other topics include new products, expanding markets for sol gel derived materials, and profit potential. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1996-01-01

69

Fabrication of Cu2ZnSn(S,Se)4 solar cells via an ethanol-based sol-gel route using SnS2 as Sn source.  

PubMed

Cu2ZnSn(S,Se)4 semiconductor is a promising absorber layer material in thin film solar cells due to its own virtues. In this work, high quality Cu2ZnSn(S,Se)4 thin films have been successfully fabricated by an ethanol-based sol-gel approach. Different from those conventional sol-gel approaches, SnS2 was used as the tin source to replace the most commonly used SnCl2 in order to avoid the possible chlorine contamination. In addition, sodium was found to improve the short-circuit current and fill factor rather than the open-circuit voltage due to the decrease of the thickness of small-grained layer. The selenized Cu2ZnSn(S,Se)4 thin films showed large densely packed grains and smooth surface morphology, and a power conversion efficiency of 6.52% has been realized for Cu2ZnSn(S,Se)4 thin film solar cell without antireflective coating. PMID:25000474

Zhao, Wangen; Wang, Gang; Tian, Qingwen; Yang, Yanchun; Huang, Lijian; Pan, Daocheng

2014-08-13

70

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

71

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

72

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

73

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

Microsoft Academic Search

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

Ganesh Suyal

2003-01-01

74

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

Microsoft Academic Search

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

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

2010-01-01

75

Sol–gel coatings of low sintering temperature for corrosion protection of ZE41 magnesium alloy  

Microsoft Academic Search

Silica coatings have been obtained through the organic sol–gel route on magnesium–zinc alloys (ZE41) using low sintering temperatures for their corrosion protection. Tetraethoxysilane (TEOS) was used as alkoxide precursor, and the coatings, monolayer and 3-layers, were deposited by dip-coating technique at a controlled extraction speed of 35cm\\/min. Temperatures of 135°C were applied for several hours for coating densification avoiding mechanical

A. J. López; J. Rams; A. Ureña

2011-01-01

76

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

Microsoft Academic Search

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

A. J. López; E. Otero; J. Rams

2010-01-01

77

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

78

Sol–gel derived YPO 4 and LuPO 4 phosphors, a spectroscopic study  

Microsoft Academic Search

LnPO4 (Ln=Y, Lu) orthophosphates have been prepared by a new sol–gel route. Eu3+ doped materials have also been synthesized and studied. X-ray diffraction performed on all samples showed that pure xenotime phase is obtained in all cases even for doped samples. The morphology of the powders has been determined and small grains with narrow size distribution are evidenced. Finally the

J. M. Nedelec; C. Mansuy; R. Mahiou

2003-01-01

79

Lead oxide coatings on sol-gel derived lead lanthanum zirconium titanate thin layers for enhanced crystallization into the perovskite structure  

Microsoft Academic Search

An improved method is described for the sol-gel preparation of PLZT thin layers in the perovskite structure. The method uses a PbO cover coat. Details are reported for the sol-gel processing route and heat-treatment conditions. Through use of this method it is possible to prepare single-phase perovskite material with improved properties. The deleterious effect of additional phases--which are not present

Toshihiko Tani; David A. Payne

1994-01-01

80

Formation and stabilization of tetragonal phase in sol–gel derived ZrO 2 treated with base-hot-water  

Microsoft Academic Search

Zirconia (ZrO2) nanoparticles have been prepared by sol–gel route. Low temperature crystallization using base-hot-water treatment (BHWT) was conducted for the sol–gel derived ZrO2 gel powders at 90°C and at pH 14 for various periods of time. Single phase nanocrystalline tetragonal ZrO2 (t-ZrO2) was successfully obtained by immersing the dry gel powders into hot, basic condition water and kept at rest

Niki Prastomo; Hiroyuki Muto; Mototsugu Sakai; Atsunori Matsuda

2010-01-01

81

Current issues in sol-gel reaction kinetics  

SciTech Connect

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

Assink, R.A.; Kay, B.D.

1990-01-01

82

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

83

Preparation and characterization of PZT solid solutions via sol gel process  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

84

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

85

Structural and dielectric/ferroelectric properties of (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} synthesized by sol-gel route  

SciTech Connect

A series of compounds with the general formula (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} (0.0{<=}x{<=}1.0) has been prepared by the sol-gel method. The decomposition of the gel was characterized by thermo-gravimetric analysis coupled to mass spectrometry, indicating the reaction is achieved above 850 {sup o}C. The lattice parameters versus x show an expected decrease in the a and b parameters while c and the {beta} angle remain almost unchanged with respect to the monoclinic symmetry conserved for the full solid solution. Dielectric, piezoelectric and ferroelectric properties were measured on the entire series. - Graphical abstract: XRD patterns of (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} powders for various x values. The (hkl) peaks positions (with h and k{ne}0) change with x values while the (00l) peaks positions remain unaffected.

Shao Zhenmian [Univ Lille Nord de France, F-59000 Lille (France); UArtois, UCCS, F-62300 Lens (France); CNRS, UMR 8181, F-59650 Villeneuve d'Ascq (France); ENSCL, UCCS, F-59652 Villeneuve d'Ascq (France); Saitzek, Sebastien, E-mail: sebastien.saitzek@univ-artois.f [Univ Lille Nord de France, F-59000 Lille (France); UArtois, UCCS, F-62300 Lens (France); CNRS, UMR 8181, F-59650 Villeneuve d'Ascq (France); Roussel, Pascal; Mentre, Olivier [Univ Lille Nord de France, F-59000 Lille (France); CNRS, UMR 8181, F-59650 Villeneuve d'Ascq (France); ENSCL, UCCS, F-59652 Villeneuve d'Ascq (France); Prihor Gheorghiu, Felicia; Mitoseriu, Liliana [University Al. I. Cuza Iasi, Department of Physics, Bv. Carol I, 11, Iasi 700506 (Romania); Desfeux, Rachel [Univ Lille Nord de France, F-59000 Lille (France); UArtois, UCCS, F-62300 Lens (France); CNRS, UMR 8181, F-59650 Villeneuve d'Ascq (France)

2010-07-15

86

Production of continuous mullite fiber via sol-gel processing  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

87

Li batteries with porous sol-gel cathodes  

Microsoft Academic Search

The structure presented is a high-capacity micro battery, lithium based, consisting of porous cathode, solid electrolyte and silver anode. A spinel LiNi0.4La0.1Mn1.5O4 sol–gel layer was deposited on a porous ceramic substrate to give high specific surface to the chip-like microbatteries. The anode used was thermally evaporated Ag and the electrolyte a sol–gel hybrid Li4SiO4 layer.

Antonela Dima; Francesco Della Corte; Maurizio Casalino; Ivo Rendina

2007-01-01

88

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

89

Dimer formation in phthalocyanine-doped sol-gel materials  

NASA Astrophysics Data System (ADS)

A number of different organic molecules have been used as optical probes of the sol-gel process. There is relatively little information, however, as to whether these molecules remain well isolated within the sol-gel structure or if they tend to form dimers or higher aggregates within the network. This issue is particularly important for doped sol-gel optical materials as dimer formation can exert a significant influence on the optical properties of dyes. The present paper uses the optical absorption characteristics of copper phthalocyanine tetrasulfonate (CuPcts) to determine how the state of the dye is affected by the chemical changes during the sol-gel process. The absorption spectra of CuPcts indicate that the dye molecules are dimerized in acid-catalyzed silica xerogels prepared from TMOS. The dimerization is largely controlled by the chemical environment inside the pores. By using appropriate reference solutions, we are able to identify the factors which cause dimerization and the stages of the sol-gel-xerogel transformation when the dimers form. These factors include the quantity of solvent remaining in the pores, the alcohol/water content of the solvent and its acidity. It is shown that by modifying the sol-gel processing conditions and the solvent chemistry within the pores, it is possible to reduce significantly dimer formation in silica xerogels.

Fuqua, Peter D.; Dunn, Bruce S.; Zink, Jeffrey I.

1994-10-01

90

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

91

Sol-gel derived contamination resistant antireflective coatings  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

92

Sol-gel derived contamination resistant antireflective coatings  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

93

Kinetics and structure of silicate sol-gels  

SciTech Connect

The structure of a silicate sol-gel derived material depends on the nature of its reaction kinetics. The chemical state of the silicate sol-gel is characterized by both the functional group concentrations and the distribution of the functional groups about a single silicon atom. {sup 29}Si nuclear magnetic resonance (NMR) spectroscopy provides a way to quantitatively determine these concentrations and distributions as a function of time during the reaction. During the early stages of the sol-gel reaction, the distribution of hydrolyzed species enables one to calculate the relative rates of hydrolysis. During the intermediate stages of the reaction, the rate of formation of various condensed species enables one to determine the reaction rate constants for both water-producing and alcohol-producing condensation. The chemical bonding of sol-gel derived solid materials can be determined by direct polarization NMR combined with magic angle spinning techniques. These capabilities provide a valuable tool for studying the relationships between the reaction conditions, the chemical kinetics and the resulting structure of the sol-gel derived material. 8 refs., 4 figs.

Assink, R.A.; Brinker, C.J.; Kay, B.D.

1990-01-01

94

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

95

Luminescence properties of Cr-doped silica sol gel glasses  

NASA Astrophysics Data System (ADS)

The emission of Cr-doped silica glass obtained by the sol- gel method is characterized by an orange broad band with a maximum at 610 nm. Its nature is examined by the absorption, excited state absorption, emission, excitation and lifetime measurements over a wide range of temperature and for different concentration of Cr ions. Our measurement show that in spite of fact that the absorption properties of Cr- doped silica sol-gel glass are predominantly associated with Cr4+ centers, the observed in visible range emission can be assigned neither to Cr3+ nor to Cr4+ ions. The discussion of the nature of observed emission was carried out for all possible valencies of the Cr ions. In conclusion is suggested that it may be ascribed to the transitions on the monovalent Cr1+ ion. The reducing agents occurring during the sol-gel process and leading to lowering the Cr valency are discussed.

Strek, Wieslaw; Lukowiak, Edward; Deren, Przemyslaw J.; Maruszewski, K.; Trabjerg, Ib; Koepke, Czeslaw; Malashkevich, G. E.; Gaishun, Vladimir E.

1997-11-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

97

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

98

Nanoporous titania–alumina mixed oxides—an alkoxide free sol–gel synthesis  

Microsoft Academic Search

A series of x TiO2 (1?x) Al2O3 mixed oxides with different molar ratio, x=0.95, 0.90, 0.80, 0.70 and 0.60 (where x=TiO2\\/TiO2+Al2O3), have been prepared by a non-alkoxide sol–gel route from a mixture of titania and boehmite sol derived from titanyl sulfate and aluminium nitrate. It was found that alumina introduces structural and textural modification to titania and the resultant properties

S Sivakumar; C. P Sibu; P Mukundan; P. Krishna Pillai; K. G. K Warrier

2004-01-01

99

Sol-gel derived YPO 4 and LuPO 4 phosphors, a spectroscopic study  

NASA Astrophysics Data System (ADS)

LnPO 4 (Ln=Y, Lu) orthophosphates have been prepared by a new sol-gel route. Eu 3+ doped materials have also been synthesized and studied. X-ray diffraction performed on all samples showed that pure xenotime phase is obtained in all cases even for doped samples. The morphology of the powders has been determined and small grains with narrow size distribution are evidenced. Finally the optical properties of the doped materials have been studied, the substitution of Eu 3+ for Ln 3+ is confirmed and the radiative lifetimes are compatible with potential applications of these phosphors.

Nedelec, J. M.; Mansuy, C.; Mahiou, R.

2003-06-01

100

Sensitive films based on porous sol-gel silica  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

101

Characterization of Hafnia Powder Prepared from an Oxychloride Sol Gel  

SciTech Connect

Hafnium containing compounds are of great importance to the semiconductor industry as a replacement for Si(O,N) with a high- gate dielectric. Whilst Hf is already being incorporated into working devices1, much is still to be understood about it. Here we investigate the crystallisation processes and chemistry of bulk HfO2 powders which will aid in interpretation of reactions and crystallisation events occurring in thin films used as gate dielectrics. Amorphous HfO2 powder was prepared via a sol-gel route using hafnium oxychloride (HfOCl2 xH2O) as a precursor. The powders were subjected to various heat treatments and analysed using x-ray diffraction (XRD) and thermal analysis techniques. It was found that a large change in the crystallisation pathway occurred when the sample was heated in an inert environment compared with in air. Instead of the expected monoclinic phase (m-HfO2), tetragonal HfO2 (t-HfO2) also formed under these conditions and was observed up to temperatures of ~760 C. The t-HfO2 particles, which are less than 30nm in size, eventually transform into m-HfO2 on further heating. Possible mechanisms for the crystallisation of t-HfO2 are discussed. It is proposed that within this temperature range t-HfO2 is stabilised due to the presence of oxygen vacancies in the inert environment, forming by the reduction of HfIV to HfIII. As the crystal grows in size as the temperature increases there are too few oxygen vacancies left in the structure to continue stabilising the t-HfO2 phase and so transformation to m-HfO2 occurs.

McGilvery, Catriona M. [Imperial College, London; De Gendt, S [Imperial College, London; Payzant, E Andrew [ORNL; MacKenzie, M [Imperial College, London; Craven, A J [Imperial College, London; McComb, D W [Imperial College, London

2011-01-01

102

Microstructural and antibacterial properties of zinc-substituted cobalt ferrite nanopowders synthesized by sol-gel methods  

NASA Astrophysics Data System (ADS)

Zinc-substituted cobalt ferrite nanopowders were prepared via a sol-gel route using citric acid as a chelating agent. The influence of zinc concentration on the microstructure, crystal structure, surface wettability, surface roughness, and antibacterial property of zinc-substituted cobalt ferrite nanopowders was investigated systematically. The substitution of zinc influences slightly the microstructure, surface wettability, surface roughness, and crystal structure but strongly affects the antibacterial property of the cobalt ferrite nanopowders.

Sanpo, Noppakun; Berndt, Christopher C.; Wang, James

2012-10-01

103

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

104

Inorganic Sensing Using Organofunctional Sol-Gel Materials  

PubMed Central

This Account describes recent work in the development and applications of sol-gel sensors for concentrated strong acids/bases and metal ions. The use of sol-gel films doped with organic indicators for the optical sensing of concentrated strong acids (HCl 1-10 M) and bases (NaOH 1-10 M) has been explored, and the development of dual optical sensor approaches for ternary systems (HCl-salt-H2O and NaOH-alcohol-H2O) to give acid and salt as well as base and alcohol concentrations is discussed. The preparation of transparent, ligand-grafted sol-gel monoliths is also described, and their use in the analysis of both metal cations (Cu2+) and anions [Cr(VI)] is presented. A new model using both metal ion diffusion and immobilization by the ligands in such monoliths has been developed to give metal concentrations using the optical monolith sensors. In addition to optical sensing, a method utilizing ligand-grafted sol-gel films for analyte preconcentration in the electrochemical determination of Cr(VI) has been explored and is discussed. PMID:17465520

Carrington, Nathan A.; Xue, Zi-Ling

2007-01-01

105

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...

106

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

107

OPTI 425(525)-Sol-Gel Science Course Description  

E-print Network

, separations science, chemical catalysis and coatings science. By definition the sol-gel process starts materials. The resulting films, precipitated powders, fibers or monolithic glasses are widely used, gelation and precipitation, effects of post- gelation processing and drying and structure property

Arizona, University of

108

Process of forming a sol-gel/metal hydride composite  

DOEpatents

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

Congdon, James W. (Aiken, SC)

2009-03-17

109

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

110

: comparison between magnetron sputtering and sol-gel synthesis  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

111

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

112

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

113

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

114

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

115

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

116

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

117

Radiation-induced densification of sol-gel SnO 2:Sb films  

NASA Astrophysics Data System (ADS)

Thin films of tin oxide doped with antimony (25 at.% nominal) were deposited on either silicon wafers or pyrex plates using the sol-gel dip coating technique. The samples processed on Si consist of a single layer of SnO 2:Sb dried at low temperature (150 °C) for 40 min. Three successive layers, subsequently dried and annealed at 500 °C for 1 h, were coated on pyrex substrates. Single and multilayered samples were then implanted at room temperature with Xe + ions in the 10 14-10 16 cm -2 fluence range. The incident energy (300 keV) was chosen so that the main part of collisional processes occured within the film. The atomic composition and density of the irradiated targets were determined using Rutherford backscattering spectrometry in conjunction with profilometry measurements. Structural informations were obtained from transmission electron microscopy performed on cross-sectional specimen. The results show that ion beam processing is a promising route to densify sol-gel SnO 2:Sb films without overheating the underlying substrate. As an example, the density of a single layer sample irradiated at the highest fluences exceeds 80% of bulk SnO 2 density, whereas only 45% of bulk density could be achieved by means of conventional annealing at 500 °C. A radiation-induced densification is also evidenced in the annealed multideposits. In this case, the whole film is polycrystalline before implantation and becomes amorphous in its densified part.

Canut, B.; Teodorescu, V.; Roger, J. A.; Blanchin, M. G.; Daoudi, K.; Sandu, C.

2002-05-01

118

Superhydrophobic sol-gel nanocomposite coatings with enhanced hardness  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

119

Sol gel-based fiber optic pH sensor  

NASA Astrophysics Data System (ADS)

We report here on the development of a sol-gel based fiber optic sensor to monitor local blood pH. These sensors are being developed for invasive medical applications; that is, they will be coaxially threaded through a catheter beyond an occlusion in the vascular system. The fiber optic pH sensor design was based on the immobilization of a pH sensitive dye, seminaphthorhodamine-1 carboxylate, onto the tip or surface of an optical fiber using the sol-gel method. The fiber optic pH sensor was tested in phosphate buffer saline and human whole blood using a miniature fluorimeter system. Linear responses were obtained in blood in the pH range 6.7 to 8.0, which demonstrates potential for use for in vivo sensing.

Grant, Sheila A.; Glass, Robert S.

1997-06-01

120

Nanostructured Energetci Matreials with sol-gel Chemistry  

SciTech Connect

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

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

2003-11-18

121

Sol-gel polymerization of tetraalkoxygermanium and organotrialkoxygermanium monomers  

SciTech Connect

While the sol-gel polymerizations of tetraalkoxy- and organotrialkoxysilanes have been extensively studied, there have been few reports of similar investigations with the analogous tetraalkoxygermanium and organotrialkoxygermanium compounds. Germanium alkoxides have received less attention due, in part to their higher cost, but also their greater reactivity towards hydrolysis and condensation reactions. Germanium oxide materials are potentially interesting because the Ge-O-Ge linkage is labile (compared with the siloxane bond in silica gels and polysilsequioxanes) opening up the possibility of further chemical modification of the polymeric architecture. This may permit hydrolytic reorganization of germanium oxide networks under relatively mild conditions. In this paper, the authors present the results of investigations of the sol-gel polymerizations of tetraethoxygermanium, tetraisopropoxygermanium, and methyltriethoxy-germanium to afford network materials as both xerogels and aerogels.

Baugher, B.M.; Loy, D.A. [Sandia National Labs., Albuquerque, NM (United States). Properties of Organic Materials Dept.

1996-12-31

122

Optical detection of parasitic protozoa in sol-gel matrices  

NASA Astrophysics Data System (ADS)

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

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

1994-10-01

123

Sol-gel-based, planar waveguide sensor for gaseous iodine.  

PubMed

A novel sensor for gaseous iodine has been developed using a combination of sol-gel processing and planar integrated optical waveguiding technologies. The sensing principle is based on the detection of a charge transfer complex formed between iodine and phenyl groups that have been incorporated into a porous, methylated glass film. The glass film was prepared from siloxane precursors by the sol-gel method. Sensors were fabricated by coating the film over a single-mode planar waveguide. Light was coupled into and out of the laminate structure using integral grating couplers, and formation of the charge transfer complex was monitored as attenuated total reflection of the guided wave. The sensor exhibits a linear response to I(2) in the range of 100 ppb to 15 ppm with response and recovery times less than 15 s. The response is selective to 4 ppm iodine in the presence of 10 ppm chlorine and is stable for at least 3 months. PMID:21619094

Yang, L; Saavedra, S S; Armstrong, N R

1996-06-01

124

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

Microsoft Academic Search

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

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

125

New developments for sol-gel film and fiber processing  

SciTech Connect

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

Hurd, A.J.

1995-03-01

126

Sol-Gel Insulation Coatings on Wires for Coil Development  

Microsoft Academic Search

In this study, preparation, structure, morphology and thermal properties of ceramic insulation coating on Monel\\/Fe\\/MgB2 wires, which were fabricated by Hyper Tech Research Inc., using Continuous Tube Forming and Filling (CTFF) process were studied for coil development. Ceramic insulation coatings were prepared by reel-to-reel sol-gel method using solutions of Y and Zr based organometallic compounds. The coating thickness was controlled

L. Arda; C. Boyraz; O. A. Sacli; M. Tomsic; Y. S. Hascicek

2008-01-01

127

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

128

Sol-Gel materials for optical waveguide applications  

NASA Astrophysics Data System (ADS)

Sol-gel materials are an important material class, as they provide for easy modification of material properties, good processability and routine synthesis. This allows for the tailoring of the material properties to the needs of specific device designs. In the case of electro-optic modulators with a coplanar or coplanar strip (CPS) electrode design, sol-gel cladding materials can be used to confine the light to the electro-optic material as well as to concentrate the electrical field used for poling and driving the modulator. Another important material property that can influence the poling efficiency is the conductivity of the material surrounding the electro-optic material, and this property can also be controlled. In this dissertation I discuss several approaches to altering the material properties of sol-gel materials in order to achieve a specific performance objective. The optical loss in the telecom regime as well the refractive index will be discussed. I will introduce a novel titania-based family of sol-gel materials, which exhibit very high refractive indices, tuneability and high dielectric constant (epsilon). Coplanar electrode design is useful for device platforms that do not allow for a microstrip geometry, such as silicon and Si3N 4 devices. CPS electrodes however bring new challenges with them, especially optimizing the poling process. I will discuss a method for characterizing coplanar poled polymer films by a modified Teng-Man technique as well as with second harmonic microscope (SHM). SHM allows for an almost real-time mapping of the Pockels coefficient. The described method allows for quantitative measurements of the Pockels coefficient in a poled film with spatial resolution at the micron level. Finally, I will discuss the device design considerations for a silicon-EO hybrid modulator. Optimal dimensions for the silicon waveguide are shown and the feasibility of the proposed electrode design for high speed operation is theoretically shown. All design parameters, including electrode spacing and height are optimized towards the highest possible figure of merit. The functionality of a simple test device is shown. For Si3N 4 waveguides optimal dimensions are found as well and the influence of a high epsilon sol-gel side cladding is examined.

Himmelhuber, Roland

129

Sol-gel kinetics: /sup 29/SI NMR and a statistical reaction model  

SciTech Connect

Sol-gel processes allow one to prepare novel materials at low processing temperatures. A detailed understanding of the chemical kinetics of such systems is important to fully exploit the unique features of sol-gel processing. This paper describes a systematic approach to the study of sol-gel kinetics which employs /sup 29/Si NMR spectroscopy and kinetic modelling techniques. 2 figs., 1 tab.

Assink, R.A.; Kay, B.D.

1988-01-01

130

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

SciTech Connect

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

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-04-04

131

Size effects in magnetotransport in sol-gel grown nanostructured manganites  

NASA Astrophysics Data System (ADS)

We report the results of the studies on polycrystalline nanostructured La0.7Pb0.3MnO3 (LPMO) manganites synthesized using sol-gel method employing metal acetate precursor route. Interestingly, it is observed that crystallite size decreases with increase in sintering temperature while microscopic investigations reveal the second grain growth in all the samples. A correlation between the grain morphology and secondary grain growth with the transport and magnetotransport in LPMO manganites has been established. Observation of large temperature sensitivity (~-28.29 %/K @ 0 T; >300 K) and field sensitivity (~-48.70 %/T @ 0.2 T; 5 K) in the samples sintered at higher temperature (~1150 °C) has been understood in the light of observed secondary grain growth in the form of nanosized grains over the surface of primary grains.

Shah, N. A.; Solanki, P. S.; Ravalia, Ashish; Kuberkar, D. G.

2015-02-01

132

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

133

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

134

Modified sol-gel coatings for biotechnological applications  

NASA Astrophysics Data System (ADS)

The modified sol-gel derived silica coatings were prepared and characterized. The amino and methyl groups were introduced onto the colloidal silica. The silica coatings with different wettability properties: coloidal silica (water contact angle 17°), polysiloxane (61°), methyl-modified (158° and 46°) coatings samples were tested for CaCo-2 cells proliferation. Methyl-modified coating (46°) proved to be the best substrate for cell proliferation. CaCo-2 cell proliferation two days post seeding was significantly faster on almost laminine, fibronectin and collagen-1 coated samples compared to corresponding controls.

Beganskiene, A.; Raudonis, R.; Zemljic Jokhadar, S.; Batista, U.; Kareiva, A.

2007-12-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

136

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

137

Preparation of superhydrophobic surface with a novel sol-gel system  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

138

Surfactant based sol–gel approach to nanostructured LiFePO 4 for high rate Li-ion batteries  

Microsoft Academic Search

Porous nanostructured LiFePO4 powder with a narrow particle size distribution (100–300nm) for high rate lithium-ion battery cathode application was obtained using an ethanol based sol–gel route employing lauric acid as a surfactant. The synthesized LiFePO4 powders comprised of agglomerates of crystallites <65nm in diameter exhibiting a specific surface area ranging from 8m2g?1 to 36m2g?1 depending on the absence or presence

Daiwon Choi; Prashant N. Kumta

2007-01-01

139

Photoconductivity for silver nitrate in nanostructured sol-gel materials.  

PubMed

We report on the photoconductive response of nanostructured sol-gel films in function of the silver nitrate concentration (ions and colloids). Silver colloids were obtained by spontaneous reduction process of Ag+ ions to Ag(0). 2-d hexagonal nanosructured 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 optical absorption band located at 430 nm was detected by optical absorption; it corresponds to the surface plasmon. A fit to this band with modified Gans theory is presented. Photoconductivity studies were performed on films with silver ions and films with silver colloids to characterize their mechanisms of charge transport in the darkness and under illumination at 420 and 633 nm wavelengths. The films with silver colloids exhibit a photovoltaic effect stronger than the films with silver ions. While a photoconductive behaviour is observed in the films with silver ions. PMID:19205242

Franco, Alfredo; Rentería, Victor; Valverde-Aguilar, Guadalupe; García-Macedo, Jorge A

2008-12-01

140

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

141

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

142

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

143

Development of sol-gel formulations for slow release of phermones  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new type of dispenser for slow-release of semiochemicals and sex pheromones was developed based on sol-gel polymers that can be useful in monitoring, mass trapping, and mating disruption in integrated pest management (IPM). Sol-gel matrices exhibit glass characteristics and allow control of the de...

144

Visualizing Chemical Compositions and Kinetics of Sol-Gel by Near-Infrared Multispectral Imaging  

E-print Network

Visualizing Chemical Compositions and Kinetics of Sol-Gel by Near-Infrared Multispectral Imaging, Milwaukee, Wisconsin 53201 Kinetics of sol-gel formation were studied using the recently developed near-infrared been studied extensively by many different spectroscopic techniques.4-15 Among them, the near-infrared

Reid, Scott A.

145

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); Ingram, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor)

2010-01-01

146

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

147

Synthesis, functionalisation and characterisation of mesoporous materials and sol–gel glasses for applications in catalysis, adsorption and photonics  

Microsoft Academic Search

In this review, synthesis and functionalisation approaches for ordered mesoporous materials and sol–gel glasses are described. Catalytic and adsorption applications are emphasised for the ordered mesoporous materials, while optical applications are the focus for sol–gel glasses.

Gisle Øye; Wilhelm R. Glomm; Torbjørn Vrålstad; Sondre Volden; Heléne Magnusson; Michael Stöcker; Johan Sjöblom

2006-01-01

148

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

NASA Astrophysics Data System (ADS)

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

Li, Ying-Sing

2012-10-01

149

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

150

Sol-gel derived nanoporous compositions for entrapping small molecules and their outlook toward aptamer screening.  

PubMed

This paper reports for the first time the application of sol-gel microarrays for immobilizing nonsoluble small chemicals (Bisphenol-A; BPA). Also, known problems of sol-gel adhesion to conventional microtiter well plate substrates are circumvented by anchoring the sol-gel microspots to a porous silion surface so-called, PS-SG chips. We confirmed low molecular weight chemical immobilization inside a sol-gel network using fluorescein. BPA and the BPA specific aptamer were utilized as a model pair to verify the affinity specific interaction in the PS-SG selection system. The aptamer interacted specifically with BPA in the sol-gel spots, as shown in microarrays forming the letters "L", "U", "N", and "D". Moreover, the bound aptamer was released by heat, recovered, and verified by gel electrophoresis. The developed PS-SG chip platform will be used for screening aptamers against numerous small molecules such as toxins, metabolites, or pesticide residues. PMID:22283623

Ahn, Ji-Young; Lee, SangWook; Jo, Minjoung; Kang, Jeehye; Kim, Eunkyung; Jeong, Ok Chan; Laurell, Thomas; Kim, Soyoun

2012-03-20

151

Preparation and characterization of sol–gel derived glasses in the ternary Na 2 O–Al 2 O 3 –P 2 O 5 system  

Microsoft Academic Search

A new sol–gel synthesis route to organic free Na2O–Al2O3–P2O5 xerogels was developed. These xerogels contain P2O5 up to 67.5 mole % and Al2O3 up to 20 mole % and could be melted to homogeneous glasses in air at significantly lower temperatures than those applied using the conventionally melting method. Aluminum isopropoxide dissolved in isopropanol, orthophosphoric acid dissolved in isopropanol and

Sherief M. Abo-Naf; N. A. Ghoneim; H. A. EI-Batal

2004-01-01

152

Magnetic properties of Ba-M-type hexagonal ferrites prepared by the sol–gel method with and without polyethylene glycol added  

Microsoft Academic Search

Ba-M-type hexagonal ferrites have been prepared via a sol–gel route, and the effects of adding different amounts of polyethylene glycol (PEG 2000) into the sol solutions on their static magnetic properties and particle morphologies also have been studied. With increasing the amount of PEG added, it is found that both the saturation magnetization and the coercivity decreases. The magnetocrystalline anisotropy

Mangui Han; Yu Ou; Wenbing Chen; Longjiang Deng

2009-01-01

153

Fabrication of hybrid sol-gel glass diffractive elements  

NASA Astrophysics Data System (ADS)

Organically modified photosensitive hybrid glasses are synthesized and used for the fabrication of diffractive optical elements. The material synthesis is based on a sol-gel process. The materials are spin-deposited onto glass substrate that also have a significant role in the component assembly. The synthesized material has a negative tone property under UV-radiation and they can be patterned by a conventional UV- lithography process. Binary diffractive lenses are photoimprinted through an amplitude contact mask. Optical properties and surface roughness of the materials and elements are evaluated. Diffraction efficiencies of the elements are also measured. The process and material optimization for the reliable fabrication of integrated optics devices is carried out.

Rantala, Juha T.; Ayras, Pekka; Levy, Raviv; Descour, Michael R.; Honkanen, Seppo; Peyghambarian, Nasser

1999-03-01

154

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

155

Raman Studies of the Nanostructure of Sol-Gel Materials  

NASA Astrophysics Data System (ADS)

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

Doss, Calvin James

156

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

157

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

158

Fabrication of high density UO 2 fuel pellets involving sol-gel microsphere pelletisation and low temperature sintering  

NASA Astrophysics Data System (ADS)

Powder-free sol-gel microsphere pelletisation and low temperature (1473 K) oxidative sintering processes were used in combination for fabrication of high density (? 96% TD) UO 2 fuel pellets for pressurised heavy water reactors. The "internal gelation of uranium" process of BARC was modified for preparation of hydrated gel-microspheres of UO 3 containing "carbon black" pore former. The gel-microspheres were subjected to controlled air-calcination at 973 K, followed by hydrogen reduction to obtain porous, dust-free and free-flowing UO 2 microspheres suitable for direct pelletisation at 225 MPa. Oxidative sintering of these pellets at 1473 K in CO 2 atmosphere followed by Ar+H 2 treatment led to high density (?96%TD) UO 2 pellets having equiaxed grains of < 10 ?m and uniformly distributed "closed" spherical pores in the diameter range of 2-5 ?m. Resintering of these pellets at high temperature (1973 K) for 8 hours in Ar+8% H 2 atmosphere did not show any significant change in pellet dimension or grain size. The UO 2 pellets prepared by sol-gel microsphere pelletisation route had higher thermal conductivity compared to pellets of equivalent density prepared by the "powder-pellet" route. UO 2 pellets of large grain size (45-55 ?m) and high density could be obtained with TiO 2 dopant and high temperature sintering in Ar+H 2 atmosphere. TiO 2 dopant was not effective for low temperature oxidative sintering.

Ganguly, C.; Basak, U.

1991-02-01

159

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

PubMed

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

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

2012-05-01

160

Sol-gel synthesis, characterization and luminescence properties of SrMgAl2 SiO7:Eu2+ as a novel nanocrystalline phosphor.  

PubMed

In this research, a new SrMgAl(2) SiO(7):Eu(2+) phosphor was synthesized via the sol-gel method. The phase-forming processes were studied by thermogravimetric-differential thermal analysis and X-ray diffraction technique. Scanning electron microscopy showed that there is uniform morphology and microstructure owing to the sol-gel route. Spectrophotometry and colorimetry analyses illustrated that, under short ultraviolet excitation, the main emission peak occurred at 421 nm and also a relatively pure blue color was observed that was ascribed to the 4f(6) 5d(1) ((2) D) ? 4f(7) ((8) S(7/2)) transition of Eu(2+) with color coordination of x = 0.187, y = 0.077. Finally, it was found that the color and phase purity of the synthesized powder increased as calcinations time increased. PMID:20928926

Salimi, R; Sameie, H; Alvani, A A Sabbagh; Sarabi, A A; Moztarzadeh, F; Tahriri, M

2011-01-01

161

Heat treatment effect on the physical properties of cobalt doped TiO{sub 2} sol–gel materials  

SciTech Connect

Cobalt doped and undoped TiO{sub 2} powders have been prepared by sol–gel technique and annealed at temperatures ranging from 400 °C to 1000 °C. The effects of annealing temperature on the structural, morphological and optical properties have been characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy and diffuse reflectance spectroscopy. For all doped samples there is a general reduction of the band gap energy, in comparison with undoped samples prepared in the same conditions. More specifically, experimental results indicate that cobalt doping, occurring as Co{sup 2+} ion insertion into the TiO{sub 2} (Ti{sup 4+}) host lattice, inhibits the growth of the crystallites and delays the phase transformation from anatase to rutile. Moreover, at high temperature, a secondary phase (CoTiO{sub 3}) is found to coexist with highly crystalline rutile. These structural characteristics are discussed in relation with the observed general trends for the optical properties. - Highlights: • Cobalt doped and undoped TiO{sub 2} powders have been prepared by sol–gel route. • Doping makes the band gap narrower. • Doping delays the phase transformation from anatase to rutile. • Doping inhibits the growth of the crystallites. • At high annealing temperature a CoTiO{sub 3} phase coexists with highly crystalline rutile.

Samet, L., E-mail: lolwasamet@gmail.com [Institut Préparatoires aux Etudes d'Ingénieurs d'El-Manar, Université Tunis El Manar, Campus Universitaire, 2092 El Manar (Tunisia); Laboratoire de Photovoltaique de Semi-conducteur et de Nanostructure, Centre de Recherches et des Technologies de l'Energie, Technopole borj cedria, Bp 95, hammamm lif 2050 (Tunisia); Ben Nasseur, J.; Chtourou, R. [Laboratoire de Photovoltaique de Semi-conducteur et de Nanostructure, Centre de Recherches et des Technologies de l'Energie, Technopole borj cedria, Bp 95, hammamm lif 2050 (Tunisia); March, K.; Stephan, O. [Laboratoire de Physique des Solides, UMR 8502 CNRS - Université Paris-Sud, Bât 510, 91405 Orsay cedex (France)

2013-11-15

162

Calcium phosphate sol-gel-derived coatings on titanium-aluminum-vanadium substrate for biomedical applications  

NASA Astrophysics Data System (ADS)

Osseointegration of implants to host bone is a necessary requirement for dental and orthopaedic implants. The rate and quality of osseointegration were enhanced through the use of calcium phosphate (Ca-P) films on metallic substrates. The present study investigates the characteristics of Ca-P films applied using sol-gel dip coating methods to sintered porous-surfaced implants. Ca-P films have been formed using Inorganic Route and Organic Route processes. It has been shown that both approaches resulted in the formation of carbonated hydroxyapatite but with different Ca/P ratios as well as different surface textures and film structures, the Inorganic Route-formed film being more porous at its outermost surface, and having a more irregular topography. An interfacial reaction product (calcium titanium oxide) was detected for the Inorganic Route-formed coatings while this interfacial phase was not detectable in the Organic Route-formed coatings. The interface tensile and shear adhesion strength properties of Ca-P films have been evaluated using an improved direct pull-off testing (ASTM C633) and a substrate straining method, respectively. For both Ca-P films, the adhesive tensile strength was higher than the failure stress of ˜38 MPa occurring between the Ca-P films and the glue or in the glue. A shear lag approach revealed a shear strength of 347 +/- 64MPa and 280 +/- 28MPa for the Inorganic Route and the Organic Route Ca-P films, respectively. In vivo animal model studies have been performed to compare the effect on early bone formation of sintered porous-surfaced implants that had been modified through the addition of Ca-P film. In Group I study (i.e. Inorganic Route-formed Ca-P-coated implants vs. non-coated implants), it has been found that the Inorganic Route-formed Ca-P film significantly enhances the early rate of bone ingrowth for sintered porous-surfaced implants. However, in Group II study (i.e. Organic Route-formed Ca-P-coated implants vs. non-coated implants), significant improvement was not observed for the Organic Route-formed Ca-P film. It is speculated that the slightly different surface topography and film density between the two Ca-P films result in a different amounts of protein adsorption on the implant surface at the early stage, which further affects the following processes leading to osseointegration.

Gan, Lu

163

Optical pH detector based on LTCC and sol-gel technologies  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

164

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

165

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

166

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

167

Fabrication of ceramic microspheres by diffusion-induced sol-gel reaction in double emulsions.  

PubMed

We demonstrate an approach to prepare zirconium dioxide (ZrO2) microspheres by carrying out a diffusion-induced sol-gel reaction inside double emulsion droplets. A glass capillary microfluidic device is introduced to generate monodisperse water-in-oil-in-water (W/O/W) double emulsions with a zirconium precursor as the inner phase. By adding ammonia to the continuous aqueous phase, the zirconium precursor solution is triggered to gel inside the emulsions. The double emulsion structure enhances the uniformity in the rate of the sol-gel reaction, resulting in sol-gel microspheres with improved size uniformity and sphericity. ZrO2 ceramic microspheres are formed following subsequent drying and sintering steps. Our approach, which combines double-emulsion-templating and sol-gel synthesis, has great potential for fabricating versatile ceramic microspheres for applications under high temperature and pressure. PMID:23865771

Zhang, Lei; Hao, Shaochang; Liu, Bing; Shum, Ho Cheung; Li, Jiang; Chen, Haosheng

2013-11-27

168

Investigation of the sol-gel transition of gelatin using terahertz time-domain spectroscopy  

NASA Astrophysics Data System (ADS)

The sol-gel transition temperature of gelatin is determined using viscoelasticity measurement and terahertz time-domain spectroscopy. From the results of the viscoelasticity measurement, the sol-gel transition temperature is determined to be 30-32 °C, and it strongly depended on the concentration. However, terahertz time-domain spectroscopy indicates a particular transition temperature of 36 °C. A distinction of these transition temperatures is attributed to the difference in the structural changes detected by these measurements.

Kawabe, Shunsuke; Seki, Munetoshi; Tabata, Hitoshi

2014-04-01

169

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

170

Development of sol–gel formulations for slow release of pheromones  

Microsoft Academic Search

A new type of dispenser for slow-release of sex pheromones and other semiochemicals was developed based on sol–gel polymers\\u000a that can be useful for monitoring, mass trapping, and mating disruption in integrated pest management (IPM). Sol–gel matrices\\u000a exhibit glass characteristics and allow control of the degree of cross-linking during the polymerization process in order\\u000a to provide an optimal release rate

Anat Zada; Lily Falach; John A. Byers

2009-01-01

171

Fabrication of superhydrophobic sol–gel composite films using hydrophobically modified colloidal zinc hydroxide  

Microsoft Academic Search

A superhydrophobic sol–gel composite film was fabricated by incorporating hydrophobically modified colloidal zinc hydroxide (CZH) in sol–gel matrix. CZH was prepared by controlled precipitation and modified by treatment with stearic acid. The concentration of stearic acid and stirring time were optimized to obtain modified CZH with very high water contact angle (WCA) of 165° and sliding angle (SA)<2°. X-ray diffraction

R. V. Lakshmi; Bharathibai J. Basu

2009-01-01

172

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

Microsoft Academic Search

The sol-gel method is applied to prepare γ-alumina-supported copper oxide and calcium oxide sorbents containing 10--50 wt% active species. The prepared sorbents are characterized for their pore texture, dispersion of active species on the surface of support, and desulfurization properties. The sol-gel-derived alumina-supported sorbents have a relatively large surface area (> 200 m²\\/g) and pore volume (> 0.3 cm³\\/g) and

S. G. Deng; Y. S. Lin

1996-01-01

173

Hard-tissue-engineered zirconia porous scaffolds with hydroxyapatite sol-gel and slurry coatings  

Microsoft Academic Search

A zirconia (ZrO2) porous scaffold was coated with a gradient apatite layer to induce osteoconductivity with the use of a combination of sol- gel and powder slurry methods. The ZrO2 was used to impart mechanical strength and the apatite layer was coated for functional biocompatibility. The coating layer, from the outside in, was composed of sol- gel hydroxyapatite (HA)\\/slurry HA\\/slurry

Hae-Won Kim; Hyoun-Ee Kim; Jonathan C. Knowles

2004-01-01

174

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

Microsoft Academic Search

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

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

2009-01-01

175

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

Microsoft Academic Search

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

Farid R. Zaggout

2006-01-01

176

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

Microsoft Academic Search

Yttrium iron garnets and Bi-substituted yttrium iron garnets were prepared by two different sol–gel processes. We investigated the evolution with temperature of XRD patterns and of the magnetisation of powders issued from sol–gel solution decomposition. We prepared layers on silica glass by the spin- or dip-coating processes. XRD patterns on layers were also obtained. The dependency of the Faraday effect

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

2000-01-01

177

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

178

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

179

Controlled release of vancomycin from thin sol-gel films on implant surfaces successfully controls osteomyelitis.  

PubMed

Peri-prosthetic infection remains a serious complication of joint replacement surgery. Herein, we demonstrate that a vancomycin-containing sol-gel film on Ti alloy rods can successfully treat bacterial infections in an animal model. The vancomycin-containing sol-gel films exhibited predictable release kinetics, while significantly inhibiting S. aureus adhesion. When evaluated in a rat osteomyelitis model, microbiological analysis indicated that the vancomycin-containing sol-gel film caused a profound decrease in S. aureus number. Radiologically, while the control side showed extensive bone degradation, including abscesses and an extensive periosteal reaction, rods coated with the vancomycin-containing sol-gel film resulted in minimal signs of infection. MicroCT analysis confirmed the radiological results, while demonstrating that the vancomycin-containing sol-gel film significantly protected dense bone from resorption and minimized remodeling. These results clearly demonstrate that this novel thin sol-gel technology can be used for the targeted delivery of antibiotics for the treatment of periprosthetic as well as other bone infections. PMID:19051247

Adams, Christopher S; Antoci, Valentin; Harrison, Gerald; Patal, Payal; Freeman, Terry A; Shapiro, Irving M; Parvizi, Javad; Hickok, Noreen J; Radin, Shula; Ducheyne, Paul

2009-06-01

180

Preparation and antioxidant capacity of element selenium nanoparticles sol-gel compounds.  

PubMed

This paper reported the preparation and antioxidant capacities of element selenium nanoparticles (nanoSe(0))-ascorbic acid (Vc) sol and nanSe(0)/Vc/selenocystine (SeCys) sol-gel compounds. NanoSe(0)-Vc sol was prepared by reduction of selenious dioxide (SeO2) with Vc. In the nanoSe(0)-Vc sol, highly concentrated Vc was also used as a modifier to modulate the diameter of Se(0) nanoparticles in the liquid phase. Then excellent nanoSe(0) sol-gel compounds were obtained by adding SeCys into the nanoSe(0)-Vc sol. The structure of the nanoSe(0)/Vc/SeCys sol-gel compounds was defined, which was constructed via C-Se, Se-H and O=C-Se valences and by interaction between SeCys and Vc via peptide bonds, esterification and dehydration. The antioxidant capacities of the nanoSe(0)-Vc sol and the nanoSe(0)Vc/SeCys sol-gel compounds were estimated by oxygen radical absorption capacity (ORAC) assay. The nanoSe(0)/Vc/SeCys sol-gel compounds possessed a strong antioxidant capacity due to forming the perfect three-dimensional (3D) frameworks structure. The results suggested that the nanoSe(0)-Vc sol and the nanoSe(0)Vc/SeCys sol-gel compounds might be potential medicine, especially antioxidant. PMID:21770136

Bai, Yan; Qin, Biyin; Zhou, Yanhui; Wang, Yudong; Wang, Zi; Zheng, Wenjie

2011-06-01

181

Control of porosity in SiO2:PDMS polycerams through variations in sol-gel processing and polymer content  

NASA Astrophysics Data System (ADS)

A series of optically transparent SiO2: polydimethylsiloxane (PDMS) polyceram monoliths have been synthesized by two-step acid/base sol-gel processes. Two different processing routes are discussed and compared; one synthetic route (Route 1) utilizes lower water content, shorter reflux times, and faster drying conditions compared to the other synthetic route (Route 2). The Route 1 polycerams were all essentially non-porous at all PDMS contents examined (20 - 80 volume % PDMS). In contrast, the porosity of the Route 2 polycerams varied dramatically as a function of PDMS content. The surface area and pore volume for a 0% PDMS Route 2 polyceram were 573 m2/gm and 0.59 cm3/gm, respectively; the surface area and pore volume decreased with increasing PDMS content. The amount of porosity within the polycerams is proposed to be controlled by the relative rates of condensation and evaporation during processing and by the amount of PDMS trapped in the pores. This idea is supported by the differences in the drying behavior with processing and by the structural information obtained by magic angle spinning solid-state 29Si NMR of the polyceram monoliths. Quantitative evaluation of the 29Si NMR and porosity data are utilized to formulate structural models of these polycerams. The structural models are then specifically used to describe the effect of porosity on the photostabilization of a laser dye doped within these polyceram monoliths.

Suratwala, Tayyab I.; Davidson, Kevin; Gardlund, Zack; Uhlmann, Donald R.

1997-10-01

182

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

183

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

184

Water-based sol-gel synthesis of hydroxyapatite: process development.  

PubMed

Hydroxyapatite (HA) ceramics were synthesized using a sol-gel route with triethyl phosphite and calcium nitrate as phosphorus and calcium precursors, respectively. Two solvents, water and anhydrous ethanol, were used as diluting media for HA sol preparation. The sols were stable and no gelling occurred in ambient environment for over 5 days. The sols became a white gel only after removal of the solvents at 60 degrees C. X-ray diffraction showed that apatitic structure first appeared at a temperature as low as 350 degrees C. The crystal size and the HA content in both gels increase with increasing calcination temperature. The type of initial diluting media (i.e., water vs. anhydrous ethanol) did not affect the microstructural evolution and crystallinity of the resulting HA ceramic. The ethanol-based sol dip-coated onto a Ti substrate, followed by calcination at 450 degrees C, was found to be porous with pore size ranging from 0.3 to 1 microm. This morphology is beneficial to the circulation of physiological fluid when the coating is used for biomedical applications. The satisfactory adhesion between the coating and substrate suggests its suitability for load-bearing uses. PMID:11396875

Liu, D M; Troczynski, T; Tseng, W J

2001-07-01

185

Sol gel based YAG : Tb3+ or Eu3+ phosphors for application in lighting sources  

NASA Astrophysics Data System (ADS)

Luminescent Y3Al5O12 : Eu3+ (YAG : Eu3+) and Y3Al5O12 : Tb3+ (YAG : Tb3+) powders with nanometre and micrometre-sized particles and films have been successfully synthesized by sol-gel route from alkoxide precursors. Advanced YAG coatings were achieved by spray and dip-coating methods, giving rise to different structural and optical properties. High temperature x-ray diffraction, x-ray powder diffraction, scanning electron microscopy and atomic force microscopy were used to investigate the materials structure and morphology. Pure polycrystalline YAG powder was obtained from 900°C. Laser induced luminescence spectra as well as luminescence decays of Tb3+ and Eu3+ ions were recorded. This study showed, undoubtedly, the spectral features of an Eu3+ emitting centre embedded in a unique site of D2 symmetry. Furthermore, the well-known cross-relaxation phenomenon was observed for Tb3+. Decay times were found to be exponential and shorter than 5 ms for both Eu3+ and Tb3+ activators. Finally, the spectroscopic properties of YAG : Tb3+ powders under vacuum ultra violet excitation were analysed and encouraging results were obtained regarding luminescence efficiency and time constants.

Potdevin, A.; Chadeyron, G.; Boyer, D.; Caillier, B.; Mahiou, R.

2005-09-01

186

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

Microsoft Academic Search

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

Bambang Kuswandi; Chulaifah Indah Fikriyah; Agus Abdul Gani

2008-01-01

187

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

188

Evaluating mechanical adhesion of sol-gel titanium dioxide coatings containing calcium phosphate for metal implant application.  

PubMed

The adhesion of thin (< 10 microm) sol-gel calcium phosphate-titanium dioxide films bonded to a titanium substrate was studied using two different tests: a rotating-bending test and a tensile bond test. The former evaluates the impact of both the coating procedure and the surface pre-treatment on the resistance to fatigue of the substrate as well as the adhesion of the coating; the latter measures the tensile adhesion strength of the coating. Both tests gave similar results. A reduction of the thickness of the coating or an increase of the roughness of the substrate improves the quality of the interface. A comparison of the adhesion of the calcium phosphate-titanium dioxide film with that of a pure calcium phosphate coating obtained by a similar route suggests the involvement of a chemical component in the binding. PMID:10985493

Piveteau, L D; Gasser, B; Schlapbach, L

2000-11-01

189

Sol-gel process from heterometallic alkoxides to incorporate alkaline- and rare earths in alumina for automotive applications  

SciTech Connect

The high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, the authors briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. They will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

Narula, C.K. [Ford Motor Co., Dearborn, MI (United States). Dept. of Chemistry

1996-12-31

190

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

PubMed

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

Li, Ying-Sing

2012-10-01

191

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

192

Sol-gel derived erbium doped yttrium silicates  

NASA Astrophysics Data System (ADS)

Yttria-silica gels were prepared through the sol-gel process. Gels of compositions (100-5x) SiO2-4xY2O3-xEr 2O3 (x = 0.05, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0), all in mole %, were prepared. Samples were designated SYEz, where z = 100--5x. Samples with co-doping ratios [Y3+]:[Er3+] equal to 4, 150 and 200 were prepared for a 0.05 mol.% Er2O3 composition. In addition, samples corresponding to nominal compositions of (Y/Er)2Si2O7 and (Y/Er)2SiO 5 were synthesized. Dried gels were densified to glasses and glass-ceramics, through controlled heat treatment. Heat treatment schedules and densification temperatures were chosen based on thermal analyses (DTA, TGA). Phase-separation and crystallization were followed using X-Ray diffraction analysis on powders of heat-treated samples. Optical properties of the samples were studied by UV-VIS-NIR absorption, photo-luminescence (PL) and time-resolved spectroscopic techniques and were correlated with microstructure. Radiative and non-radiative properties of the densified samples at 1535 nm were studied by correlating the absorption and time-resolved spectral data with standard theoretical methods. Samples with greater than 90 mol.% SiO2 densified to form transparent glasses before crystallization. Samples containing less than 90 mol.% SiO2 crystallized before densification. The tendency to crystallize depends on the total trivalent addition (Y2O3 + Er 2O3) and not on the ratio of Y:Er. Samples containing the lowest trivalent content (SYE99-0.25 mol.%) remained amorphous up to 1200°C and produced the longest lifetime measured, 13.3 ms. No evidence for concentration quenching was observed. The highest value of PL quantum efficiency obtained was 73.1%. In phase-separated samples, the PL decay lifetime increased with increasing Y:Er ratio and increasing temperature of heat treatment. After annealing at 1300°C, the lifetime measured for the highest Y:Er ratio of 200:1 (SYE89) was 10.0 ms and 3.3 ms for a ratio of 4:1 (SYE90). At high Y:Er ratios (>150:1), the main non-radiative decay mechanism is multi-phonon relaxation. Energy transfer mechanism becomes dominant as the ratio decreases (4:1). OH quenching is found to affect optical activity of Er ions in the amorphous phase.

Ranganathan, Varadharajan

193

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

PubMed

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

Bagheri, Habib; Piri-Moghadam, Hamed

2012-09-01

194

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

SciTech Connect

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

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

2005-01-31

195

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

196

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

SciTech Connect

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

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

2012-06-18

197

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

198

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

NASA Astrophysics Data System (ADS)

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

Lobnik, Aleksandra; Niederreiter, Karlheinz; Uray, Georg

1999-11-01

199

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

PubMed

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

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

2012-08-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

201

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

NASA Astrophysics Data System (ADS)

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

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

202

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

203

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

204

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

SciTech Connect

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

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

2000-04-25

205

Novel Sol-Gel Based Pt Nanocluster Catalysts for Propane Dehydrogenation  

SciTech Connect

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

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

1999-08-09

206

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

207

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

208

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

PubMed

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

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

2012-02-01

209

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

Microsoft Academic Search

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

Zhong-Min Wang; Y. S. Lin

1998-01-01

210

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

211

Sol-gel processed alumina based materials in microcalorimeter sensor device fabrication for automotive applications  

SciTech Connect

The application of sol-gel processed materials in a variety of sensors has been proposed. The authors describe microcalorimeter sensor devices employing sol-gel processed alumina based materials which can be used to monitor pollutants in automotive exhaust. These sensors operate by measuring changes in resistance upon catalysis and are economically acceptable for automotive applications. It is important to point out that automobiles will be required to have a means of monitoring exhaust gases by on-board sensors as mandated by the EPA and the California Air Resources Board (OBD-II).

Nakouzi, S.R.; McBride, J.R.; Nietering, K.E.; Narula, C.K. [Ford Motor Co., Dearborn, MI (United States)

1996-12-31

212

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

PubMed

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

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

2013-10-01

213

Sol-gel-derived prussian blue-silicate amperometric glucose biosensor.  

PubMed

A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction of hydrogen peroxide by the Prussian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated. PMID:11209464

Bharathi, S; Lev, O

2000-01-01

214

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

215

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...

216

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

217

JOURNAL OF MATERIALS SCIENCE LETTERS 21, 2002, 251 255 Organic-inorganic sol-gel coating for corrosion protection  

E-print Network

(Cr2O3) passivation layer formed on the surface of stainless steel in oxi- dizing environments is one protection of stainless steel [9­13]. In spite of all the advantages of sol-gel processing, sol-gel oxide for corrosion protection of stainless steel T. P. CHOU Department of Materials Science and Engineering

Cao, Guozhong

218

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

Microsoft Academic Search

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

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

2012-01-01

219

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

220

Surface analysis and biocorrosion properties of nanostructured surface sol–gel coatings on Ti6Al4V titanium alloy implants  

Microsoft Academic Search

Surfaces of biocompatible alloys used as implants play a significant role in their osseointegration. Surface sol- gel processing (SSP), a variant of the bulk sol- gel technique, is a relatively new process to prepare bioreactive nanostructured titanium oxide for thin film coatings. The surface topography, roughness, and composition of sol- gel processed Ti6Al4V titanium alloy coatings was investigated by atomic

Maria C. Advincula; Don Petersen; Firoz Rahemtulla; Rigoberto Advincula; Jack E. Lemons

2007-01-01

221

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

PubMed

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

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

2013-01-01

222

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

223

Preparation and characterization of cerium doped silica sol–gel coatings on glass and aluminum substrates  

Microsoft Academic Search

Chromates are among the most common substances used as corrosion inhibitors. However, these compounds are highly toxic, and an intense effort is being undertaken to replace them. Cerium compounds seem to fulfil the basic requirements for consideration as alternative corrosion inhibitors. The aim of this work was to study the effect of the incorporation of cerium ions in silica sol–gel

A. Pepe; M. Aparicio; S. Ceré; A. Durán

2004-01-01

224

Investigations into sol-gel silica and silica hybrid coatings for dielectromagnetic soft magnetic composite applications  

Microsoft Academic Search

A series of inorganic and organic–inorganic hybrid silica coatings were synthesised by a sol-gel process from tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) precursors, and used to investigate their effectiveness as insulation materials in dielectromagnetic soft magnetic composites. The coating materials and coated iron powders were analysed by FTIR, electron and atomic force microscopy. Results showed that introduction of the organic phase

Y. X. Pang; S. N. B. Hodgson; B. Weglinski; D. Gaworska

2006-01-01

225

Study of the reactions in preparing ultrafine KTN powders by sol—gel method  

Microsoft Academic Search

This paper reported the ractions in preparing ultrafine KTN powders by Sol—Gel method, and discovered that. In the heat treatment process, Gel not only occured the carbonized, oxidized reactions of ethyoxy and the carbonates formation reactions, but also occured the two intermediate phases formation reactions, the formation reaction of KTN phase in one step, and the reaction that the two

Shimin Wang; Jianhong Zhao; Caojing Lu; Dinhua Bao; Haoshuang Gu; Guiyu Huang; Anxiang Kuang

1994-01-01

226

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...

227

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

E-print Network

on the plastic surface. Nanoindentation analysis revealed that the coatings have a surface hardness up to 2.5 ± 0Nanoindentation and adhesion of sol-gel-derived hard coatings on polyester C.M. Chan, G.Z. Cao,a) H coatings on modified polyester substrates. The silica network was modified by incorporating an organic

Cao, Guozhong

228

Stable doped hybrid sol-gel materials for solid-state dye laser  

E-print Network

Stable doped hybrid sol-gel materials for solid-state dye laser Tran H. Nhung, Michael Canva.3380, 140.3580. 1. Introduction Much research has already been devoted to solid- state dye lasers, because stability, the pyr- romethene dyes are currently the most promising dyes used for solid-state laser

Paris-Sud XI, Université de

229

Sol-Gel-Encapsulated Alcohol Dehydrogenase as a Versatile, Environmentally Stabilized Sensor for Alcohols and Aldehydes  

E-print Network

of exogenous alcohol, a synthetic component often capable of inducing enzyme denaturation.1c,3 The designSol-Gel-Encapsulated Alcohol Dehydrogenase as a Versatile, Environmentally Stabilized Sensor for Alcohols and Aldehydes Amy K. Williams and Joseph T. Hupp* Contribution from the Department of Chemistry

230

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

231

Electronic nose screening of ethanol release during sol–gel encapsulation  

Microsoft Academic Search

Porous silica matrices prepared by sol–gel process yield biocompatible materials adequate for encapsulation of biomolecules or drugs. The procedure is simple and fast, but when alkoxyde precursors like tetraethoxysilane (TEOS) are used the polymerisation reaction leads to the formation of alcohol as a by-product, which can produce undesirable effects on the activity of entrapped enzymes or modify a drug release

Magalí Lovino; M. Fernanda Cardinal; Diana B. V. Zubiri; Delia L. Bernik

2005-01-01

232

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

233

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

234

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

235

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

236

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

237

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

238

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

239

Sol–gel derived hydroxyapatite coatings on titanium and its alloy Ti6Al4V  

Microsoft Academic Search

Titanium has been used for many medical and dental applications; however, its joining to a living bone is not satisfactorily good or the implant integration with bone tissue takes several months.The aim of this work is to produce hydroxyapatite (HAP) coatings on titanium and its alloy for facilitating and shortening the processes towards osseointegration. HAP coatings were obtained by sol–gel

A. Stoch; E. Dlugon; W. Lejda; B. Trybalska; G. J. Stoch; A. Adamczyk

2005-01-01

240

Osteoblast adhesion and matrix mineralization on sol-gel-derived titanium oxide.  

PubMed

The biological events occurring at the bone-implant interface are influenced by the topography, chemistry and wettability of the implant surface. The surface properties of titanium alloy prepared by either surface sol-gel processing (SSP), or by passivation with nitric acid, were investigated systematically using X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and contact angle metrology. The bioreactivity of the substrates was assessed by evaluating MC3T3-E1 osteoblastic cell adhesion, as well as by in vitro formation of mineralized matrix. Surface analysis of sol-gel-derived oxide on Ti6Al4V substrates showed a predominantly titanium dioxide (TiO(2)) composition with abundant hydroxyl groups. The surface was highly wettable, rougher and more porous compared to that of the passivated substrate. Significantly more cells adhered to the sol-gel-coated surface, as compared with passivated surfaces, at 1 and 24h following cell seeding, and a markedly greater number of mineralized nodules were observed on sol-gel coatings. Collectively our results show that the surface properties of titanium alloy can be modified by SSP to enhance the bioreactivity of this biomaterial. PMID:16313951

Advincula, Maria C; Rahemtulla, Firoz G; Advincula, Rigoberto C; Ada, Earl T; Lemons, Jack E; Bellis, Susan L

2006-04-01

241

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

242

Two substrate-confined sol-gel coassembled ordered macroporous silica structures with an open surface.  

PubMed

A sol-gel cooperative assembly method was demonstrated for the fabrication of inverse opal films with an open surface. In this method, a sol-gel silicate precursor was cooperatively assembled into the interstitial spaces of microspheres at the same time when polystyrene templates formed in between two desired substrates. Silica inverse opals with a three-dimensional ordered macroporous (3DOM) structure were obtained after selective removing the colloidal templates by calcination. The open surfaces with a high degree of interconnected porosity and extremely uniform pore size were characterized by scanning electron microscope (SEM). Optical transmission spectra reveals the existence of considerable deep band gaps of up to 70% and steep band edges of up to 6%/nm in the [111] directions of the 3DOM silica samples. A little shrinkage confirmed by transmission spectra is not larger than 3%, in consistent with the results measured by SEM, which revealing the sufficient and compact infiltration into the interstitial spaces by our confined sol-gel coassembly method. With different incidence angles, the positions of pseudogaps can be easily tuned in the wide range from 720 nm to 887 nm, agreed well with the calculated values by the Bragg law. All the results prove that the sol-gel coassembly method with two substrates confinement is a simple, low cost, convenient and versatile method for the fabrication of silica inverse opals without overlayers in large domains. PMID:23614663

Guo, Wenhua; Wang, Ming; Xia, Wei; Dai, Lihua

2013-05-21

243

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.

244

Fabrication and characterization of sol-gel derived 45S5 Bioglass®-ceramic scaffolds.  

PubMed

Although Bioglass® has existed for nearly half a century its ability to trigger bone formation and tuneable degradability is vastly superior to other bioceramics, such as SiO(2)-CaO bioactive glasses. The sol-gel process of producing glass foams is well established for SiO(2)-CaO compositions, but not yet established for 45S5 composites containing Na(2)O. In this work the sol-gel derived 45S5 Bioglass® has for the first time been foamed into highly porous three-dimensional scaffolds using a surfactant, combined with vigorous mechanical stirring and subsequent sintering at 1000°C for 2 h. It was found that the mechanical strength of the sintered sol-gel derived Bioglass® scaffolds was significantly improved, attributable to the small fraction of material on the pore walls. More importantly, the compressive strength of the three-dimensional scaffolds produced by this surfactant foaming method could be predicted using Gibson and Ashby's closed cell model of porous networks. A comparative experiment revealed that ion release from the sol-gel derived Bioglass® foams was faster than that of counterparts produced by the replication technique. In vitro evaluation using osteoblast-like cells demonstrated that the sol-gel derived 45S5 Bioglass foams supported the proliferation of viable cell populations on the surface of the scaffolds, although few cells were observed to migrate into the virtually closed pores within the foams. Further work should be focused on modifications of the reaction conditions or alternative foaming techniques to improve pore interconnection. PMID:21689791

Chen, Qi-Zhi; Thouas, George A

2011-10-01

245

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

246

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

247

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

NASA Astrophysics Data System (ADS)

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 ?m. 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 compositionally flexible routes to high quality optics, we examined solution-based approaches to the synthesis of rare-earth- doped halides that provide luminescence in the 1.3 ?m and 1.55 ?m telecommunication windows. Initial studies into metal-organic-derived, ZBLA fluoride glass thin-films proved the spectroscopic performance of dopants was dominated by nonradiative relaxations caused by the presence of remnant carbonaceous species from the precursors. Heat treatments to above the point of glass devitrification did not resolve this problem and dopant emission remained modified by these extrinsic sources of high energy phonons. Inorganic precursors then were studied to circumvent the issues associated with the residual organics. Amorphous and crystalline single-component halide systems were prepared from aqueous solutions of inorganic chloride salts and their luminescence properties at 1.3 and 1.55 ?m studied. Pr3+- and Dy3+- doped LaF3 and LaCl3 powders were prepared that exhibited 1.3 ?m radiative quantum efficiencies of 72 and 78%, respectively, despite chemical analyses that indicated greater than 2% oxide concentrations. The efficiency values represented the highest measured from any halide to-date. Superiority in spectroscopic performance with respect to melt-grown, single-crystal analogs clearly opposed the widely accepted belief that quantum efficiencies are seriously degraded by precursor purity or the presence of oxygen. The results validated our hypothesis that inexpensive, low temperature, aqueous solution-derived materials can possess low-phonon energies. Luminescence was observed at 1.55 ?m from Er3+-doped LaF3 prepared by a single-step, solution-fluorination method. Available emission bandwidths 360% larger than current optical amplifier materials were realized from highly rare-earth-doped LaF3 transparent gels. The aqueous solution synthesis was found to permit rare-earth solid solubility ranges nearly 50 mole % greater than melt-grown equivalents. This compositional metastability was shown to be process-induced and verified our hypothesis that novel compositional flexibility is enabled by solution- based approaches.

Ballato, John Michael

248

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

249

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

250

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

251

Synthesis of the Nanocrystalline Nickel Ferrite by a Novel Mechano Sol-Gel Auto-Combustion Method  

NASA Astrophysics Data System (ADS)

In this work, a novel method of mechano sol-gel auto-combustion has been developed for production of single phase nickel ferrite nanocrystalline powder, consisting of a sol-gel auto-combustion synthesis followed by a high energy milling process before calcination. Sol-gel auto-combustion was carried out using a gel including citric acid as a reductant and metal nitrates as oxidants. This gel exhibited a self-propagating behavior after ignition in air. The effects of the intermediate high energy milling on the physical properties of the final product after calcination were investigated. The results showed that with a high energy milling of the sol-gel auto-combusted powders with a ball-to-powder mass ratio of 20 for 20 h, the temperature of calcination for synthesis of the single phase ferrite reduced from 1000°C to 700°C and the size of the ferrite crystallites decreased from 72 nm to 15 nm.

Shahmirzaei, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

252

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

PubMed Central

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

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

2014-01-01

253

A Review of Photocatalysts Prepared by Sol-Gel Method for VOCs Removal  

PubMed Central

The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature. PMID:20640156

Tseng, Ting Ke; Lin, Yi Shing; Chen, Yi Ju; Chu, Hsin

2010-01-01

254

Sol-gel synthesis and luminescent properties of nanocrystalline YAP:Mn  

NASA Astrophysics Data System (ADS)

The work describes results of synthesis of Mn-doped YAP nanocrystalline samples by the sol-gel method and characterization of the material by X-ray powder diffraction, scanning electron microscopy and luminescence techniques. It was revealed that obtained in such a way YAP samples posses rather poor radiation storage properties that is interpreted by the uniform near-equilibrium synthesis conditions that does not allow formation of Y Al antisite ions required for electrons trapping. On the other hand, the sol-gel method can be suggested as a suitable technique for obtaining of highly stoichiometric and not defected structure material without parasitic charge capturing and recombination processes that is very essential e.g. for scintillator materials.

Baran, M.; Zhydachevskii, Ya.; Suchocki, A.; Reszka, A.; Warchol, S.; Diduszko, R.; Paj?czkowska, A.

2012-02-01

255

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

256

Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol-gel method  

SciTech Connect

Uniformly distributed nanoparticles of LiCoO{sub 2} have been synthesized through the simple sol-gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge-discharge cycling performance. The powder calcined at a temperature of 900 deg. C for 5 h shows pure phase layered LiCoO{sub 2}. The results show that the particle size is reduced in presence of surfactant as compared to normal sol-gel method. Also, the sample prepared in presence of surfactant and calcined at 900 deg. C for 5 h shows the highest initial discharge capacity (106 mAh g{sup -1}) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g{sup -1}.

Khomane, Ramdas B.; Agrawal, Amit C. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008 (India); Kulkarni, B.D. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008 (India)], E-mail: bd.kulkarni@ncl.res.in; Gopukumar, S. [Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India)], E-mail: deepika_41@rediffmail.com; Sivashanmugam, A. [Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India)

2008-08-04

257

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

258

Anisotropic plasmonic Cu nanoparticles in sol-gel oxide nanopillars studied by spectroscopic Mueller matrix ellipsometry.  

PubMed

Broadened plasmon resonances of Cu nanoparticles in nanopatterned mixed oxide sol-gel nanopillars are shown to be readily detected by spectroscopic Mueller matrix ellipsometry. The plasmonic nanomaterials are obtained by low energy ion sputtering of a CuO sol-gel film. Both s- and p-polarized plasmon resonances are observed in the off-block-diagonal and the block-diagonal Mueller matrix elements as well as in the generalized ellipsometric parameters. The resonant features in all elements correlate with both maximum depolarization and a minimum in the reflected intensity. The spectral position and the polarization character of the plasmon resonances are discussed phenomenologically through effective medium theory. PMID:24514655

Ghadyani, Z; Kildemo, M; Aas, L M S; Cohin, Y; Søndergård, E

2013-12-16

259

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

260

Cross-condensation reactions in an organically modified silica sol-gel  

SciTech Connect

High resolution {sup 29}Si NMR has been used to study the extent of cross condensation taking place in a hybrid organic/inorganic sol-gel system. Tetraethoxysilane (TEOS) and methltriethoxysilane (MTEOS) sol-gels were chosen for this purpose. The sols were prepared by acid catalyzed hydrolysis of TEOS and MTEOS with a H{sub 2}O/Si ratio of 0.3. {sup 29}Si NMR shows signals due to both self-condensation and cross-condensation between TEOS and MTEOS. Resonance assignments were made by comparing the positions and intensities of peaks in the spectra of single and multicomponent systems. It was found that, within experimental error, the self- and cross-condensation rates are equal and that extensive molecular level mixing takes place during the early stages of the reaction.

Prabakar, S.; Raman, N.K. [New Mexico Univ., Albuquerque, NM (United States); Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States); Brinker, C.J. [New Mexico Univ., Albuquerque, NM (United States)]|[Sandia National Labs., Albuquerque, NM (United States)

1993-12-31

261

/sup 1/H NMR studies of the sol-gel transition  

SciTech Connect

High resolution /sup 1/H NMR spectroscopy has been employed to study the dynamics of the sol-gel transition in simple silicates. High magnetic fields (360 MHz) were used to detect and identify the various chemical species present in the Si(OCH/sub 2/CH/sub 3/)/sub 4/:C/sub 2/H/sub 5/OH:H/sub 2/O and Si(OCH/sub 3/)/sub 4/:CH/sub 3/OH:H/sub 2/O sol-gel systems. Using these techniques, the time evolution of the reactant and product species were monitored. Results of these studies have shown that acid and base catalyzed systems react along very different chemical pathways and that the elementary hydrolysis and condensation reactions occur on widely different time scales. The use of these experimental data to test possible mechanisms is discussed.

Assink, R.A.; Kay, B.D.

1984-01-01

262

Sol-gel co-assembly of hollow cylindrical inverse opals and inverse opal columns.  

PubMed

A facile approach of fabricating hollow cylindrical inverse opals and inverse opal columns by sol-gel co-assembly method was proposed. Polystyrene (PS) colloidal suspension added with hydrolyzed silicate precursor solution was used to self-assemble composite colloidal crystals which consist of PS colloidal crystal template and infiltrated silica gel in the interstitial of microspheres. Continuous hollow cylindrical composite colloidal crystal films have been produced on capillaries' outside and internal surface. Composite colloidal crystal columns which filling up the interior of a capillary were fabricated by pressure assisted sol-gel co-assembly method. Hollow cylindrical inverse opals and inverse opal columns were obtained after removing PS colloidal crystal from the composite colloidal crystal. Optical properties of the silica hollow cylindrical inverse opals were characterized by transmission spectrum and a stop band was observed. Structure and optical properties of the inverse opal columns were investigated. PMID:22274178

Haibin, Ni; Ming, Wang; Wei, Chen

2011-12-19

263

Effect of silica precursors-type on mechanical properties of sol-gel coatings.  

PubMed

Reversion to narrowing, called restenosis, still remains an important problem of coronary angioplasty. Analysis of the problem revealed that the application of surface layers aimed at creating on the stent surface a neutral barrier between its metallic framework and tissues of the blood-vascular system is decidedly best to impede the restenosis. They also play the role of medicine carriers. This article presents a new sol-gel technology, to be applied in coronary stent coatings. Currently, this is one of the most progressive methods allowing the modification of surface layers of metallic biomaterials. The results presented prove that due to a proper selection of silica precursors it is possible to obtain continuous, smooth, plastic deformation-resistant sol-gel coatings, which additionally are characterised by very close adherence to the base material, nanometer thickness and low degree of surface development. PMID:18634351

Grygier, Dominika; Dudzi?ski, W?odzimierz; Wiktorczyk, Tadeusz; Haimann, Krystyna

2008-01-01

264

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

265

Synthesis and characterization of boehmitic alumina coated graphite by sol–gel method  

Microsoft Academic Search

Non-wettability property makes graphite a good protecting material against the molten metal and\\/or slag. Properties like high oxidation potential between 600 and 1200°C and non-wettability with water at room temperatures limits the usage of graphite in castable refractory applications. In this study, sol–gel method, which is a relatively cheaper process, was used. Boehmitic sol was obtained by hydrolyzing and peptiziting

Suat Yilmaz; Yasemen Kutmen-Kalpakli; Ersan Yilmaz

2009-01-01

266

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method  

Microsoft Academic Search

Hydroxyapatite (HA) was coated onto a titanium (Ti) substrate with the insertion of a titania (TiO2) buffer layer by the sol–gel method. The HA layer was employed to enhance the bioactivity and osteoconductivity of the Ti substrate, and the TiO2 buffer layer was inserted to improve the bonding strength between the HA layer and Ti substrate, as well as to

Hae-Won Kim; Young-Hag Koh; Long-Hao Li; Sook Lee; Hyoun-Ee Kim

2004-01-01

267

Osteoblast adhesion and matrix mineralization on sol–gel-derived titanium oxide  

Microsoft Academic Search

The biological events occurring at the bone–implant interface are influenced by the topography, chemistry and wettability of the implant surface. The surface properties of titanium alloy prepared by either surface sol–gel processing (SSP), or by passivation with nitric acid, were investigated systematically using X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and contact angle metrology. The bioreactivity of the

Maria C. Advincula; Firoz G. Rahemtulla; Rigoberto C. Advincula; Earl T. Adae; Jack E. Lemons; Susan L. Bellis

2006-01-01

268

Development of novel sol-gel indicators (SGI`s) for in-situ environmental measurements  

SciTech Connect

Organic indicator molecules have been incorporated in a porous sol- gel matrix coated on the end of a fiber-optic lens assembly to create sensors for in situ environmental measurements. Probes have been made that are sensitive to pH and uranyl concentration. The use of fiber optics allows the probe to be lowered into a well or bore hole, while support equipment such as a spectrophotometer and computer may be situated hundreds of meters away.

Livingston, R.R.; Wicks, G.G.; Baylor, L.C.; Whitaker, M.J.

1993-10-01

269

Imprinted sol–gel materials for monitoring degradation products in automotive oils by shear transverse wave  

Microsoft Academic Search

Titania sol–gel layers imprinted with capric acid have been used as synthetic receptors for highly sensitive detection of oxidized products resulting from degradation of automotive engine oil. These layers have been applied as sensitive coating material on shear transverse wave (STW) resonators of frequencies ranging from 100MHz to 430MHz. A relatively small size of STW resonators, i.e. about 2mm for

Adnan Mujahid; Adeel Afzal; Gerd Glanzing; Anton Leidl; Peter A. Lieberzeit; Franz L. Dickert

2010-01-01

270

Preparation of Optical Cores of Silica Optical Fibers by the Sol-Gel Method  

Microsoft Academic Search

Preforms for drawing silica optical fibers have been fabricated by using the MCVD method for the preparation of the optical claddings and the sol-gel method for the preparation of the optical cores consisting of TiO2-SiO2 or RE3+-Al2O3-P2O5-SiO2 (RE = Er, Yb) glasses. A novel method has been developed for depositing thin gel layers on the inner silica tube wall, under

Vlastimil Mat?jec; Miloš Hayer; Marie Pospíšilová; Ivan KaŠík

1997-01-01

271

Synthesis of perovskite electrooptic thin films by polymer modified sol-gel processing.  

E-print Network

??In the present work, Pb0.91La0.09(Zr0.65,Ti0.35)0.9775O3 (PLZT(9/65/35)) and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x=0.23-0.43) perovskite electrooptic (EO) thin films have been synthesized by PVP modified sol-gel processing with lead… (more)

Du, Zehui.

2009-01-01

272

Photocatalytic degradation of pentachlorophenol on TiO 2 sol–gel catalysts  

Microsoft Academic Search

The photocatalytic degradation of pentachlorophenol (PCP) in aqueous solution was investigated using TiO2 catalysts. The samples were prepared by the sol–gel method using different gelation pH and different calcination temperatures. The solids were characterized by specific surface area, X-ray diffraction, UV-Vis absorbance, FTIR and pentachlorophenol adsorption. The catalytic activity of the solids was evaluated in a conventional photoreactor at 298

G. Pecchi; P. Reyes; P. Sanhueza; J. Villaseñor

2001-01-01

273

Room-temperature mirror preparation using sol-gel chemistry and laminar-flow coating technique  

NASA Astrophysics Data System (ADS)

The CEA/DAM megajoule-class pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research is requiring 240 cavity-end mirrors. The mirror design is based on 44-cm square highly-reflective (HR)-coated deformable substrates. Such large dielectric mirrors are using interference quarterwave stacks of SiO2 and ZrO2-PVP (PolyVinylPyrrolidone) thin films starting from sol-gel colloidal suspensions (sols). The colloidal/polymeric ratio of the ZrO2-PVP composite system has been optimized regarding refractive index value, laser damage threshold and chemical interactions have been studied using FT-IR spectroscopy. Therefore a promising deposition technique so- called Laminar Flow Coating (LFC) has been associated to sol-gel chemistry for HR sol-gel coating development. The as-designed LFC prototype machine has been used for coating solution wave deposition by transportation of a tubular dispense unit under the substrate flat surface. Thin film so created by the solvent evaporation was then dried at room temperature or using short wavelength UV-curing built-in station. Optimization of parameters such as optical layer number, coating uniformity, coating edge effect, 1053-nm reflectance and laser damage threshold is discussed. Demonstration has been made that this novel coating method is a competitive way for large-area optical deposition compared to dipping or spinning techniques. Association of sol-gel colloidal suspensions to LFC process appear to be a promising cheap way of producing high power laser optical coatings.

Belleville, Philippe F.; Bonnin, Claude; Lavastre, Eric; Pegon, Philippe; Rorato, Yannick

2001-04-01

274

Preparation of Mullite Fibers by Sol-Gel Process and Study of Their Morphology  

Microsoft Academic Search

Mullite fibers were prepared by sol-gel method using aluminum lactate (AL) and tetraethylorthosilicate (TEOS). The AL was prepared by mixing aluminum nitrate and lactic acid in molar ratio of 1:3. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used to characterize the properties of the gel and ceramic fibers. The gel fibers completely transformed to mullite fibres at

Hongbin Tan; Congsheng Guo; Xiaoling Ma

2011-01-01

275

Study on complex reaction in fabricating ferroelectric ktn ceramics by sol-gel process  

Microsoft Academic Search

In fabricating ferroelectric KTa1 -xNbxO3 (KTN) and KNbO3(KN) ceramics by Sol-Gel process. M2(OC2H5)10 + CH3OH + K(OC2H5 and M2(OC2H5)10 + C2H5OH + K(OC2H5) (M = Nb, Ta) systems have been studied by means of conductometric titration and infrared absorption spectrometry.

A. X. Kuang; E. T. Wu; A. Nazeri-Eshghi; J. D. Mackenzie

1989-01-01

276

Synthesis and properties of KTN films by sol-gel deposition and RF-magnetron sputtering  

Microsoft Academic Search

Homogeneous KTN (Potassium Tantalate Niobate) solutions were prepared using potassium acetate and metal alkoxides in 2-methoxyethanol by controlled hydrolysis with 1:2 (KTN\\/H2O) molar ratio. We report on the synthesis of sol-gel KTN for both the fabrication of homogeneous, dense and stoichiometrically correct ceramic discs by hot isostatic pressing and the deposition of spin-on as well as sputtered thin films. The

BAHADIR TUNABOYLU; SANAT R. SASHITAL; PHIL HARVEY; SADIK C. ESENER; AMAR BHALLA

2001-01-01

277

Optical sensing of high acidity using a sol–gel entrapped indicator  

Microsoft Academic Search

Nuclear fuel reprocessing requires a real-time monitoring of nitric acid concentration in order to optimize extraction yields of valuable uranium and plutonium actinides. Thus, optical fiber sensors using doped sol–gel coatings have been developed to measure HNO3 concentrations in an extensive range 1–10 N. The transmission probes containing the reagent chromoxane cyanine R (CCR) have been tested in pure, plutonium-charged

M. H. Noire; C. Bouzon; L. Couston; J. Gontier; P. Marty; D. Pouyat

1998-01-01

278

Parameters affecting the electrical conductivity of SnO 2 : Sb sol–gel coatings  

Microsoft Academic Search

SnO2:Sb single and multilayer coatings have been prepared by the sol–gel dip and spin coating method, and by spray pyrolysis from various precursor solutions. Subsequently, the films have been heat treated in a convection furnace or by cw CO2 laser irradiation, respectively. The influence of the different deposition and heating techniques on the electrical and morphological properties of the resulting

G Gasparro; J Pütz; D Ganz; M. A Aegerter

1998-01-01

279

Radiation-induced densification of sol–gel SnO 2:Sb films  

Microsoft Academic Search

Thin films of tin oxide doped with antimony (25 at.% nominal) were deposited on either silicon wafers or pyrex plates using the sol–gel dip coating technique. The samples processed on Si consist of a single layer of SnO2:Sb dried at low temperature (150 °C) for 40 min. Three successive layers, subsequently dried and annealed at 500 °C for 1 h,

B. Canut; V. Teodorescu; J. A. Roger; M. G. Blanchin; K. Daoudi; C. Sandu

2002-01-01

280

Micromachined sol–gel carbon nanotube\\/SnO 2 nanocomposite hydrogen sensor  

Microsoft Academic Search

A novel micromachined single wall carbon nanotube (SWCNT) reinforced nanocrystalline tin dioxide gas sensor has been developed. The presence of SWCNT in SnO2 matrix was realized by a spin-on sol–gel process. The SWCNT\\/SnO2 sensor's sensitivity for hydrogen detection has greatly increased by a factor of three, in comparison to that of pure SnO2 sensor. The novel sensor also lowers the

Jianwei Gong; Jianren Sun; Quanfang Chen

2008-01-01

281

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

282

Hybrid glass and sol-gel integrated optical waveguides for absorption-based biosensing  

Microsoft Academic Search

A novel integrated optical planar waveguide platform for absorption-based biosensing is demonstrated. The platform integrates surface ion-exchanged channel waveguides with one-step UV patterned sol-gel structures to define the probing regions. Cytochrome c protein was utilized to characterize the device performance. Spectroscopically specific attenuation of approximately 2 dB in the guided signal occurred at 532nm for 1.4 cm long probing region.

Ismail E. Araci; Nasuhi Yurt; Seppo Honkanen; Sergio B. Mendez; Nasser Peyghambarian

2005-01-01

283

Synthesis of hexagonal barium ferrite nanoparticle by sol-gel method  

Microsoft Academic Search

M-type Ba hexaferrites were successfully synthesized by sol-gel method. Several synthesizing factors, such as pH value, citric acid\\/metal ion ratio, and dispersion agent were mainly discussed. Fine and pure powders of BaFe12O19 were optimally synthesized under the conditions of the pH value is 7 and citric acid\\/metal ion ratio is 3. The X-ray diffraction analysis demonstrates that no impurity is

Limin DONG; Zhidong HAN; Yaoming ZHANG; Ze WU; Xianyou ZHANG

2006-01-01

284

Structural transformation with milling on sol-gel precursor for BaM hexaferrite  

Microsoft Academic Search

The structural modification upon milling in an intermediate step precursor of the sol-gel method for BaFe12O19 hexaferrite BaM production is discussed. The milling of the precursor diminishes the powder particle size, leads to a more homogeneous matrix and induces a solid-state transformation, from gamma-Fe2O3 to alpha-Fe2O3. The induced modifications of the precursors change the magnetic and structural properties of the

E. Estevez Rams; R. Martinez Garcia; E. Reguera; H. Montiel Sanchez; H. Y. Madeira

2000-01-01

285

Magnetic Properties of Nanocrystalline Barium Hexaferrite Thin Films Prepared by Sol-Gel Method  

Microsoft Academic Search

Single-phase nanocrystalline BaFe12O19 thin films have been prepared on Si (110) substrates by sol-gel method. The efforts have been done to reduce the crystallite size of the single-phase barium hexaferrite thin films in order to develop the thin films for high-density magnetic recording media. Precursor solutions were primed with various Fe\\/Ba ratios and two kinds of basic agents. Then the

S. Salemizadeh; S. A. Seyyed Ebrahimi

2009-01-01

286

Nanostructural control of the release of macromolecules from silica sol–gels  

PubMed Central

The therapeutic use of biological molecules such as growth factors and monoclonal antibodies is challenging in view of their limited half-life in vivo. This has elicited the interest in delivery materials that can protect these molecules until released over extended periods of time. Although previous studies have shown controlled release of biologically functional BMP-2 and TGF-? from silica sol–gels, more versatile release conditions are desirable. This study focuses on the relationship between room temperature processed silica sol–gel synthesis conditions and the nanopore size and size distribution of the sol–gels. Furthermore, the effect on release of large molecules with a size up to 70 kDa is determined. Dextran, a hydrophilic polysaccharide, was selected as a large model molecule at molecular sizes of 10, 40 and 70 kDa, as it enabled us to determine a size effect uniquely without possible confounding chemical effects arising from the various molecules used. Previously, acid catalysis was performed at a pH value of 1.8 below the isoelectric point of silica. Herein the silica synthesis was pursued using acid catalysis at either pH 1.8 or 3.05 first, followed by catalysis at higher values by adding base. This results in a mesoporous structure with an abundance of pores around 3.5 nm. The data show that all molecular sizes can be released in a controlled manner. The data also reveal a unique in vivo approach to enable release of large biological molecules: the use more labile sol–gel structures by acid catalyzing above the pH value of the isoelectric point of silica; upon immersion in a physiological fluid the pores expand to reach an average size of 3.5 nm, thereby facilitating molecular out-diffusion. PMID:23643607

Radin, Shula; Bhattacharyya, Sanjib; Ducheyne, Paul

2013-01-01

287

Development of nanograined hexagonal barium ferrite thin films by sol–gel technique  

Microsoft Academic Search

Nanograined hexagonal barium ferrite (BaFe12O19) thin films have been developed on naturally oxidized Si substrates by sol–gel technique using aqueous solution of metal chlorides. Coated films were heat treated at different temperatures ranging from 450 to 900 °C, and all the films were characterized by using X-ray diffraction (XRD), inductive coupled plasma (ICP) spectroscopy, and field emission scanning electron microscopy

Nimai Chand Pramanik; Tatsuo Fujii; Makoto Nakanishi; Jun Takada

2005-01-01

288

Electrical switching in sol-gel-derived SiO2 films  

Microsoft Academic Search

We have investigated electrical switching behavior of sol-gel derived SiO2 films in c-Si(p)\\/SiO2\\/metal structures. The SiO2 film is fabricated from silicafilm (a soluble Si polymer in dissolved in denatured alcohol) using spin-coating technique. The thickness of the film is in the range of 300~2000 Å which depends on both spinning speed and the degree of dilution. We find that, with

Jian Hu; Scott Ward; Qi Wang

2003-01-01

289

New Synthesis of Ferrite–Silica Nanocomposites by a Sol–Gel Auto-Combustion  

Microsoft Academic Search

A sol–gel autocombustion method was used to synthesize nanometric metal-oxide powders, and was extended for the first time to prepare ferrite–silica nanocomposites. The gels obtained by mixing suitable amounts of citric acid, metal nitrates, ammonia (pure phases) and tetraethylortosilicate (nanocomposites) were converted directly to ferrite (either ?-Fe2O3 or CoFe2O4) or ferrite–silica composites through a rapid autocombustion reaction. The combustion involves

C. Cannas; A. Musinu; D. Peddis; G. Piccaluga

2004-01-01

290

Preparation of LiMn 2O 4 thin films by a sol–gel method  

Microsoft Academic Search

LiMn2O4 thin films were prepared by a sol–gel method using spin-coating and annealing processes. Anhydrous Mn(CH3COCHCOCH3)3 (manganese acetylacetonate) and LiCH3COCHCO–CH3 (lithium acetylacetonate) were chosen as source materials. The film electrochemical properties depended on the drying temperature even when subjected to the same annealing conditions. The discharge capacity of annealed film increased as the drying temperature was increased. However, the rate

Y. J Park; J. G Kim; M. K Kim; H. T Chung; H. G Kim

2000-01-01

291

CHARACTERIZATION OF CERIUM-DOPED YTTRIUM ALUMINIUM GARNET NANOPOWDERS SYNTHESIZED VIA SOL-GEL PROCESS  

Microsoft Academic Search

In this work the sol-gel process was used to prepare Ce-doped yttrium aluminium garnet (Y3Al5O12, YAG) samples. The synthesis products were characterized by infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD), and transmission electron microscopy (TEM). The particle size and luminescence properties of synthesized samples were also determined. The XRD patterns of Y3Al5O12:Ce samples showed that phase purity of garnets

A. Katelnikovas; T. Jüstel; D. Uhlich; J.-E. Jørgensen; S. Sakirzanovas; A. Kareiva

2008-01-01

292

Structure and dielectric properties of sol–gel 9\\/65\\/35 PLZT thin films  

Microsoft Academic Search

Ferroelectric lead lanthanum zirconate titanate thin films were prepared by a sol–gel method on Pt(111)\\/TiO2\\/SiO2\\/Si substrate. The texture selection was observed to be very sensitive to the preparation routine and samples with different preferred orientation were produced. The large- or fine-grained microstructure was observed depending on film thickness. The dielectric measurements of 360nm thick film performed in the frequency window

A. Khodorov; M. Pereira; M. J. M. Gomes

2005-01-01

293

Zinc oxide films prepared by sol-gel spin-coating  

Microsoft Academic Search

The d.c. electrical conductivity and optical properties of undoped zinc oxide films prepared by the sol-gel process using a spin-coating technique were investigated. The ZnO films were obtained by 10 cycle spin-coated and dried zinc acetate films followed by annealing in air at 500–575°C. The films deposited on the Pyrex glass substrate were polycrystalline and c-axis oriented. A minimum film

Y. Natsume; H Sakata

2000-01-01

294

Fluor-hydroxyapatite sol–gel coating on titanium substrate for hard tissue implants  

Microsoft Academic Search

Hydroxyapatite (HA) and fluor-hydroxyapatite (FHA) films were deposited on a titanium substrate using a sol–gel technique. Different concentrations of F? were incorporated into the apatite structure during the sol preparation. Typical apatite structures were obtained for all coatings after dipping and subsequent heat treatment at 500°C. The films obtained were uniform and dense, with a thickness of ?5?m. The dissolution

Hae-Won Kim; Hyoun-Ee Kim; Jonathan C. Knowles

2004-01-01

295

In situ ion-beam analysis and modification of sol-gel zirconia thin films  

SciTech Connect

We report the investigation of ion-beam-induced densification of sol-gel zirconia thin films via in situ ion backscattering spectrometry. We have irradiated three regions of a sample with neon, argon, and krypton ions. For each ion species, a series of irradiation and analysis steps were performed using an interconnected 3 MV tandem accelerator. The technique offers the advantages of minimizing the variation of experimental parameters and sequentially monitoring the densification phenomenon with increasing ion dose.

Levine, T.E. [Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering; Yu, Ning; Kodali, P.; Walter, K.C.; Nastasi, M.; Tesmer, J.R.; Maggiore, C.J. [Los Alamos National Lab., NM (United States); Mayer, J.W. [Arizona State Univ., Tempe, AZ (United States). Dept. of Chemical, Bio and Materials Science Engineering

1995-05-01

296

Sol-gel synthesis of nanostructured materials based on aluminum oxide with preset texture properties  

Microsoft Academic Search

Different mesoporous nanoarchitectures of aluminum oxide are obtained by heat treatment of the products of a sol-gel process\\u000a involving an ultrasonic treatment and using polyethylene amine, dodecyl sulfate, and dodecylamine as templates. The structure\\u000a of the materials has been studied by the methods of low-temperature adsorption of nitrogen and diffraction of X-rays at small\\u000a and large Bragg angles. Depending on

V. V. Vinogradov; A. V. Agafonov; A. V. Vinogradov

2010-01-01

297

Al coordination in sol–gel and conventional calcium aluminate glasses  

Microsoft Academic Search

We present the results of a study in which we compared one aspect of structure for a conventionally prepared glass and sol–gel material in the calcium aluminate (CA) family, of composition 50CaO·50Al2O3 (wt%). The work was directed towards a comparison of the aluminum coordination in the two materials, which was determined via 27Al magic angle spinning nuclear magnetic resonance (MAS

Lori Kerns; Michael C Weinberg; Sharon Myers; Roger Assink

1998-01-01

298

Sol-gel synthesis of hybrid organic-inorganic materials. Hexylene and phenylene-bridged polysiloxanes  

Microsoft Academic Search

New highly cross-linked polysiloxanes were prepared by sol-gel polymerization of 1,6-bis(diethoxymethylsilyl)hexane (1) and 1,4-bis(diethoxymethylsilyl)benzene (2). Hydrolysis and condensation of 1 and 2 under acidic and basic conditions with 4 equiv of water led to the rapid formation of hexylene- and phenylene-bridged polysiloxane gels. The dry gels (xerogels) were intractable, insoluble materials that were noticeably hydrophobic, exhibiting no swelling in organic

Douglas A. Loy; Gregory M. Jamison; Brigitta M. Baugher; Sharon A. Myers; Roger A. Assink; Kenneth J. Shea

1996-01-01

299

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

Microsoft Academic Search

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

Satyajit Vishnu Shukla

2002-01-01

300

Sol-Gel Synthesis and Phase Evolution Behavior of Sterically Stabilized Nanocrystalline Zirconia  

Microsoft Academic Search

Nanocrystalline as well as submicron sized, non-agglomerated, spherical ZrO2 particles have been successfully synthesized using the sol-gel technique utilizing hydroxypropyl cellulose (HPC) as a polymeric steric stabilizer. The effect of various parameters such as the ratio of molar concentration of water and alkoxide (R), the molar concentration (HPC) and the molecular weight (MWHPC) of HPC polymer as well as the

S. SHUKLA; S. SEAL; R. VANFLEET

2003-01-01

301

Sol-Gel Synthesis and Phase Evolution Behavior of Sterically Stabilized Nanocrystalline Zirconia  

Microsoft Academic Search

Nanocrystalline as well as submicron sized, non-agglomerated, spherical ZrO2 particles have been successfully synthesized using the sol-gel technique utilizing hydroxypropyl cellulose (HPC) as a polymeric steric stabilizer. The effect of various parameters such as the ratio of molar concentration of water and alkoxide (R), the molar concentration [HPC] and the molecular weight (MWHPC) of HPC polymer as well as the

S. Shukla; S. Seal; R. Vanfleet

2003-01-01

302

Synthesis and Characterization of LiMVO4 Cathode Material Produced by Sol-gel Method  

NASA Astrophysics Data System (ADS)

Lithium manganese vanadate (LiMnVO4) has been prepared by a sol-gel method. XRD analysis reveals that the prepared sample possess orthorhombic structure. Laser Raman spectrum shows the local environment of cations vibrational modes with respect to neighboring oxygen atom. The ionic conductivity of the sample is found to be 8.5×10-5 S cm-1 at 350 °C.

Prakash, D.; Jayachandran, M.; Sanjeeviraja, C.

2011-07-01

303

Effects of sol–gel processing parameters on the phases and microstructures of HA films  

Microsoft Academic Search

Bioactive hydroxyapatite (HA) films were fabricated by a sol–gel method and triethylphosphate and calcium nitrate were used as the phosphorus and calcium precursors, respectively. The effects of the heat treatment temperature, pH level and substrate materials on the phases and microstructures of HA films were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic probe microanalysis (EPMA) and

Diangang Wang; Chuanzhong Chen; Xiuna Liu; Tingquan Lei

2007-01-01

304

A 29Si NMR study of the sol-gel polymerisation rates of substituted ethoxysilanes  

Microsoft Academic Search

29Si nuclear magnetic resonance spectroscopy has been used to generate reaction profiles for the acid-catalysed hydrolysis and condensation of various substituted ethoxysilanes which may be used in sol-gel processes. Experiments were performed at acid concentrations that enabled hydrolysis rate determinations to be made both with and without the influence of the condensation process. The relative rates of both hydrolysis and

Robert J. Hook

1996-01-01

305

A new sol–gel process for producing Na 2O-containing bioactive glass ceramics  

Microsoft Academic Search

The sol–gel process of producing SiO2–CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na2O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However,

Qi-Zhi Chen; Yuan Li; Li-Yu Jin; Julian M. W. Quinn; Paul A. Komesaroff

2010-01-01

306

Investigation on bio-mineralization of melt and sol–gel derived bioactive glasses  

Microsoft Academic Search

The bio-mineralization properties of the melt-derived bioactive glass 45S5 and the sol–gel derived bioactive glasses 58S and 77S were investigated and compared using in vitro test combined with BET, XRD, FTIR and SEM techniques. It was found that the surfaces of the three bioactive glasses could be mineralized by immersion in a simulated body fluid (SBF) at 37°C for several

Xiaofeng Chen; Yongchun Meng; Yuli Li; Naru Zhao

2008-01-01

307

Adsorption equilibrium and kinetics of fluoride on sol–gel-derived activated alumina adsorbents  

Microsoft Academic Search

Adsorption equilibrium and kinetics of fluoride on a sol–gel-derived activated alumina and its modifications with calcium oxide or manganese oxide were studied to explore the feasibility of applying these adsorbents for fluoride removal from drinking water. The activated alumina adsorbents were characterized with SEM\\/EDS and N2-adsorption for their chemical and pore textural properties. The adsorption isotherms were correlated with the

Lucy M. Camacho; Arely Torres; Dipendu Saha; Shuguang Deng

2010-01-01

308

Chitosan-based tyrosinase optical phenol biosensor employing hybrid nafion\\/sol–gel silicate for MBTH immobilization  

Microsoft Academic Search

The development of an optical biosensor based on immobilization of 3-methyl-2-benzothiazolinone hydrazone (MBTH) in hybrid nafion\\/sol–gel silicate film and tyrosinase in chitosan film for the detection of phenolic compounds has been described. Tyrosinase was immobilized in chitosan film deposited on the hybrid nafion\\/sol–gel silicate film containing MBTH. The enzymatic oxidation product of phenolic compounds were stabilized through formation of adduct

Jaafar Abdullah; Musa Ahmad; Lee Yook Heng; Nadarajah Karuppiah; Hamidah Sidek

2006-01-01

309

A one-dimensional analysis of sol-gel film-coating drying: Pore evolution, network shrinkage and stress development  

Microsoft Academic Search

Highly porous sol-gel films have potential applications as electrical and thermal insulators, catalyst supports, sensors, and membranes for gas separations. Pore dimensions in these sol-gel films are usually small e.g., on the order of tens of nanometers or less. Their successful fabrications, however, greatly depend on the fundamental understanding of mechanisms that underlie the phenomena of pore evolution, network shrinkage,

K. S. Chen; P. R. Schunk

1998-01-01

310

Phase transformation of nanostructured titanium dioxide from anatase-to-rutile via combined ultrasound assisted sol–gel technique  

Microsoft Academic Search

An effort was made to synthesize nanostructured TiO2 via sol–gel technique to obtain a 100% rutile polymorph of nanostructured TiO2. The sol–gel synthesis technique was suitably modified by incorporating ultrasound to study the effect of cavitation on the phase transformation, crystallite size, crystallinity and morphological (scanning electron microscopy) properties of the obtained nano-TiO2. It was observed that using ultrasound, yield

Krishnamurthy Prasad; D. V. Pinjari; A. B. Pandit; S. T. Mhaske

2010-01-01

311

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

312

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

313

A sintering study of novel sol--gel-based nanocluster catalysts  

SciTech Connect

The authors introduce two novel synthesis strategies to make nanoclusters on silica and alumina supports using inverse micelle technology and sol-gel processing. In the first method, sol-gel chemistry (hydrolysis and condensation of metal alkoxides) is performed in alcohol-free inverse micelle, metal cluster solutions. In the second method, metal clusters formed in traditional inverse micelle solutions are allowed to diffuse into preexisting wet monoliths formed using traditional sol-gel techniques. The different materials produced are characterized and compared with respect to particle size and the substrate properties using N{sub 2} porosimetry methods, chemisorption, atomic absorption, and transmission electron microscopy. The effect of calcination on particle and support stability is determined and discussed in terms of the metal coverage and the relationship between particle size and pore dimensions. The authors conclude that the relative sizes of particles and pores has no clear effect on sintering behavior. Sintering appears to be predominantly dependent on metal loading normalized against the support surface area suggesting Ostwald ripening as the sintering mechanism.

Martino, A.; Sault, A.G.; Kawola, J.S.; Boespflug, E.; Phillips, M.L.F.

1999-10-01

314

A study on the effect factors of sol-gel synthesis of yttrium aluminum garnet nanopowders  

NASA Astrophysics Data System (ADS)

Yttrium aluminum garnet (YAG) nanopowders were synthesized by sol-gel method using aluminum nitrate, yttrium nitrate, and citric acid as starting materials, de-ionized water, ethanol, and ethylene glycol as solvents, respectively. The phase formation process, state of particle size distribution (PSD), compositions, morphological characteristics, and thermal behavior of the powders were investigated by means of x-ray diffractometry, PSD, Fourier transform infrared, transmission electronic microscope, and thermogravimetry-differential scanning calorimetry. Results indicate that the formation and characteristics of precursor gel and YAG powder, such as the rate of gelation, average particle size, and powder agglomerate state, strongly depend on the stoichiometric amount of citric acid, the solvent composition, and the precalcination process. Highly crystalline, well-dispersed YAG nanopowder was obtained by calcining at 800 °C for 2 h in the presence of citric acid to nitrate ratio of 3, ethanol solvent, and precalcination process. According to the analysis of experimental results, sol-gel chemistry, DLVO theory, and steric effect, the effects of stoichiometric amount of citric acid, solvent composition, and precalcination process on the formation and characteristics of precursor gel and YAG powder have been discussed. Meanwhile, the overall synthesis mechanism in sol-gel method has been suggested.

Yang, Lin; Lu, Tiecheng; Xu, Hui; Zhang, Wei; Ma, Benyuan

2010-03-01

315

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

2015-01-21

316

Organic Thin Film Transistors with Gate Dielectrics via Sol-Gel Process  

NASA Astrophysics Data System (ADS)

The presents work focuses on the preparation of gate dielectrics by the sol-gel process and the characterization of resultant organic thin film transistor (OTFTs). The basic requirements for the gate dielectric materials of OTFTs are high dielectric constant, low leakage current and the patternability. To obtain suitable gate dielectrics, the feasibility of sol-gel process and UV crosslinking were investigated. Acryl UV resin (DCS-SP210, Dongjin Semichem Co.,Ltd.), titanium n-butoxide, HCl and acetyl acetone were used to prepare a hybrid reaction medium. We obtained the result that the leakage current of dielectric layer was maintained under 10-9 A in the OTFTs operating voltage, the dielectric constant was about 9 at 10 KHz and the rms was about 2-3 nm. OTFTs were fabricated with pentacene (45 nm) and the resultant dielectric layer. The field effect mobility and on-off ratio were 1.1 cm^2/V-s and 10^4, respectively. The result proved that sol-gel hybrid system was suitable for the gate dielectrics of OTFTs in the requirements of the electric, dielectric property and the patternability.

Choi, June Whan; Choi, Sungwon; Yu, Jae-Woong; Yoon, Ho Gyu; Kim, Jai-Kyeong

2007-03-01

317

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

318

Fabrication of superhydrophobic sol-gel composite films using hydrophobically modified colloidal zinc hydroxide.  

PubMed

A superhydrophobic sol-gel composite film was fabricated by incorporating hydrophobically modified colloidal zinc hydroxide (CZH) in sol-gel matrix. CZH was prepared by controlled precipitation and modified by treatment with stearic acid. The concentration of stearic acid and stirring time were optimized to obtain modified CZH with very high water contact angle (WCA) of 165 degrees and sliding angle (SA)<2 degrees . X-ray diffraction (XRD) analysis has shown that the crystal structure of CZH was mainly composed of epsilon-zinc hydroxide and the modified CZH indicated the presence of zinc stearate. The modified CZH film exhibited a microstructure which resembled clusters of interconnected rods creating roughness on the film surface. The modified CZH suspension was dispersed in an acid-catalyzed sol of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) and spray-coated on glass slides to prepare sol-gel composite coatings. The concentration of CZH in the composite film was optimized to obtain superhydrophobic surfaces. FTIR spectrum also confirmed the presence of zinc stearate in the composite film. The method is simple and cost-effective and does not involve any expensive chemicals or equipments. PMID:19720382

Lakshmi, R V; Basu, Bharathibai J

2009-11-15

319

Fluorimetric detection of boron by azomethine-H in micellar solution and sol-gel  

NASA Astrophysics Data System (ADS)

Mixtures of boron and azomethine-H in solution result in slow complexation. Addition of sodium dodecyl sulfate (SDS), polyethylene glycol dodecyl ether (Brij-35), 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TritonX-100), and cetyltrimethyl ammonium bromide (CTAB) result in considerable decrease in complexation time and enhancement in signal of peak in solution and also sol-gel. The fluorescence of the complex is monitored at an emission wavelength of 486 nm with excitation at 416 nm. The presence of 1 × 10 -3 mol L -1 SDS decreased the complexation time up to 10 min in solution and 20 min in sol-gel for above 0.25 ?g B mL -1 and 30 min in solution and 35 min in sol-gel for below 0.25 ?g B mL -1. However, the photostability did not change by adding micelle in both media. The proposed method shows a linear response toward boron in the concentration range of 0.05-10 ?g mL -1 and is selective for boron over a large number of electrolytes and cations. The detection limit was 7 ?g L -1. This method has been used for the detection of boron in environmental water samples and fruit juices with satisfactory results.

Merdivan, Erinc; Benibol, Yalim; Seyhan, Serap

2009-01-01

320

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

321

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

322

PREPARATION AND CHARACTERISATION OF A SOL-GEL PROCESS ?-AL2O3 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

2014-05-01

323

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

324

Synthesis and Electrical Properties of ?-Na x Co2O4 via a Citrate Sol-Gel Method with Polyethylene Glycol 400  

NASA Astrophysics Data System (ADS)

In this work, a citrate sol-gel method (Sol-Gel) with polyethylene glycol 400 (Sol-Gel-PEG400) was developed to prepare ?-Na x Co2O4 by using sodium and cobalt nitrates as the raw materials, citric acid as a complexing agent, and PEG400 as a dispersant. At 800°C, single-phase ?-Na x Co2O4 crystals were obtained using Sol-Gel-PEG400. With the addition of 1 vol.% PEG400, smaller, flaky particles exhibited a well-tiled structure along the plane direction of the flaky particles. Moreover, polycrystalline sintered bulk ?-Na x Co2O4 with more highly oriented crystals and greater compact density was fabricated using the Sol-Gel-PEG400 synthesized powders compared with the powders synthesized by citrate Sol-Gel. The electrical conductivity ( ?) values of Sol-Gel-PEG400 samples were higher than those of Sol-Gel samples between 400 K and 900 K. The ? value of Sol-Gel-PEG400 increased to 3.13 × 104 Sm-1 at 400 K and to 1.84 × 104 Sm-1 at 900 K. Between 400 K and 850 K, the Seebeck coefficient ( ?) values of Sol-Gel-PEG400 samples were slightly lower than those of Sol-Gel samples. Near 900 K, the ? values of these two methods were nearly equal, at 164 ?V K-1. Between 400 K and 900 K, the power factor ( P) of Sol-Gel-PEG400 was evidently larger than that of Sol-Gel.

Zhang, Li; Tang, Xinfeng; Gao, Wenbin

2010-09-01

325

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

326

Rational design of Ag/TiO2 nanosystems by a combined RF-sputtering/sol-gel approach.  

PubMed

The present work is devoted to the preparation of Ag/TiO(2) nanosystems by an original synthetic strategy, based on the radio-frequency (RF) sputtering of silver particles on titania-based xerogels prepared by the sol-gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF-sputtering, whose combination enables the obtainment of a tailored dispersion of Ag-containing particles into the titania matrix. In addition, the system's chemico-physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 degrees C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), secondary ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron diffraction (ED), high-angle annular dark field scanning TEM (HAADF-STEM), energy-filtered TEM (EF-TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo-dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties. PMID:19882618

Armelao, Lidia; Barreca, Davide; Bottaro, Gregorio; Gasparotto, Alberto; Maccato, Chiara; Tondello, Eugenio; Lebedev, Oleg I; Turner, Stuart; Van Tendeloo, Gustaaf; Sada, Cinzia; Stangar, Urska Lavrencic

2009-12-21

327

Thermally stable supported metal catalysts and inorganic membranes prepared by sol-gel processing  

NASA Astrophysics Data System (ADS)

The application of sol-gel processing to the synthesis of supported metal catalysts, inorganic membranes and catalytic membranes was studied. Noble metals were supported on SiO2 and gamma-Al2O 3. These materials have high surface areas, well-defined pore size distributions, and average pore diameters around 4 nm. The effects of preparative variables such as pH, gelation temperature, metal precursor, metal loading and binder addition on the final properties of the materials were studied. The structure of the sol-gel derived support materials was used to stabilize the dispersion of the supported metal at elevated temperatures and enhance activity and selectivity of the catalyst. The thermal stability of a sol-gel Rh/SiO2 catalyst was tested at 650°C in flowing O2 and compared to the stability of a similar sample prepared by the traditional method of ion-exchange. The ion-exchanged sample had an average pore diameter of 24 nm. The metal particle size distribution of the sol-gel catalyst was more stable due to the smaller pore diameter of that catalyst. The sol-gel samples were more active in the dehydrogenation of n-butane than the ion-exchanged sample. A similar effect of pore size was found for Pd/gamma-Al2O3 catalysts sintered in H 2 at 650°C. The Pd/gamma-Al2O3 catalysts were found to be very active hydrogenation catalysts but were not selective to partially hydrogenated products. A boehmite sol was used as a coating on a porous alpha-Al 2O3 substrate to form a gamma-Al2O3 membrane that could act as a diffusion barrier for gases. A catalytic membrane was formed by adding a soluble palladium compound to the sol. The Pd/gamma-Al 2O3 membrane was used successfully in the selective hydrogenation reactions of acetylene and 1,3-butadiene to produce ethylene and butenes. This was accomplished by premixing the alkyne or diene with H2 and passing it through the membrane wall, therefore reducing the contact time between the reactants and the catalyst.

Lambert, Christine Kay

1998-12-01

328

Optical properties of distributed feedback waveguide lasers based on sol-gel glass  

NASA Astrophysics Data System (ADS)

Distributed feedback (DFB) waveguide laser based on sol-gel materials have generated much interest because of the versatility of sol-gel technique and the potential applications in integrated optics. In this dissertation, Optical properties of sol-gel waveguides based on zirconia materials with or without dye dopants have been investigated by spectroscopic ellipsometry (SE) in the wavelength range from 300 to 800 nm. Lasing characteristics of asymmetric and symmetric DFB waveguide lasers have also been studied. Zirconia, zirconia-ORMOSIL and zirconia-titania-ORMOSIL films on silicon and glass substrates were prepared by sol-gel method with the thickness from 0.1 to 10 mum. The dispersion curves rose sharply at shorter wavelengths, as expected of typical shape of a dispersion curve near an electronic interband transition. By varying ORMOSIL ratio and the annealed temperature from room temperature to 500°C, the refractive indices changed from 1.53 to 2.15. The extinction coefficients was in the range from 1 x 10-4 to 1 x 10-3. Furthermore, some degree of inhomogeneity has been found in zirconia films when they were treated at the temperature over 200°C. The addition of ORMOSIL and titania improved the microstructure of the zirconia films, and made possible films as thick as 10 mum. The complex refractive index of zirconia films doped with rhodamine 6G, rhodamine 640 and oxazine 725 was deduced from SE spectra using classical Lorentz model. The derived absorption spectra agreed well with those measured by spectrophotometer. Unlike the pure zirconia films, the spectra of refractive index for dye-doped films exhibited anomalous dispersion. Moreover, the SE spectra of the layered waveguide structures were analyzed by appropriate models. For the multilayer structure, the volume fraction of titania-silica in the interlayer was found to decrease with the initial thickness of the guiding films. Highly homogeneous sol-gel zirconia and zirconia-ORMOSIL films doped with rhodamine 6G, rhodamine 640 and oxazine 725 on glass substrates have been used in a distributed feedback configuration to obtain tunable laser emission from yellow to near infrared region. As many as eight pairs of TE/TM waves corresponding to eight propagation modes were simultaneously produced by circularly polarized crossing beams in a R6G-doped zirconia-titania-ORMOSIL waveguide laser of 6.7 mum thickness. Symmetric waveguide laser with guiding film of 0.1 mum was also achieved by using a cover layer of sol-gel titania-silica whose refractive index matches that of the glass substrate. Furthermore, the photostability of the R6G and R640 in different sol-gel hosts were investigated. Compared with titania-silica, zirconia-ORMOSIL and zirconia-titania-ORMOSIL, zirconia seemed ideal as a host matrix for functional organic dopants in view of stable lasing emission and high photostability.

Shi, Lei

329

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

330

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

331

Sol-gel Er-doped SiO2-HfO2 planar waveguides: A viable system for 1.5 mum application  

NASA Astrophysics Data System (ADS)

70SiO2-30HfO2 planar waveguides, doped with Er3+ concentrations ranging from 0.3 to 1 mol %, were prepared by sol-gel route, using dip-coating deposition on silica glass substrates. The waveguides show high densification degree, effective intermingling of the two components of the film, and uniform surface morphology. Propagation losses of about 1 dB/cm were measured at 632.8 nm. When pumped with 987 or 514.5 nm continuous-wave laser light, the waveguides show the 4I13/2[right arrow]4I15/2 emission band with a bandwidth of 48 nm. The spectral features are found independent both on erbium content and excitation wavelength. The 4I13/2 level decay curves presented a single-exponential profile, with a lifetime between 2.9 and 5.0 ms, depending on the erbium concentration.

Goncalves, R. R.; Carturan, G.; Zampedri, L.; Ferrari, M.; Montagna, M.; Chiasera, A.; Righini, G. C.; Pelli, S.; Ribeiro, S. J. L.; Messaddeq, Y.

2002-07-01

332

Eu3+ probe ion for rare-earth dopant site structure in sol-gel derived LiYF4 oxyfluoride glass-ceramic  

NASA Astrophysics Data System (ADS)

Sol-gel route using metal alkoxides and trifluoroacetic acid as precursors has been used to prepare oxyfluoride glass-ceramic containing Eu3+-doped LiYF4 nanocrystals of about tens of nm size embedded in a silica matrix through controlled crystallization at higher temperatures of the xerogel. Photoluminescence spectra and decay curves recorded in the Eu3+-doped LiYF4 polycrystalline pellet and glass ceramic have been discussed using group-theoretical arguments. In the glass-ceramic Eu3+ ions are embedded dominantly inside the LiYF4 nanocrystals most probably as Eu-O center and/or dimer centers in low symmetry (C2v) sites; oxygen ions were incorporated in their neighborhood during the glass ceramization.

Secu, C. E.; Negrea, R. F.; Secu, M.

2013-10-01

333

Evolution of Structural, Optical and Electrical Characteristics of Spin-Coated CdO Thin Films with the Gelation State of the Sol-Gel  

NASA Astrophysics Data System (ADS)

The present work is intended to investigate the influence of the gelation state of the sol-gel on the properties of spin-coated cadmium oxide (CdO) thin films. The viscosity of the sol-gel increases at a slow uniform rate up to 5 days (break-off point) after which the rise becomes progressively more rapid and it attains saturation after 10 days of gelation. Films have been grown with gelation times of 2 days, 4 days, 6 days, 8 days, 9 days and 10 days. The visual characteristics of the films have been discussed in terms of the centrifugal force acting on the sol-gel. The sol-gel viscosity seems to be better suited to represent the gelation state of the sol-gel rather than the gelation time. The x-ray diffraction studies show that lower gelation times and lower sol-gel viscosities give rise to single crystalline CdO thin films while gelation times of 6 days and above (i.e. sol-gel viscosities of 2.92 × 10-3 N s m-2 and more) yield polycrystalline CdO thin films. The gelation state of the sol-gel has been found to have a strong bearing on the properties of CdO thin films, and highly conducting and transparent CdO thin films can be achieved by controlling the gelation state of the sol-gel and the results obtained have been reported.

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

2014-09-01

334

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

335

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

336

Thermal Infrared Reflective Metal Oxide Sol-Gel Coatings for Carbon Fiber Reinforced Composite Structures  

NASA Astrophysics Data System (ADS)

Recent trends in composite research include the development of structural materials with multiple functionalities. In new studies, novel materials are being designed, developed, modified, and implemented into composite designs. Typically, an increase in functionality requires additional material phases within one system. The presence of excessive phases can result in deterioration of individual or overall properties. True multi-functional materials must maintain all properties at or above the minimum operating limit. In this project, samples of antimony and cobalt-doped tin oxide (ATO(Co2O 3)) sol-gel solutions are used to coat carbon fibers and are heat treated at a temperature range of 200 - 500 °C. Results from this research are used to model the implementation of sol-gel coatings into carbon fiber reinforced multifunctional composite systems. This research presents a novel thermo-responsive sol-gel/ (dopant) combination and evaluation of the actuating responses (reflectivity and surface heat dissipation) due to various heat treatment temperatures. While ATO is a well-known transparent conductive material, the implementation of ATO on carbon fibers for infrared thermal reflectivity has not been examined. These coatings serve as actuators capable of reflecting thermal infrared radiation in the near infrared wavelengths of 0.7-1.2 ?m. By altering the level of Co2O3 and heat treatment temperatures, optimal optical properties are obtained. While scanning electron microscopy (SEM) is used for imaging, electron diffraction spectroscopy (EDS) is used to verify the compounds present in the coatings. Fourier transform infrared (FT-IR) spectroscopy was performed to analyze the chemical bonds and reflectivity in the infrared spectra after the heat treatments. Total reflection and angle-dependent reflectivity measurements were performed on the coatings in the wavelengths of 0.7-2 ?m. Laser induced damage threshold testing was done to investigate the dielectric breakdown and used to calculate surface temperatures.

Richard, Brandon Demar

337

Structural Characterization and Corrosion Behavior of Stainless Steel Coated With Sol-Gel Titania  

NASA Astrophysics Data System (ADS)

Sol-gel titania films were prepared from hydrolysis and condensation of titanium (IV) isopropoxide. Diethanolamine was used as chelant agent in titania synthesis. 316L stainless steel substrates were dip-coated at three different withdrawal speeds (6, 30, and 60 mm/min) and heated up to 400 °C. Thermogravimetry and differential thermal analyses of the titania gel solution evinced a continuous mass loss for temperatures up to 800 °C. The transition of anatase to the rutile phase begins at 610-650 °C, being the rutile transformation completed at 900 °C. The thicknesses of the films were determined as a function of the heat treatment and withdrawal speed. It was observed that their thicknesses varied from 130 to 770 nm. Scanning electron microscopy images of the composites revealed the glass-like microstructure of the films. The obtained sol-gel films were also characterized by energy dispersive spectroscopy. The chemical evolution of the films as a function of the heating temperature was evaluated by Fourier transform infrared spectroscopy (specular reflectance method). After performing the adhesion tests, the adherence of the titania films to the stainless steel substrate was excellent, rated 5B according to ASTM 3359. The hardness of the ceramic films obtained was measured by the Knoop microindentation hardness test with a 10 g load. We observed that the titania film became harder than the steel substrate when it was heated above 400 °C. The corrosion rates of the titania/steel composites, determined from potentiodynamic curves, were two orders of magnitude lower than that of the bare stainless steel. The presence of the sol-gel titania film contributed to the increase of the corrosion potential in ca. 650 mV and the passivation potential in ca. 720 mV.

Vasconcelos, Daniela C. L.; Nunes, Eduardo H. M.; Sabioni, Antônio Claret S.; da Costa, João C. Diniz; Vasconcelos, Wander L.

2012-03-01

338

An innovative CaSiO 3 dielectric material from eggshells by sol–gel process  

Microsoft Academic Search

Calcium silicate (CaSiO3), wollastonite, with a molar ratio of CaO:SiO2 of 1:1, was synthesized by a sol–gel process and sintered at 1,100°C for 1 h. The synthesis of calcium silicate was carried\\u000a out using chicken eggshells as the starting material possessing several advantages such as low cost, high purity, and less\\u000a moisture sensitivity, when compared with those obtained from metal alkoxide

Nuchnapa Tangboriboon; Tunchanoke Khongnakhon; Supawinee Kittikul; Ruksapong Kunanuruksapong; Anuvat Sirivat

2011-01-01

339

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

340

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

PubMed

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. PMID:23892122

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

2013-11-01

341

Preparation of optical cores of silica optical fibers by the sol-gel method  

Microsoft Academic Search

Preforms for drawing silica optical fibers have been fabricated by using the MCVD method for the preparation of the optical\\u000a claddings and the sol-gel method for the preparation of the optical cores consisting of TiO2?SiO2 or RE3+?Al2O3?P2O5?SiO2 (RE=Er, Yb) glasses. A novel method has been developed for depositing thin gel layers on the inner silica tube wall, under\\u000a rotation of

Vlastimil Matêjec; Milo? Hayer; Marie Pospí?ilová; Ivan Ka?ík

1997-01-01

342

YAG:Ce3+ Nanophosphor Synthesized with the Salted Sol-Gel Method  

SciTech Connect

Nano-phosphors of Y3Al5O12:Ce3+ (YAG:Ce) were synthesized with a novel salted sol-gel method, in which aqueous solution of inorganic salts (yttrium/cerium nitrates) were used along with the metal alkoxide precursor, aluminum sec-butoxide, Al(OC4H9)3. YAG single phase was formed at temperature as low as 800 ?C. Luminescence of YAG:Ce reached the maximum intensity when calcined above 1350C. The SEM image reveals that the grain sizes of the nano-phosphors calcined at 1100 ?C are in a range of 50-150 nm.

D. Jia; C. V. Shaffer; J. E. Weyant; A. Goonewardene; X. Guo; Y. Wang; X. Z. Guo; K. K. Li; Y. K. Zou; W. Jia

2006-05-01

343

Spectroscopic investigation of the photochemistry of uranyl-doped sol-gel glasses immersed in ethanol  

SciTech Connect

Uranyl ion (UO{sub 2}{sup 2+}) has been doped in silica glasses through a sol-gel process. The photochemistry of UO{sub 2}{sup 2+}-doped glasses immersed in ethanol solution has been investigated. Our experimental results indicate that UO{sub 2}{sup 2+} in this system can be photochemically converted to U(IV) species, and evidence is provided for the possible formation of U(IV) species via a subsequent chemical reduction of the intermediate UO{sub 2}{sup +} instead of the conventional bimolecular disproportionation reaction. The latter mechanism is known to be a dominant mechanism for the photochemical reactions in homogeneous solutions.

Dai, Sheng; Metcalf, D.H.; Del Cul, G.D.; Toth, K.M. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States)

1996-12-18

344

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

345

Fabrication of silica glass containing yellow oxynitride phosphor by the sol-gel process  

NASA Astrophysics Data System (ADS)

We have prepared silica glass by the sol-gel method and studied its ability to disperse the Ca-?-SiAlON:Eu2+ phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON.

Segawa, Hiroyo; Yoshimizu, Hisato; Hirosaki, Naoto; Inoue, Satoru

2011-06-01

346

Magnetic properties of Co-doped ZnO prepared by sol–gel method  

Microsoft Academic Search

Zn1?xCoxO (0sol–gel method. The structure and magnetism analysis indicate that Co2+ ions substitute for Zn2+ ions to form a solid solution with wurtzite structure of ZnO. Zn1?xCoxO (0.03?x?0.09) are paramagnetic at 300K, but ferromagnetic component seems to exists in the Zn1?xCoxO (x=0.01 and 0.02). Low-temperature (about 150K) ferromagnetism is found in Zn1?xCoxO (0

J. H. Yang; L. Y. Zhao; X. Ding; L. L. Yang; Y. J. Zhang; Y. X. Wang; H. L. Liu

2009-01-01

347

Preparation and characterisation of apatite-type lanthanum silicates by a sol-gel process  

Microsoft Academic Search

Recent reports have indicated good fast oxide ion conductivity in apatite silicates. In this article we report on the successful low temperature synthesis of the apatite-type lanthanum silicates, La10(SiO4)6O3 and La9.33(SiO4)6O2, via a sol-gel process. The properties of the resulting apatite phases have been characterised by thermal analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and conductivity measured by

Shanwen Tao; John T. S Irvine

2001-01-01

348

Structural transformation with milling on sol-gel precursor for BaM hexaferrite  

NASA Astrophysics Data System (ADS)

The structural modification upon milling in an intermediate step precursor of the sol-gel method for BaFe12O19 hexaferrite BaM production is discussed. The milling of the precursor diminishes the powder particle size, leads to a more homogeneous matrix and induces a solid-state transformation, from ?-Fe2O3 to ?-Fe2O3. The induced modifications of the precursors change the magnetic and structural properties of the final BaM hexaferrite compared to the BaM obtained from the non-milled precursor.

Estevez Rams, E.; Martinez Garcia, R.; Reguera, E.; Montiel Sanchez, H.; Madeira, H. Y.

2000-11-01

349

Preparation of barium ferrite films with high Fe\\/Ba ratio by sol–gel method  

Microsoft Academic Search

Hexagonal BaFe12O19 ferrite (BaM) thin films were prepared on Si (100) substrate successfully by sol–gel technology and post annealing. The results\\u000a showed the BaM phase can be formed and crystallized into c-axis textured grains even when the Fe\\/Ba ratio of the precursor\\u000a varied from 6.5 to 9.5. However, the behavior of the saturation magnetization (M\\u000a s) and intrinsic coercivity (H

Hui Li; Jie Huang; Qingfeng Li; Xiaodong Su

2009-01-01

350

Sol-gel synthesis of normal spinel LiMn 2 O 4 and its characteristics  

Microsoft Academic Search

Normal spinel LiMn2O4 was synthesized by sol-gel method using lithium nitrate, manganese nitrate, citric acid and ethylene glycol as raw materials.\\u000a LiMn2O4 was characterized by XRD, TG-DTA, IR, SEM and AAS. The optimum conditions for the synthesis were explored. Citric acid and\\u000a ethylene glycol were mixed with molar ratio of 0.25, and the mixture was esterified at 140°C for 4

Lei Jia-heng; Sun Yu-bin; Chen Yong-xi; Wang Jin-rong; Xue Li-hui

2002-01-01

351

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

352

Synthesis and Conductometric Property of Sol-Gel-Derived ZnO/PVP Nano Hybrid Films  

NASA Astrophysics Data System (ADS)

ZnO nanoparticles immobilized in polyvinylpyrrolidone (PVP) were prepared using sol-gel dip-coating technique with varying Zn2+/PVP ratios. The films were characterized using atomic force microscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy for chemical analysis. The size and concentration of ZnO particles decreased as the Zn/PVP ratio decreased. Under low Zn2+/PVP molar ratios, ZnO particles were clearly well separated and capped in the PVP polymer matrix. Electrical resistivity of 108 ? cm was achieved under these deposition conditions.

Ilegbusi, Olusegun J.; Trakhtenberg, Leonid

2013-03-01

353

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

SciTech Connect

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, E-mail: mickael.gilliot@univ-reims.fr; Hadjadj, Aomar [LISM, Université de Reims Champagne-Ardenne, Reims (France); Eypert, Céline [HORIBA Jobin Yvon S.A.S., Palaiseau (France)

2013-11-14

354

Tunable Bragg stacks from sol-gel derived Ta2O5 and MEL zeolite films  

NASA Astrophysics Data System (ADS)

In this paper we investigated sol-gel derived Ta2O5 and nanosized MEL zeolite films obtained by spin coating of Tantalum sol and colloidal zeolite solution, respectively. Refractive index and thickness of the films were determined using non-linear curve fitting of measured reflectance spectra. The influence of the post deposition annealing on the optical properties and thickness of the films was studied. Besides tunable Bragg stacks were designed and prepared by layer-by-layer deposition of Ta2O5 and MEL suspensions with quarter-wave thicknesses. The influence of water, acetone and methanol on the optical behavior of Bragg stacks was discussed.

Gospodinov, B.; Dikova, J.; Mintova, S.; Babeva, T.

2012-12-01

355

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

356

Sol-gel nanocrystalline ZnO:Ag films: Structural and optical properties  

NASA Astrophysics Data System (ADS)

The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The films are obtained by spin coating method on quartz and Si substrates. The effect of the annealing temperatures (500-800 °C) and the gas ambient (oxygen and nitrogen) has been studied by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). Optical properties are investigated by UV-VIS spectroscopy. The transmittance spectra of ZnO:Ag films are differed from ZnO spectra and manifest absorption features due to silver nanoparticles formation.

Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

2014-06-01

357

Photo-induced birefringence in DR1-doped sol-gel silica and ORMOSILs thin films  

NASA Astrophysics Data System (ADS)

Photo-induced birefringence has been measured by a pump-probe experiment in pure silica and ORMOSILs (ORganically MOdified SILanes) thin films containing Disperse Red 1 (DR1). The films are obtained via the sol-gel process using TEOS, GLYMO and ICPTEOS as precursors. Two characteristic relaxation times have been estimated for the relaxation of the birefringence: a short time, related to the Cis ? Trans isomerization of the dye molecule, which does not depend on the hosting matrix, and a longer time, due to the angular diffusion towards the isotropy, strongly sensitive to the chemical bonding of the DR1 molecule with the host.

Marino, I. G.; Bersani, D.; Lottici, P. P.

2000-12-01

358

Holographic gratings in DR1-doped sol-gel silica and ORMOSILs thin films  

NASA Astrophysics Data System (ADS)

Holographic diffraction gratings have been obtained in Disperse Red 1 (DR1)-doped silica and ORganically MOdified SILanes thin films (ORMOSILs), produced by tetraethylorthosilicate (TEOS) and 3-(triethoxysilyl)propyl isocyanate (ICPTEOS) as precursors for the sol-gel process. For the DR1 + TEOS film, the grating is associated to an irreversible bleaching of the dye and may be detected by a Raman micro-spectroscopy mapping. For films based on ICPTEOS, a transient phase diffraction grating is created by the photoinduced birefringence. Two characteristic relaxation times of the birefringence grating have been measured.

Marino, I. G.; Bersani, D.; Lottici, P. P.

2001-01-01

359

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

360

The effect of solid particles addition in sol-gel processing of ceramic matrix composites  

NASA Astrophysics Data System (ADS)

The addition of solid particles to the sol-gel processing of ceramic matrix composites increases composite green density and reduces cracking caused by drying stresses. 3D angle interlock woven carbon fiber preforms were infiltrated with silica sol containing colloidal silica with selected particle sizes. A pressure infiltration apparatus was used to fabricate composites. Higher composite green densities were obtained with smaller particle sizes. The addition of a deflocculant to the sol increased interparticle repulsive forces, thus enhancing particle packing and composite green density. Particle coating to prevent flocculation also increased composite green density.

Liu, Hsien-Kuang; Parvizi-Majidi, Azar

1992-10-01

361

Influence of POST Annealing on Sol-Gel Deposited ZnO Thin Films  

NASA Astrophysics Data System (ADS)

The effect of annealing temperature on sol-gel deposited ZnO thin films have been studied. The average crystallite size determined from XRD shows that the deposited films are nanocrystalline. FTIR confirms deposition of ZnO thin films. The transmittance of annealed ZnO thin films is greater than 80% in visible region with bandgap ranging from 3.25-3.19 eV. The films annealed at 450°C temperature shows lower resistivity value of 527.241 ?m. The deposited nanocrystalline films are suitable for biosensing applications due to its higher surface area.

Bhadane, Hemalata; Samuel, Edmund; Gautam, Dinesh Kumar

2014-05-01

362

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

363

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

364

Investigation on bio-mineralization of melt and sol gel derived bioactive glasses  

NASA Astrophysics Data System (ADS)

The bio-mineralization properties of the melt-derived bioactive glass 45S5 and the sol-gel derived bioactive glasses 58S and 77S were investigated and compared using in vitro test combined with BET, XRD, FTIR and SEM techniques. It was found that the surfaces of the three bioactive glasses could be mineralized by immersion in a simulated body fluid (SBF) at 37 °C for several hours. The bio-mineralized products on the surfaces of the bioactive glasses were apatite microcrystals with a low crystallinity, but the composition and morphologies of the apatite microcrystals on three glasses were different.

Chen, Xiaofeng; Meng, Yongchun; Li, Yuli; Zhao, Naru

2008-11-01

365

Fabrication of inverted zinc oxide photonic crystal using sol–gel solution by spin coating method  

PubMed Central

Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the sol–gel solution of ZnO by spin-coating method. It is easily able to control and fabricate the photonic crystal structures using the self-organized PSS with a size of 193 nm. The inverted ZnO photonic crystal structures observed show the (111) tendency of the hexagonal compact arrangement formation. The resulting structures possess the photonic band gaps in the near-ultraviolet range and exhibit an enhanced photoluminescence spectrum. The technology can effectively increase the light output intensity or efficiency for the applications of optoelectronic devices. PMID:23819709

2013-01-01

366

Barium hydroxyapatite nanoparticles synthesized by citric acid sol-gel combustion method  

SciTech Connect

Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant at a relatively low temperature of 600 deg. C. The thermal decomposition of nitrate-citrate xerogel was investigated by thermogravimetric/differential thermal analysis (TG/DTA) technique. The yielding powders calcined at 600 deg. C have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The possible combustion process was presented.

Xiu Zhiliang [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Lue Mengkai [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)]. E-mail: mklu@icm.sdu.edu.cn; Liu Suwen [Department of Material Science and Engineering, Shandong Institute of Light Industry, Jinan 250100 (China); Zhou Guangjun [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Shandong Supervision and Inspection Institute for Product Quality, Jinan 250100 (China); Su Benyu [Shandong Supervision and Inspection Institute for Product Quality, Jinan 250100 (China); Zhang Haiping [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

2005-09-01

367

Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method  

SciTech Connect

The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

2004-01-03

368

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

369

Combined removal of SO2 and NO using sol-gel-derived copper oxide coated alumina sorbents/catalysts.  

PubMed

The present paper reports experimental results on the removal of sulfur dioxide and nitrogen oxide from simulated flue gas using a copper oxide coated on alumina sorbent/catalyst prepared by the sol-gel method. Selective catalytic reduction of nitric oxide by ammonia over sol-gel derived CuO/gamma-Al2O3 sorbents/catalysts with different degrees of sulfation was studied in a fixed-bed packed reactor. The optimum temperature for NO reduction was found at 350 degrees C for both fresh and sulfated catalysts. The properties for simultaneous removal of SO2 and NO by the sol-gel-derived CuO/gamma-Al2O3 sorbents were studied using simulated dry flue gas. The optimum operating temperature for the combined deSO2/deNO operations was identified at 350 degrees C. At the space velocity of 5200 h(-1) and 350 degrees C, a fixed-bed reactor packed with the 7.9 wt% CuO/gamma-Al2O3 sorbent prepared by the sol-gel method offers SO2 sorption capacity of 2.3 mmol g(-1) and NO conversion of 92% with a dry simulated flue gas as the feed. Under these experimental conditions, the sol-gel derived sorbents/catalysts have comparable efficiency for removal of SO2 and NOx as their commercial counterparts. The significantly higher crush strength of the sol-gel derived sorbents/catalysts make them very promising for their use in the copper oxide process for combined removal of SO2 and NOx from flue gas in a single unit operation. PMID:14599142

Buelna, G; Lin, Y S

2003-09-01

370

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; Maria, Carmelo De; Montemurro, Francesca; Chauhan, Veeren M; Aylott, Jonathan W; Vozzi, Giovanni

2015-01-01

371

Sol-gel method to fabricate CaP scaffolds by robocasting for tissue engineering.  

PubMed

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol-gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and ?-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2-12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 ?m in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol-gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances. PMID:22311079

Houmard, Manuel; Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P

2012-04-01

372

Lead magnesium niobate-lead titanate fibres by a modified sol-gel method  

SciTech Connect

Lead magnesium niobate-lead titanate (PMN-PT) ceramic fibres with the nominal composition of 0.65Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.35PbTiO{sub 3} have been fabricated by a modified sol-gel method. Due to the difficulty of dissolving the magnesium component, the mixed oxide method was used together with the traditional sol-gel method. To obtain crack-free fibres, pyrolysis was carried out at a very slow heating rate under specific atmosphere to control the organic burnout. The thermal and microstructural properties were investigated using thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. The optimum sintering temperature is 1200 deg. C and yields a fibre with a final diameter of around 100 {mu}m. A single PMN-PT fibre has been poled and its electrical properties were measured. The properties of the fibre are found to be better than that of a ceramic disc.

Lam, K.-H. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong (China)]. E-mail: 02900857r@polyu.edu.hk; Li Kun [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong (China); Chan, H.L.-W. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong (China)

2005-11-03

373

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

374

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

375

Encapsulated metal nanocluster materials prepared by a novel inverse micelle/sol-gel technique  

SciTech Connect

A wide variety of manometer sized metal and semiconductor particles (Au, Ag, Pd, Pt, Rh, Fe, Ni, CdS, MoS{sub 2} and FeS{sub 2}) can be prepared using an inverse micelle technique. Such materials are of great interest for their potential use in catalytic, photochemical, electrochemical and optical applications but their practicality is often hindered by the agglomeration of the particles. Agglomeration may be prevented by using a porous support matrix where the nanoclusters are sterically trapped within the pores. The sol-gel process results in the formation of such a porous support material. We have thus combined the technique of forming metal nanoclusters in inverse micelle solutions with the technique of forming sol-gel materials. Using our novel method, we have succeeded in preparing manometer sized metal colloids encapsulated in both xerogel and aerogel materials. Characterization of these materials has been carried out by TEM, SEM, UV/Vis, NMR and nitrogen sorption porosimetry.

Yamanaka, S.A.; Martino, A.; Kawola, J.S. [Sandia National Labs., Albuquerque, NM (United States)] [and others

1995-12-31

376

Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method  

PubMed Central

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with xAg = 0.5 are effective against E. coli and S. aureus after 24?h. PMID:24523630

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

377

Oxide and organic nano-porous sol-gel materials synthesized for lipid bilayer formation  

NASA Astrophysics Data System (ADS)

Sol-gel synthesized materials have many applications and in this thesis, different sol-gel films have been investigated as a scaffolding substrate for vesicle-fused lipid bilayers. Oxide, organic, and phosphate-based xerogels have been characterized using methods such as scanning electron microscopy (SEM), x-ray diffraction (XRD), atomic force micrsocopy (AFM) and contact angle goniometry to determine their viability as lipid membrane supports. Membranes containing 1,2-Dioleoyl-Glycero-3-Phosphocholine (DOPC) and two-phase lipid bilayer membranes containing DOPC and 1,2-Distearoyl-Glycero-3-Phosphocholine (DSPC) have been successfully assembled on these surfaces and characterized using fluorescence microscopy and fluorescence recovery after photobleaching (FRAP) to determine the lateral mobility and diffusion coefficients of these unique systems. It was found that xerogel films with rough surface topography lead to slower lipid diffusion due to obstruction of the membrane. Further work is needed to determine if more complexities, which are found in real cell membranes, can be accommodated by these new substrate chemistries. Additionally, sugar-based aerogel and xerogel materials were synthesized for catalytic applications. These unique materials were characterized with SEM and BET surface area and pore size analysis and it was found that sucrose aerogels, with high surface area and smaller pore diameters, are the most promising sugar-based material studied for further catalysis research.

Nellis, Barbara

378

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

379

“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

380

Thermal behavior of ZrO 2 precursors obtained by sol-gel processing  

NASA Astrophysics Data System (ADS)

Three different zirconia precursors were synthesized from zirconium(IV)-propoxide by sol-gel processing at pH 1.5, 5.5 and 10.5. The first crystallization products, obtained after the calcination of ZrO 2 precursors at 400°C, contained metastable t-ZrO 2 as a dominant phase. The sensitivities of metastable t-ZrO 2 products to the influence of temperature (600°Cand 800°C) or pressure (500, 1000 and 1350 MPa) were monitored by laser Raman and FT-IR spectroscopies. X-ray powder diffraction was used as a complementary technique. It was found that the pH, used during the sol-gel processing of the ZrO 2 precursor strongly influenced the sensitivity of the metastable t-ZrO 2 products to the influence of temperature or pressure. The most stable t-ZrO 2 product was obtained from the ZrO 2 precursor precipitated at pH 1.5 and the most susceptible from the precursor precipitated at pH 5.5.

Štefan?, I. I.; Musi?, S.; Štefani?, G.; Gajovi?, A.

1999-05-01

381

Chitosan-PEG Hydrogel with Sol-Gel Transition Triggerable by Multiple External Stimuli.  

PubMed

Smart hydrogels play an increasingly important role in biomedical applications, since materials that are both biocompatible and multi-stimuli-responsive are highly desirable. A simple, organic solvent-free method is presented to synthesize a biocompatible hydrogel that undergoes a sol-gel transition in response to multiple stimuli. Methoxy-poly(ethylene glycol) (mPEG) is modified into carboxylic-acid-terminated-methoxy-poly(ethylene glycol) (mPEG-acid), which is then grafted onto chitosan via amide linkages yielding mPEG-g-chitosan. Grafting of mPEG onto hydrophobic chitosan imparts hydrophilic properties to the resultant polymer. The mPEG-g-chitosan gel exhibits a controllable multi-stimuli-responsive property. The balance between hydrophilicity and hydrophobicity is believed to confer mPEG-g-chitosan with stimuli-responsive behavior. The effect of salt concentration, solute concentration, temperature, and pH on the sol-gel transition of mPEG-g-chitosan is evaluated and the underlying mechanisms of mPEG-g-chitosan polymer packing and gelation property is discussed. PMID:25522283

Tsao, Ching Ting; Hsiao, Meng Hsuan; Zhang, Mengying Y; Levengood, Sheeny Lan; Zhang, Miqin

2015-02-01

382

Sol-gel MnO 2 as an electrode material for electrochemical capacitors  

NASA Astrophysics Data System (ADS)

MnO 2 was synthesized by the sol-gel method. Two forms of MnO 2, namely xerogel and ambigel, were prepared by reduction of NaMnO 4 and KMnO 4 with sodium fumarate. The synthesized products were characterized using X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and chemical analysis. Electrochemical characterization was carried out using cyclic voltammetry by a three electrode system consisting of saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and sol-gel prepared MnO 2 mounted on Ti mesh used as working electrode. Aqueous NaCl, KCl, Na 2SO 4 and LiCl solutions were used as electrolytes. The ambigel form of MnO 2 showed high capacitance compared to that of the xerogel form of MnO 2. Maximum capacitance of 130 F/g was obtained at a scan rate of 5 mV/s for the ambigel form of MnO 2 in a 2 M NaCl solution. Effect of NaCl concentration on the capacitance of MnO 2 was studied. Stability of MnO 2 was studied up to 800 cycles.

Reddy, Ravinder N.; Reddy, Ramana G.

383

Dialkylenecarbonate-Bridged Polysilsesquioxanes. Hybrid Organic Sol-Gels with a Thermally Labile Bridging Group  

SciTech Connect

In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, volubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300-350 C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.

Loy, D.A.; Beach, J.V.; Baugher, B.M.; Assink, R.A.; Shea, K.J.; Tran, J.; Small, J.H.

1999-04-21

384

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

385

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

386

Application of sol-gel techniques to thin-film superconductor systems  

NASA Astrophysics Data System (ADS)

This paper discusses the preparation and characterization of sol-gel produced thin films for barrier layer and high Tc superconductor applications. Hydrolyzed metal alkoxide solutions were spin coated on Si substrates with subsequent thermal processing. Barrier layers of alkaline earth oxides, perovskites, Y2O3, ZrO2 and others were produced. Characterization was performed via SEM, XRD, ESCA, Auger depth profiling and four point probe resistivity measurements for 1-2-3 thin films. On Si wafers, barrier layer films were fairly smooth with some cracking and pitting present. Si migration was severe for alkaline earth thin films on Si wafers. Some perovskite films on Si showed formation of Ba-Si-O phases at the Si interface. Thin films of 1-2-3 on sol-gel produced barrier layers of SrTiO3 or ZrO2 on Si showed Ba pileup at the Si interface and were not superconducting. 1-2-3 layers deposited on single crystal ZrO2 were superconducting and showed onset temperatures of 90 K with zero resistance reached at about 55 K. SEM morphology differences were observed for the different 1-2-3 preparations.

Wandass, J. H.; Cambria, F. M.; Whitwell, G. E.

1990-01-01

387

Evaporation induced self assembly and rheology change during sol-gel coating  

NASA Astrophysics Data System (ADS)

Thin films with self-assembled nanostructures are important in applications such as catalysis and biosensor technology. A major technique used to prepare such films is sol-gel processing. This technique involves depositing a complex fluid on a substrate by dip, spin, or spray coating, followed by allowing the film to evaporate and form self-assembled nanostructures. Since the composition of the film during coating is central to understanding how changing chemical and physical conditions affect the properties and microstructures of the films, we investigate the rheological properties of the entrained fluid film and its subsequent impact on the steady state film thickness during the evaporation-induced self-assembly process. We perform systematic experiments to measure the meniscus shape and film thickness during sol-gel dip coating. We observe that the experimental data of film thickness lie way below the Landau-Levich-Derjaguin prediction from the classic film-coating results. To explain this discrepancy, we present a thin film model based on the lubrication approximation with an evaporation effect. Our results show that evaporation-induced self-assembly leads to rheological variations in the entrained film and, consequently, alters the film thickness. The predicted film thickness based on the evaporation-induced rheology variation model compares well with the experiments.

Lee, Chang H.; Lu, Yunfeng; Shen, Amy Q.

2006-05-01

388

Sol gel derived hydroxyapatite coatings on titanium and its alloy Ti6Al4V  

NASA Astrophysics Data System (ADS)

Titanium has been used for many medical and dental applications; however, its joining to a living bone is not satisfactorily good or the implant integration with bone tissue takes several months.The aim of this work is to produce hydroxyapatite (HAP) coatings on titanium and its alloy for facilitating and shortening the processes towards osseointegration. HAP coatings were obtained by sol-gel method with sol solutions prepared from calcium nitrate tetrahydrate and triammonium phosphate trihydrate as the calcium and phosphorous sources. Two types of gelatine were added to the sol: agar-agar or animals gelatine. Both were found to enhance the formation and stability of amorphous HAP using soluble salts as the sources of calcium and phosphate. HAP coatings were deposited from HAP-GEL sol using dip-withdrawal technique, then the plates were dried and annealed at temperatures 460-750 °C. FTIR spectroscopy and XRD analysis were used to study the phase composition of phosphate coatings. Morphology and chemical analysis of HAP layers was performed using a scanning electron microscope equipped with an energy dispersive X-ray analyser (SEM+EDX). The biological activity of sol-gel phosphate coatings was observed during thermostatic held in simulated body fluid (SBF). It was found that chemical composition and structure of HAP coatings depends on pH and final thermal treatment of the layer.

Stoch, A.; Jastrzebski, W.; D?ugo?, E.; Lejda, W.; Trybalska, B.; Stoch, G. J.; Adamczyk, A.

2005-06-01

389

Sol–gel method to fabricate CaP scaffolds by robocasting for tissue engineering  

PubMed Central

Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol–gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and ?-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2–12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 ?m in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol–gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances. PMID:22311079

Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

2012-01-01

390

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

391

Sol-gel auto-combustion synthesis of zinc ferrite for moderate temperature desulfurization  

SciTech Connect

Zinc ferrite as a desulfurization sorbent with an average crystallite size of about 36 nm was synthesized by a sol-gel auto-combustion method. The precursor for the sorbent was a gel obtained from metal nitrates and citric acid by a sol process. The nitrate-citrate gel exhibits a self-propagating combustion behavior, and after combustion, it can transform into a nanosized spinel structured zinc ferrite directly. The prepared sorbent has a larger specific surface area and higher reactivity when compared with the sorbent achieved by a solid mixing method, and it could efficiently reduce the H{sub 2}S concentration from 6000 ppm to less than 2 ppm at a moderate temperature range. The sulfur capacity at 400{sup o}C reaches about 38.5 g of sulfur/100 g of sorbent, which corresponds to 96.4% of the theoretical value. The temperature programmed oxidation test for the sulfided sorbent shows that the most sulfur is desorbed before 500{sup o}C. XRD results confirm that the sulfided sample after exposure to a 5% O{sub 2}/N{sub 2} gas mixture at 500{sup o}C can be regenerated completely, which indicates that the regeneration temperature of the sorbent prepared by the sol-gel auto-combustion method could be greatly reduced. 40 refs., 10 figs., 2 tabs.

Rongjun Zhang; Jiejie Huang; Jiantao Zhao; Zhiqiang Sun; Yang Wang [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry

2007-09-15

392

Sol-gel derived ZnO thin films: Effect of amino-additives  

NASA Astrophysics Data System (ADS)

Zinc oxide thin films were dip-coated from an alcoholic sol of zinc acetate with different amino-additives including monoethanolamine, diethanolamine, triethanolamine, triethylamine, and ethylenediamine. Sol-gel behavior, crystal structure, optoelectronic and morphological properties of thin films were investigated with focus on the effects of different amines and drying conditions. Investigations explicate the role of chemical and physical properties of amines such as organic chains, polarity, and boiling point as the main factors that cause distinct sol-gel behavior and film properties. It is shown that different amines in different molar ratios together with drying temperature cause dramatic impacts on sol transparency, stability, and consequently on structural, optoelectronic, and morphological properties of films. Notably, monoethanolamine and triethylamine films demonstrate a preferred orientation stimulated by increased molar ratio of amines. Further investigations indicated the positive effect of elevated drying temperature particularly on those films prepared from sols with high-boiling-point stabilizers. The variation of film optoelectronics seems to depend mainly on heat treatment, whereas sol chemistry influences the optical properties indirectly through the structural alteration. Peculiar morphologies in the ethylenediamine films disappeared with adjusting the drying conditions. The size of ZnO grains were approximately independent of amine types and primarily affected by the heat treatment

Hosseini Vajargah, P.; Abdizadeh, H.; Ebrahimifard, R.; Golobostanfard, M. R.

2013-11-01

393

Effect of the photosensitizer on the photorefractive effect using a low T g sol-gel glass  

Microsoft Academic Search

We prepared the photorefractive sol-gel glass based on organic-inorganic hybrid materials containing a charge transporting\\u000a molecule, second-order nonlinear optical (NLO) chromophore, photosensitizer, and plasticizer. Carbazole and 2-{4-[(2-hydroxy-ethyl)-methyl-amino]-benzylidene}-malononitrile\\u000a were reacted with isocyanatotriethoxy silane and the functionalized silanes were employed to fabricate the efficient photorefractive\\u000a media including 2,4,7-trinitrofluorenone (TNF) to form a charge transfer complex. The prepared sol-gel glass samples showed\\u000a a

Dong Hoon Choi; Woong Gi Jun; Kwang Yong Oh; Han Na Yoon; Jae Hong Kim

2003-01-01

394

Crystal structure and luminescent properties of nanocrystalline YAG and YAG:Nd synthesized by sol-gel method  

NASA Astrophysics Data System (ADS)

The work describes results of synthesis of undoped and Nd-doped YAG nanopowders by sol-gel method using different complexing agents (ethylene glycol and citric acid) and characterization of the material by X-ray powder diffraction, scanning electron microscopy, photoluminescence and thermoluminescence techniques. Utilization of citrate sol-gel procedure using yttrium and aluminum nitrate nonahydrates as starting substances allowed to obtain highly stoichiometric and non-defected YAG and YAG:Nd nanocrystalline samples with good luminescence performance and low radiation storage efficiency.

Zhydachevskii, Ya.; Syvorotka, I. I.; Vasylechko, L.; Sugak, D.; Borshchyshyn, I. D.; Luchechko, A. P.; Vakhula, Ya. I.; Ubizskii, S. B.; Vakiv, M. M.; Suchocki, A.

2012-10-01

395

Comparison of the Sol-gel Method with the Coprecipitation Technique for Preparation of Hexagonal Barium Ferrite  

Microsoft Academic Search

Hexagonal barium ferrite BaFe12O19 particles were prepared by sol-gel and coprecipitation methods, respectively. The composition of the so-obtained materials was investigated by means of XRD. By the sol-gel method, non-anticipated intermediate crystalline phases, such as ?-Fe2O3, ?-Fe2O3, BaCO3, and BaFe2O4etc., were formed with the delay of the formation of BaFe12O19. The formation of single phase BaFe12O19 required calcination at 850

Jing-ping WANG; Ying LIU; Mi-lin ZHANG; Ying-jie QIAO; Tian XIA

2008-01-01

396

An electrochemical investigation of Li intercalation in the sol-gel LiMn 2O 4 spinel oxide  

Microsoft Academic Search

An alternative approach for obtaining the LiMn2O4 spinel phase is provided by the use of the sol-gel method in aqueous solution. The main electrochemical properties of the sol-gel LiMn2O4 phase are reported. In addition to chronopotentiometric and voltammetric experiments, the kinetics of the electrochemical insertion–extraction of lithium in LixMn2O4 (0.25

S Bach; J Farcy; J. P Pereira-Ramos

1998-01-01

397

Evanescent wave absorption based fiber optic pH sensor prepared by dye doped sol-gel immobilization technique  

NASA Astrophysics Data System (ADS)

A fiber optic pH sensor based on evanescent wave absorption is presented. To prepare the probe a small length of the cladding is removed from the middle portion of the fiber. A thin porous film of glass with pH-sensitive dye entrapped in it is deposited on the surface of the unclad portion of the fiber using sol-gel technology. The sensor response and its dynamic range are reported for phenol red, cresol red and bromophenol blue dyes. The sol-gel process has been found to increase the dynamic range of the pH sensor.

Gupta, B. D.; Sharma, D. K.

1997-02-01

398

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 select solvents that produced porous xerogels from two different polyurethane sol-gel formulations. The process effectively combines a set of methods that search the sol-gel formulation spaces for both shape-memory and porosity. Easily produced dense xerogels from trial sol-gel formulations are sufficient for DSC and initial DMA shape-memory test data, as well as standard solvent swelling and extraction test data to support the search for shape memory and the computation of rankings to select solvent(s) that is most likely to produce a porous xerogel. Accelerated degradation tests on the dense xerogels also produced results useful to guide further testing of the sol-gel formulations. Standard shape-memory research testing only characterizes the free return to shape or the shape memory force with no return from a tensile test. Characterization of the scaffold's compressive shape memory (percent strain recovery under stress) offers a clinical user design data for interactions with body tissue. Standard tensile shape memory ratios were translated to the compressive stress, strain, and temperature cycles used to characterize the shape-memory abilities of the two sol-gel families tested. The advantage of a thermoset polymer's ability to achieve 100% shape memory repeatability is demonstrated. This scaffold's compressive shape memory actuation energy density was above 6.0 KJ/m 3 over a range of recovery strains from 5% to 12%.

Lippincott, Hugh Walker

399

Efficiently Reflected Ultrasound on Production of Sol-Gel TiO2 Powder: Properties and Photodegradation to Rhodamine 640  

NASA Astrophysics Data System (ADS)

In 45 kHz ultrasound (US), sol-gel derived anatase-TiO2 powder was prepared using a stainless steel reflection plate. We found that reflected US reduced the particle size of TiO2 thereby increasing the reactive surface area for photodegradation to Rhodamine 640 (Rh-640). We found that the reflected US focused high sound intensity onto a part of the sol-gel reaction. When the surface area of TiO2 powder, which was prepared using reflected US, was increased, photodegradation to Rh-640 was enhanced.

Latt, Kyaing Kyaing; Kobayashi, Takaomi

2007-05-01

400

Soft-lithography-enabled fabrication of large numerical aperture refractive microlens array in hybrid SiO2-TiO2 sol-gel glass  

NASA Astrophysics Data System (ADS)

This paper describes a low-cost soft-lithography method for building large-numerical-aperture microlenses in hybrid sol-gel glass. The fabrication processes comprise three steps, namely fabrication of large numerical aperture microlens array in photoresist as a master, replication of the master in poly-dimethylsiloxane (PDMS) as elastomeric molds and reproduction of the PDMS replica onto the hybrid sol-gel glass as an end structure. Comparing with the direct UV fabrication in the photosensitive sol-gel glass, the proposed method provides a unique advantage in terms of fabrication freedom in shape and thickness of micro-optical elements in the sol-gel glass. This eliminates the difficulties in direct photolithography in sol-gel glass for arbitrary shapes and great thickness due to ever increasing demands.

Yuan, X.-C.; Yu, W. X.; He, M.; Bu, J.; Cheong, W. C.; Niu, H. B.; Peng, X.

2005-03-01

401

High surface area neodymium phosphate nano particles by modified aqueous sol-gel method  

SciTech Connect

Graphical abstract: Synthesis of nano rod shaped neodymium phosphate particles with specific surface area as high as 107 m{sup 2} g{sup -1} and particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m. Highlights: Black-Right-Pointing-Pointer Nano size neodymium phosphate is synthesized and characterized using a novel modified aqueous sol gel process. Black-Right-Pointing-Pointer Specific surface area above 100 m{sup 2} g{sup -1} achieved without the addition of any complexing agents. Black-Right-Pointing-Pointer High sintered density reported than the density obtained for powder synthesized through conventional solid state reaction. Black-Right-Pointing-Pointer The particles are nano sized and have rod shape morphology and are retained at higher temperatures. Black-Right-Pointing-Pointer An average grain size of {approx}1 {mu}m obtained for sintered NdPO{sub 4} after thermal etching at 1400 Degree-Sign C. -- Abstract: Synthesis of nano rod shaped neodymium phosphate (NdPO{sub 4}) particles with specific surface area as high as 107 m{sup 2}g{sup -1} and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 Degree-Sign C. NdPO{sub 4} was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m.

Sankar, Sasidharan [Materials Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695 019, Kerala (India)] [Materials Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695 019, Kerala (India); Warrier, Krishna Gopakumar, E-mail: wwarrierkgk@yahoo.co.in [Materials Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695 019, Kerala (India); Komban, Rajesh [Institut fuer Chemie, Anorganische Chemie 1, Universitaet Osnabrueck, Barbarastrasse 7, 49069 Osnabrueck (Germany)] [Institut fuer Chemie, Anorganische Chemie 1, Universitaet Osnabrueck, Barbarastrasse 7, 49069 Osnabrueck (Germany)

2011-12-15

402

Encapsulation of fluorescence vegetable extracts within a templated sol-gel matrix  

NASA Astrophysics Data System (ADS)

The sol-gel encapsulation of labile substances with specific properties and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Numerous studies have been reported in the field of sol-gel processes regarding different physical and chemical packing of sensitive biomolecules encapsulated in silica matrix. In this paper the classical sol-gel synthesis has been used under mild conditions in order to minimize denaturizing effects on encapsulated active vegetable extracts from flavones class. The silica templated matrix was obtained by using two types of surfactants with different alkyl chain (didodecyldimethyl-ammonium bromide and trioctadecylmetilammonium bromide) as structure-directing agents for the silicon oxide framework. An organic precursor of silicic acid (triethoxymethylsilane) has been used and it was processed by competitive hydrolysis and polycondensation reactions under controlled directions assured by the presence of oriented template. Silica materials thus obtained are used for encapsulation of two flavonoid samples containing as active principles two sources: rutin and a vegetable extract from Begonia plant. The synthesis of encapsulated nanocompounds has been achieved taking into consideration the specific interaction between the colloidal gel precursors and molecular structures of selected biomolecules. The main objective was to improve the encapsulation conditions for specific biomolecules, searching for the highest stability and functionality without loosing the quality of the flavonoid properties, particularly optical properties like fluorescence. The structural properties of the encapsulated samples have been studied by FT-IR and UV-VIS spectroscopy, thermal analysis and SEM/EDX analysis. The fluorescence experiments showed that, in the case of all four encapsulated samples, the fluorescence spectra manifest a significant increase in intensity signals, with more than 10 times for individual flavonoid and 50 times for Begonia extract. This behaviour are mainly assigned to the physical interaction of flavonoid molecules with the residual hydroxyl groups of silica, excellent synergistic properties of silica and the favourable conformation arrangement of organic molecules inside the silica network. The size distribution of synthesised polymeric silica materials have been investigated by dynamic light scattering (DLS) and optical microscopy.

Lacatusu, Ioana; Badea, Nicoleta; Nita, Rodica; Murariu, Alina; Miculescu, Florin; Iosub, Ion; Meghea, Aurelia

2010-04-01

403

Application de la technologie des materiaux sol-gel et polymere a l'optique integree  

NASA Astrophysics Data System (ADS)

With the advancement of optical telecommunication systems, "integrated optics" and "optical interconnect" technology are becoming more and more important. The major components of these two technologies are photonic integrated circuits (PICs), optoelectronic integrated circuits (OEICs), and optoelectronic multichip modules ( OE-MCMs). Optical signals are transmitted through optical waveguides that interconnect such components. The principle of optical transmission in waveguides is the same as that in optical fibres. To implement these technologies, both passive and active optical devices are needed. A wide variety of optical materials has been studied, e.g., glasses, lithium niobate, III-V semiconductors, sol-gel and polymers. In particular, passive optical components have been fabricated using glass optical waveguides by ion-exchange, or by flame hydrolysis deposition and reactive ion etching (FHD and RIE ). When using FHD and RIE, a very high temperatures (up to 1300°C) are needed to consolidate silica. This work reports on the fabrication and characterization of a new photo-patternable hybrid organic-inorganic glass sol-gel and polymer materials for the realisation of integrated optic and opto-electronic devices. They exhibit low losses in the NIR range, especially at the most important wavelengths windows for optical communications (1320 nm and 1550 nm). The sol-gel and polymer process is based on photo polymerization and thermo polymerization effects to create the wave-guide. The single-layer film is at low temperature and deep UV-light is employed to make the wave-guide by means of the well-known photolithography process. Like any photo-imaging process, the UV energy should exceed the threshold energy of chemical bonds in the photoactive component of hybrid glass material to form the expected integrated optic pattern with excellent line width control and vertical sidewalls. To achieve optical wave-guide, a refractive index difference Delta n occurred between the isolated (guiding layer) and the surrounding region (buffer and cladding). Accordingly, the refractive index emerges as a fundamental device performance material parameter and it is investigated using slab wave-guide. (Abstract shortened by UMI.)

Saddiki, Zakaria

2002-01-01

404

Hybrid optics for the visible produced by bulk casting of sol-gel glass using diamond-turned molds  

SciTech Connect

Recent combinations of diffractive and refractive functions in the same optical component allow designers additional opportunities to make systems more compact and enhance performance. This paper describes a research program for fabricating hybrid refractive/diffractive components from diamond-turned molds using the bulk casting of sol-gel silica glass. The authors use the complementary dispersive nature of refractive and diffractive optics to render two-color correction in a single hybrid optical element. Since diamond turning has matured as a deterministic manufacturing technology, techniques previously suitable only in the infrared are now being applied to components used at visible wavelengths. Thus, the marriage of diamond turning and sol-gel processes offers a cost-effective method for producing highly customized and specialized optical components in high quality silica glass. With the sol-gel casting method of replication, diamond-turned mold costs can be shared over many pieces. Diamond turning takes advantage of all of the available degrees of freedom in a single hybrid optical element: aspheric surface to eliminate spherical aberration, kinoform surface for control of primary chromatic aberration, and the flexibility to place the kinoform on non-planar surfaces for maximum design flexibility. The authors discuss the critical issues involved in designing the hybrid element, single point diamond-turning the mold, and fabrication in glass using the sol-gel process.

Bernacki, B.E.; Miller, A.C.; Maxey, L.C.; Cunningham, J.P. [Oak Ridge National Lab., TN (United States); Moreshead, W.V.; Nogues, J.L.R. [Geltech Inc., Alachua, FL (United States)

1995-07-01

405

Gelation of aqueous gelatin solutions. II. Rheology of the sol-gel Madeleine Djabourov, Jacques Leblond and Pierre Papon  

E-print Network

333 Gelation of aqueous gelatin solutions. II. Rheology of the sol-gel transition Madeleine gelatin solutions during the gelation process at several temperatures. The linear viscoelastic regim that gelatin gelation can be interpreted within the framework proposed by de Gennes and Stauffer

Paris-Sud XI, Université de

406

New method of viscosity measurement near the gelatin sol-gel transition J. Dumas and J.-C. Bacri  

E-print Network

L-279 New method of viscosity measurement near the gelatin sol-gel transition J. Dumas and J théorie de la percolation. Abstract. 2014 The viscosity of a 7 % gelatin solution has been measured.30J - 64.70E - 64.80 Gelatin is the water-soluble product of the disso- lution, disorganization

Paris-Sud XI, Université de

407

Magnetic properties of CoFe2O4 thin films prepared by a sol-gel method  

Microsoft Academic Search

Thin films with cobalt ferrite layers on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of the films were investigated with an x-ray diffractometer, a vibrating sample magnetometer and atomic force microscopy. The crystallization temperature for Co ferrite thin films was determined by using Mössbauer spectroscopy. Co ferrite films annealed at and above 450

Jae-Gwang Lee; Jae Yun Park; Young-Jei Oh; Chul Sung Kim

1998-01-01

408

ITO/poly(aniline)/sol-gel glass: An optically transparent, pH-responsive substrate for supported lipid bilayers.  

PubMed

Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4-9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 ?m(2)/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation, and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels. PMID:25328882

Al-Obeidi, Ahmed; Ge, Chenhao; Orosz, Kristina S; Saavedra, S Scott

2013-01-01

409

ITO/poly(aniline)/sol-gel glass: An optically transparent, pH-responsive substrate for supported lipid bilayers  

PubMed Central

Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4–9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 ?m2/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation, and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels. PMID:25328882

Al-Obeidi, Ahmed; Ge, Chenhao; Orosz, Kristina S.; Saavedra, S. Scott

2014-01-01

410

Sol-Gel Application for Consolidating Stone: An Example of Project-Based Learning in a Physical Chemistry Lab  

ERIC Educational Resources Information Center

A Project Based Learning (PBL) methodology was used in the practical laboratories of the Advanced Physical Chemistry department. The project type proposed simulates "real research" focusing on sol-gel synthesis and the application of the obtained sol as a stone consolidant. Students were divided into small groups (2 to 3 students) to…

de los Santos, Desiree´ M.; Montes, Antonio; Sa´nchez-Coronilla, Antonio; Navas, Javier

2014-01-01

411

ELISA AND SOL-GEL BASED IMMUNOAFFINITY PURIFICATION OF THE PYRETHROID BIOALLETHRIN IN FOOD AND ENVIRONMENTAL SAMPLES  

EPA Science Inventory

The peer-reviewed article describes the development of a new sol-gel based immunoaffinity purification procedure and an immunoassay for the pyrethroid bioallethrin. The immunoaffinity chromatography procedure was applied to food samples providing an efficient cleanup prior to im...

412

Effect of Surface Morphology on Crack Growth at a Sol-Gel Reinforced Epoxy/Aluminum Interface  

E-print Network

, USA Douglas H. Berry Jill E. Seebergh Joseph H. Osborne Kay Y. Blohowiak Boeing Company, Seattle Boeing Company, Seattle, WA, USA) [11­14]. Although this pro- cess is similar to the currently used grit-, Washington, USA The Boeing sol-gel conversion coating (Boegel-EPII), derived from an acid- catalyzed aqueous

Chaudhury, Manoj K.

413

A Urea Biosensor from Stacked Sol-Gel Films with Immobilized Nile Blue Chromoionophore and Urease Enzyme  

PubMed Central

An optical urea biosensor was fabricated by stacking several layers of sol-gel films. The stacking of the sol-gel films allowed the immobilization of a Nile Blue chromoionophore (ETH 5294) and urease enzyme separately without the need of any chemical attachment procedure. The absorbance response of the biosensor was monitored at 550 nm, i.e. the deprotonation of the chromoionophore. This multi-layer sol-gel film format enabled higher enzyme loading in the biosensor to be achieved. The urea optical biosensor constructed from three layers of sol-gel films that contained urease demonstrated a much wider linear response range of up to 100 mM urea when compared with biosensors that constructed from 1-2 layers of films. Analysis of urea in urine samples with this optical urea biosensor yielded results similar to that determined by a spectrophotometric method using the reagent p-dimethylaminobenzaldehyde (R2 = 0.982, n = 6). The average recovery of urea from urine samples using this urea biosensor is approximately 103%.

Alqasaimeh, Muawia Salameh; Heng, Lee Yook; Ahmad, Musa

2007-01-01

414

Na-A (LTA) zeolite synthesis directly from alumatrane and silatrane by sol-gel microwave techniques  

E-print Network

Na-A (LTA) zeolite synthesis directly from alumatrane and silatrane by sol-gel microwave techniques 2002; accepted 7 August 2002 Abstract Na-A (1 mm crystal size) zeolite was successfully synthesized via large crystallite sizes ($4.5 mm). The analyzed Si:Al:Na ratio of synthe- sized Na-A zeolite is 1

Gulari, Erdogan

415

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

PubMed

An optical fiber biosensor consisting of acetylcholinesterase (AChE) and bromothymol blue (BTB) doped sol-gel film was employed to detect organophosphate pesticide chlorpyrifos. The main advantage of this optical biosensor is the use of a single sol-gel film with immobilized AChE and BTB. The compatibility of this mixture (AChE and BTB) with the sol-gel matrix has prevented leaching of the film. The immobilization of the enzyme and indicator was simple without chemical modification. The biosensing element on single sol-gel film has been placed inside the flow-cell for flow system. In the presence of a constant AChE, a color change of the BTB and the measured reflected signal at wavelength 622nm could be related to the pesticide concentration in the sample solutions. The performance of optical biosensor in the flow system has been optimized, including chemical and physical parameters. The response time of the biosensor is 8min. A linear calibration curve of chlorpyrifos against the percentage inhibition of AChE was obtained from 0.05 to 2.0mg/L of chlorpyrifos (18-80% inhibition, R(2)=0.9869, n=6). The detection limit for chlorpyrifos was 0.04mg/L. The results of the analysis of 0.5-1.5mg/L of chlorpyrifos using this optical biosensor agreed well with chromatographic method. PMID:18371683

Kuswandi, Bambang; Fikriyah, Chulaifah Indah; Gani, Agus Abdul

2008-01-15

416

Redox-modified silicate films: anthraquinone- and Prussian-blue-modified sol-gel electrodes  

NASA Astrophysics Data System (ADS)

Two types of sol-gel derived redox modified electrodes are introduced. Anthraquinone modified silicate films were produced from 1,5-di-[(3- trimethoxysilyl)propylamino)anthraquinone derived sol by dip- coating of ITO coated microscope slides. The monomer was synthesized from commercially available 3- aminopopyltrimethoxysilane and 1,5-dichloroanthraquinone. Prussian blue modified electrodes were produced by cycling the potential of a preformed, porous Fe2+ doped silicate film coated on ITO substrate in a potassium ferricyanide solution. In both cases, cyclic voltammetry and electronic spectra of the films show that more than 100 layers of redox monomers are electrochemically active, which indicates long range charge transport by electron self exchange mechanism.

Bharathi, Subramanian; Wu, Zhibin; Lev, Ovadia

1997-10-01

417

SrFe 12O 19 prepared by the proteic sol-gel process  

NASA Astrophysics Data System (ADS)

Powders of strontium hexaferrite (SrFe 12O 19) were prepared by the proteic sol-gel process using coconut water as a precursor. X-ray diffraction (XRD) measurement showed the formation of SrFe 12O 19 with a small amount of the hematite for the sample calcined at 1000 °C with Fe/Sr=12. Rietveld refinement disclosed that this sample had 87.56% of the SrFe 12O 19 and 12.44% of Fe 2O 3 and the values for Rp, Rwp and ?2 were 4.28%, 5.93% and 1.71, respectively. The magnetic properties were Ms=64 emu/g, Mr/ Ms=0.55 and Hc=1.4 kOe for a crystallite size of 57 nm.

Brito, P. C. A.; Gomes, R. F.; Duque, J. G. S.; Macêdo, M. A.

2006-10-01

418

Preparation of barium hexaferrite nanopowders by the sol-gel method, using goethite  

NASA Astrophysics Data System (ADS)

A series of barium hexaferrite nanoparticles (BaO· nFe 2O 3) with different n values were prepared by the sol-gel method, using goethite and Ba carbonate as raw materials. Phase identification of the samples was investigated by X-ray diffraction (XRD). XRD investigations show that the samples with n=5 and calcined at temperatures higher than 875 °C are single-phase Ba ferrite. An average crystallite size of 22 nm was obtained for the single-phase sample with minimum calcining temperature of 875 °C, using the Scherrer's formula. The morphology of the samples was checked by transmission electron microscope (TEM) and magnetic properties were measured by a sensitive permeameter. The results show that the samples have nonzero coercivities, which shows the particle size are not less than the critical size of Ba ferrite and then are not superparamagnet.

Mozaffari, M.; Taheri, M.; Amighian, J.

2009-05-01

419

Solar heat reflective glass by nanostructured sol-gel multilayer coatings  

NASA Astrophysics Data System (ADS)

New 3-layer near-infrared reflective glasses were prepared by coating clear float soda-lime glass with nanostructured TiO 2 and SiO 2 films using a dip coating technique. Reflective interference filters at NIR region (800-1000 nm) were designed by simulation and prepared onto 4 mm clear glass. Optical, microstructural and mechanical properties were determined for the coated glasses. 3-layer sol-gel glasses show high visible transmittance >70% combined with high solar reflectance about 30% (with reflectivity up to 60% at region from 800 to 950 nm) and high UV blockage (transmittance <35%). Due to good abrasion resistance of the filters, application for monolithic windows in automotive and architectural areas is promising.

Nagamedianova, Z.; Ramírez-García, R. E.; Flores-Arévalo, S. V.; Miki-Yoshida, M.; Arroyo-Ortega, M.

2011-10-01

420

Modified sol-gel method for patterned lithium niobate thin film preparation  

NASA Astrophysics Data System (ADS)

A key stage in production of the integrated optics devices is forming of microtopography on crystalline films. The current methods generally comprise two separate steps: producing of thin film and creation a topographical pattern on it. But the inherently large chemical stability of crystalline LiNbO3 has effectively precluded the use of standard photolithographic patterning techniques. We present new approach based on the modified sol-gel technology using the photosensitive gel. In this case, the photolithography is used on the stage of dried gel whereupon the direct crystallization of patterned precursor film allows to create integrated optical element without subsequent etching of crystalline film. Presented method of patterned thin film preparation involves synthesis of photo-reactive complex of metal, which undergoes change under the UV light. This technology has allowed to obtain first samples of different types of waveguide devices.

Poghosyan, Armen R.; Guo, Ruyan; Grigoryan, Stepan G.; Manukyan, Aleksandr L.; Vardanyan, Eduard S.

2008-08-01

421

Structural and optical properties of WO3 electrochromic layers prepared by the sol-gel method  

NASA Astrophysics Data System (ADS)

Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel 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 (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline structures for thin film and powdered WO3 were confirmed by XRD analysis. SEM micrograph of annealed samples revealed micro cracks due to a decrease in density and a contraction of layers. EDX analysis showed that 1?2 ratio of oxygen and tungsten atoms in the prepared films is obtained at heat treatment temperatures higher than 200 °C. Furthermore, the annealed samples showed very good electrochromic behavior in cyclic voltammetery studies. Refractive index “n” and extinction coefficient “k” values were found to be reduced by increasing the wavelength and decreasing the temperature.

Novinrooz, Abdoljavad; Sharbatdaran, Masoomeh; Noorkojouri, Hassan

2005-09-01

422

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

NASA Astrophysics Data System (ADS)

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 incorporated into the film structure, which could be associated to the sinterization film process. Other film measurements such as optical properties, XRD, and SEM were performed in order to complement the IBA analysis. The results show that cobalt oxide film coatings prepared by this technique have good optical properties as solar absorbers and potential uses in solar energy applications.

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

2001-07-01

423

The enhancement of benzotriazole on epoxy functionalized silica sol-gel coating for copper protection  

NASA Astrophysics Data System (ADS)

The influence of the amount of benzotriazole (BTA) on the wetting and anticorrosion ability of the epoxy functionalized silica sol-gel (ESol) coating was studied by various complementary methods. IR results demonstrate that BTA reacted with ESol through a 1:1 addition reaction of Nsbnd H to epoxy group. The water contact angle of the ESol coating increases with an increase in the amount of BTA. SEM and adhesion tests reveal that BTA could improve the adhesion of ESol to copper surface. Moreover, the best protection was achieved when the amount of BTA equals to the molar number of epoxy group in the ESol coating according to the results of electrochemical measurements and salt spray test.

Peng, Shusen; Zhao, Wenjie; Li, He; Zeng, Zhixiang; Xue, Qunji; Wu, Xuedong

2013-07-01

424

Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1000 {angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

Pekala, R.W.

1998-04-28

425

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1995-01-01

426

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1996-01-01

427

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes{<=}1000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

Pekala, R.W.

1995-12-19

428

Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

Pekala, Richard W. (Pleasant Hill, CA)

1998-04-28

429

Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures  

DOEpatents

The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1,000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1,050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

Pekala, R.W.

1996-09-17

430

Nanostructured porous sol-gel materials for applications in solar cells engineering  

NASA Astrophysics Data System (ADS)

Two nanostructured Sol-Gel composite materials for application in solar cells engineering were created and studied: the TiO2/SiO2 films for antireflecting coatings of cells, and PMMA/SiO2 insulating layers on metal substrate for efficient heat extraction from a cell. Structural and optical investigation of the first composite proved that its parameters are adequate to serve the purpose; when doped with the dye absorbing UV light and emitting in the visible, it could also increase quantum yield of a cell. The second composite is designed for use in a hybrid PV/Thermal system, where it could optimize the heat exchange between a cell and solar plane collector, which also leads to an increase of efficiency of the system.

Zakharchenko, R. V.; Díaz-Flores, L. L.; Pérez-Robles, J. F.; González-Hernández, J.; Vorobiev, Y. V.

2005-06-01

431

Investigation of the Peroxovanadate Sol-Gel Process and Characterization of the Gels  

SciTech Connect

In general, the peroxovanadate solution sol-gel process can be thought of as consisting of two parts: (1) the decomposition of the peroxo species and (2) cation hydrolysis leading to gelation. By controlling the synthesis conditions, both layered and amorphous compounds can be created. However, the type of water coordination observed in these gels was found to be identical no matter what the long-range order. The current work clarified many of the discrepancies found in the literature and offered much new valuable information. Highlights include the types of vanadium environments present at various stages of hydration, the role of adsorbed water, oxygen exchange from adsorbed water into the gel sites, and the ability to create metastable VMoO solid solution phases. These results could have a variety of impacts on future catalysis research.

Craig Joseph Fontenot

2001-12-31

432

Preparation and reduction behavior of Mo-Cu powders by Sol-Gel  

NASA Astrophysics Data System (ADS)

Mo-Cu composite powders were prepared by the Sol-Gel method using citric acid as chelating reagent. The composition, morphology and particle size of the powders were studied by the XRD and TEM. TEM observation result shows the particle size of Mo-Cu powders is about 150nm after reduction and the Mo grains are covered homogeneously by Cu on the surface. The reduction behavior and mechanism were analyzed systematically. Temperature programmed reduction (TPR) results indicate that the appropriate two-step reduction temperatures are 500°C and 700°C, respectively. The results from FT-IR show that the bond of Mo=O is weakened due to the bond of Cu-O-Mo, which leads to the increase of the reduction capability of the Mo-Cu composite oxide powders.

Zhao, Ming; Wang, Jinshu; Liu, Wei; Zhou, Meiling

2009-09-01

433

The Effect of Time, Temperature and Composition on Boron Carbide Synthesis by Sol-gel Method  

NASA Astrophysics Data System (ADS)

To minimize free carbon residue in the boron carbide (B4C) powder, a modified sol-gel process is performed where the starting materials as boric acid and citric acid compositions are adjusted. Because of boron loss in the form of B2O2(g) during the reduction reaction of the stoichiometric starting composition, the final B4C powders contain carbon residues. Thus, an excess H3BO3 is used in the reaction to compensate the loss and to obtain stoichiometric powders. Parameters of production have been determined using x-ray diffraction analysis and particle size analyses. The synthesized B4C powder using an excess boric acid composition shows no trace of carbon.

Hadian, A. M.; Bigdeloo, J. A.

2008-02-01

434

Modified sol-gel preparation of LiNbO3 target for PLD  

NASA Astrophysics Data System (ADS)

When preparing LiNbO3 thin layer by PLD, the maximal density of polycrystalline target is important. In this work, we prepared the precursor powders by sol-gel method and used them at PLD target synthesis. The gels were synthesized by Pechini polyesterification, using citric acid and ethylene glycol as an organic matrix constituents, and then decomposed using various temperatures (800, 600 and 400 °C) and atmospheres (air, nitrogen and oxygen in sequence). Out of several combinations tested, the decomposition at 800 °C in nitrogen followed by the oxidation at 400 °C in oxygen was found to be the best way to achieve the minimal particle size of powder precursor resulting in denser targets. The prepared targets were characterized by XRD and SEM. The optimized process was subsequently used for preparation of LiNbO3 target. Thin layers prepared by PLD from this target resulted smoother than the layers prepared from commercial monocrystalline target.

Jakeš, V.; Rubešová, K.; Erben, J.; Nekvindová, P.; Jelínek, M.

2013-10-01

435

Impact of temperature on zinc oxide particle size by using sol-gel process  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanoparticles were prepared and synthesized via sol-gel method, by using citric acid as a precursor. The impact of annealing on the particle size was investigated. Based on the results from the Thermogravimetric Analysis (TGA), three different annealing temperature which is 500, 600 and 700 °C were chosen followed by the characterization of the ZnO nanoparticle by using Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopy (FESEM). Results showed that the crystallite size estimated from PXRD increased with the annealing temperature which was hexagonal structure for ZnO. TEM further revealed the same tendency which the Zn NPs size also increased with the annealing temperature.

Lee, Keanchuan; Saipolbahri, Zulhilmi Akmal bin; Guan, Beh Hoe; Soleimani, Hassan; Ching, Dennis Ling Chuan

2014-10-01

436

Structural features of Ce doped YAG nanoparticles synthesized by modified sol-gel method  

NASA Astrophysics Data System (ADS)

Yttrium aluminum garnet (YAG) is an extensively used laser host material. Rare-earth doped YAG nanoparticles are promising phosphor materials for display devices. Ce-doped YAG nanoparticles were synthesized by modified sol-gel technique in an aqueous media using citric acid and ethylene glycol as chelating agents. Single phase nanocrystalline material was obtained at 850 °C. It is much lower temperature compared to other similar techniques used for preparing nanoparticles of YAG. The Ce-doping concentration was optimized and kept at 1 mol%. The prepared material was annealed at different temperatures and were characterized by XRD, SEM and TEM techniques to establish the particle sizes and structure. Average particle sizes were found ranging ?20-50 nm.

Kaithwas, N.; Dave, M.; Kar, S.; Bartwal, K. S.

2012-04-01

437

Spin-Coated Erbium-Doped Silica Sol-Gel Films on Silicon  

E-print Network

This work reports optical functionality contained in, as well as and produced by, thin film coatings. A sol-gel process, formulated with precursor active ingredients of erbium oxide and tetraethylorthosilicate (TEOS), was used for spin-coating thin (~130 nm) erbium-doped (~6 at. %) silica films on single-crystal silicon. Annealed films produce infrared emission in the 1.5-micron band from erbium ions in the film, as well as greatly enhancing (~100X) band-gap emission from the underlying silicon. The distinctly different mechanisms for the two modes of optical activities are interpreted in terms of optical emission theory and modeling; prospects for opto-electronic applications are discussed.

Abedrabbo, Sufian; Shet, Sudhakar; Fiory, Anthony; Ravindra, Nuggehalli

2012-01-01

438

Sol–gel synthesis of Ce-substituted BaFe 12 O 19  

Microsoft Academic Search

Ce-substituted BaFe12O19 (BaCe\\u000a x\\u000a Fe12?x\\u000a O19, x = 0, 0.01, 0.03, 0.05) was prepared by citrate sol–gel method. The thermal decomposition process of precursor was investigated\\u000a by TG-DSC. The phase composition of the BaCe\\u000a x\\u000a Fe12?x\\u000a O19 was characterized by X-ray powder diffraction analysis (XRD) which reveals that the BaCe\\u000a x\\u000a Fe12?x\\u000a O19 crystallizes in a hexagonal structure. The lattice parameter of

Chang Sun; Kangning Sun

2007-01-01

439

Mechanical properties of sol–gel derived SiO2 nanotubes  

PubMed Central

Summary The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values from the nanoindentation data. Finally, the Young’s moduli of SiO2 NTs measured by different methods were compared and discussed. PMID:25383292

Antsov, Mikk; Vlassov, Sergei; Dorogin, Leonid M; Vahtrus, Mikk; Zabels, Roberts; Lange, Sven; Lõhmus, Rünno

2014-01-01

440

nanoflakes prepared via a two-step sol-gel-exfoliation method  

NASA Astrophysics Data System (ADS)

The morphology and electrical properties of orthorhombic ?-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that ?-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures.

Zhuiykov, Serge; Kats, Eugene

2014-08-01

441

Synthesis and photoluminescence property of nanostructured sol-gel antimony tin oxide film on silica glass  

NASA Astrophysics Data System (ADS)

Sol-gel based spin coated nanostructured films of tetragonal phase of antimony (10 at%) doped tin oxide (ATO) were prepared on silica glass. XRD and TEM images identify the crystallite size lying in the range, ?3.4-9.8 nm. Quantum confinement was observed in the nanoclusters. Evaluated band gaps at 3.62 eV correspond to the transition for bulk ATO and 4.51 eV, 5.26 eV for excitons and oxygen deficiency. Schemes have been proposed for absorption and photoluminescence excitation (PLE). Two excitonic transitions were observed at 275 nm and 310 nm for different nanocluster sizes. Evaluation of mean free path and Fermi energy correspond to ionized scattering and degeneracy of the ATO films.

Dua, Laxmikanta; Biswas, Prasanta K.

2013-05-01

442

Structural, electrical and magnetic properties of Ni2+ substituted cobalt nanoferrite using sol-gel method  

NASA Astrophysics Data System (ADS)

Ni doped cobalt ferrite of chemical formula Ni(1-x)CoxFe2O4 with x values = 1, 0.5, 0 were prepared by using Poly Vinyl Alcohol (PVA) sol-gel method. The prepared samples were heat treated at 450°C for an hour and grounded to form fine powder. XRD of the powder sample confirms the formation of spinel ferrite phase. SEM and EDAX spectrum reveals the surface and chemical composition of the sample. FTIR spectra of the samples show the stretching vibration of the tetrahedral (?1) and octahedral (?2) bands of Fe-O bonds appearing at 600cm-1 and 424cm-1 respectively. Room temperature magnetic and electrical studies were done using VSM and LCZ meter to analyze their property respectively.

Blessington Selvadurai, A. Paul; Gazzali, P. M. Md.; Murugasen, C.; Pazhanivelu, V.; Murugaraj, R.; Chandrasekaran, G.

2013-02-01

443

Chemical tailoring of hybrid sol-gel thick coatings as hosting matrix for functional patterned microstructures.  

PubMed

A phenyl-based hybrid organic - inorganic coating has been synthesized and processed by hard X-ray lithography. The overall lithography process is performed in a two-step process only (X-rays exposure and chemical etching). The patterns present high aspect ratio, sharp edges, and high homogeneity. The coating has been doped with a variety of polycyclic aromatic hydrocarbon functional molecules, such as anthracene, pentacene, and fullerene. For the first time, hard X-rays have been combined with thick hybrid functional coatings, using the sol-gel thick film directly as resist. A new technique based on a new material combined with hard X-rays is now available to fabricate optical devices. The effect due to the high-energy photon exposure has been investigated using FT-IR and Raman spectroscopy, laser scanner, optical profilometer, and confocal and electron microscope. High-quality thick hybrid fullerene-doped microstructures have been fabricated. PMID:21218788

Falcaro, Paolo; Costacurta, Stefano; Malfatti, Luca; Buso, Dario; Patelli, Alessandro; Schiavuta, Piero; Piccinini, Massimo; Grenci, Gianluca; Marmiroli, Benedetta; Amenitsch, Heinz; Innocenzi, Plinio

2011-02-01

444

Boron doping effects in electrochromic properties of NiO films prepared by sol-gel  

SciTech Connect

In this paper, NiO films doped with B{sub 2}O{sub 3} were first prepared by sol-gel. The effects of boron content on the structure and electrochromic properties of NiO films were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetric (CV) and UV-vis spectrophotometer, respectively. In addition, the roughness and phase of the bleached/colored were studied by atom force microscopy (AFM). B-doped prevent the crystallization of the films. The colored state transmittance could be significantly lowered when the boron added. The NiO film doped with boron exhibited a noticeable electrochromism with a variation of transmittance up to {proportional_to}60% at the wavelength range of 300-500 nm. (author)

Lou, Xianchun; Zhao, Xiujian; He, Xin [Key Laboratory of Silicate Materials Science and Engineering, Wuhan University of Technology, Ministry of Education, 122 Luoshi Road, Hongshan District, Wuhan, Hubei 430070 (China)

2009-12-15

445

Thermoluminescent properties of sol-gel-produced (MgO)x:(SiO2)y compounds  

NASA Astrophysics Data System (ADS)

In this work we present the results on synthesis of sol-gel produced compounds containing SiO2 and MgO in different stoichiometric proportions. Tetraethoxy silane (TEOS), magnesium acetate, and dysprosium nitrate were used as precursors. After hydrolysis of TEOS in ethanol solution the other precursors dissolved in ethanol were added. After several hours the gelation process occurred, and transparent glass was formed. Subsequent heating at temperatures up to 1050°C led to formation of compounds containing SiO2 and MgO: enstatite and forsterite. We checked the formation of relevant phases by means of X-ray powder diffraction. Thermoluminescent properties of the obtained compounds were checked after doping them with dysprosium ions. Linear response of thermoluminescent properties on gamma irradiation was found, but the sensitivity of phosphors obtained in this way was rather moderate comparing with other well known thermoluminescent phosphors.

Klosowicz, Stanislaw J.; Furtak, Piotr; Michalski, Edward; Majchrowski, Andrzej

2003-10-01

446

Towards new levels for stacking of sol-gel functional coatings  

NASA Astrophysics Data System (ADS)

High optical performance coatings prepared by a liquid deposition process have been studied with focus on the parameters playing a role on the layer stacking ability. During the development of multilayer optical coatings, defects such as cracks, scattering and a refractive index gradient could appear. In order to understand the origins of these limitations, the investigation was performed on colloidal stacks of single and multi-materials. This study has rendered it possible to define the main process parameters as well as the physical and chemical parameters of the suspensions influencing the stacking capacity. This work is a first step to obtaining evidence of a relationship between the thin film microstructure induced by deposition conditions and the ability to achieve sol-gel thick films with good optical (homogeneous) and mechanical (crack-free) properties.

Dieudonné, X.; Vallé, K.; Belleville, P.

2011-08-01

447

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis  

DOEpatents

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

1998-09-29

448

Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis  

DOEpatents

A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

Martino, Anthony (Albuquerque, NM); Yamanaka, Stacey A. (Dallas, TX); Kawola, Jeffrey S. (Albuquerque, NM); Showalter, Steven K. (Albuquerque, NM); Loy, Douglas A. (Albuquerque, NM)

1998-01-01

449

Sol-gel synthesis of hybrid organic-inorganic materials. Hexylene- and phenylene-bridged polysiloxanes  

SciTech Connect

New highly cross-linked polysiloxanes were prepared by sol-gel polymerization of 1,6-bis(diethoxymethylsilyl)hexane (1) and 1,4-bis(diethoxymethylsilyl)benzene (2). Hydrolysis and condensation of 1 and 2 under acidic and basic conditions with 4 equiv of water led to the rapid formation of hexylene- and phenylene-bridged polysiloxane gels. The dry gels (xerogels) were intractable, insoluble materials that were noticeably hydrophobic, exhibiting no swelling in organic solvents or water. Most of the xerogels were high surface area, mesoporous materials. Hexylene-bridged polysiloxanes prepared under acidic conditions were always nonporous regardless of whether they were processed to afford xerogels or supercritically dried as aerogels. Hexylene-bridged polysiloxanes prepared under basic conditions and all of the phenylene-bridged polysiloxanes were mesoporous with surface areas as high as 1025 m{sup 2}/g. 35 refs., 9 figs., 3 tabs.

Loy, D.A.; Jamison, G.M.; Baugher, B.M.; Myers, S.A.; Assink, R.A.; Shea, K.J. [Sandia National Laboratories, Albuquerque, NM (United States)] [Sandia National Laboratories, Albuquerque, NM (United States); [Univ. of California, Irvine, CA (United States)

1996-03-01

450

Sol-gel kinetics: /sup 29/Si NMR (nuclear magnetic resonance) and a statistical reaction model  

SciTech Connect

The early time behavior of an acid catlayzed Si(OCH/sub 3/)/sub 4/ (TMOS) sol-gel was studied by high resolution /sup 29/Si nuclear magnetic resonance (NMR). Both the water producing and the alcohol producing condensation reactions were found to contribute significantly to the overall condensation rate. A general theoretical kinetic formalism which specifically treats the temporal evolution of the various chemical function groups about a specific slilcon atom was developed. The experimentally observed functional group distribution was in agreement with the distribution predicted by a simplified statistical reaction model. The mathematical framework for the study of chemical speciation at the next-to-nearest functional group level was developed. This framework was used to assign several fine structure resonances, and to show that the formation of various dimeric species is also largely statistical in nature. 17 refs., 6 figs.

Assink, R.A.; Kay, B.D.

1988-01-01

451

Sol-gel/rhodamine 6G composite films with tailored microstructures  

SciTech Connect

A multi-step hydrolysis procedure was developed to prepare composite organic dye/sol-gel thin films with variable porosity for such as switches or sensors. Variation of acid and base catalyzed hydrolysis sequences of three sols prepared from tetraethoxysilane with identical H{sub 2}O/Si ratios, dilution factors, and pH resulted in considerably different silicate speciation. Under conditions where monomer was avoided, the refractive indices of as-deposited films could be varied by an again step prior to film deposition. This general strategy, which relies on the aggregation of fractal polymeric clusters, is compatible with the low temperature and near neutral pH requirements of both organic dyes and biologically active species such as enzymes.

Logan, D.L.; Ashley, C.S.; Assink, R.A.; Brinker, C.J. [Sandia National Labs., Albuquerque, NM (United States)]|[New Mexico Univ., Albuquerque, NM (United States). Center for Micro-Engineered Ceramics

1992-12-31

452

Sol-gel/rhodamine 6G composite films with tailored microstructures  

SciTech Connect

A multi-step hydrolysis procedure was developed to prepare composite organic dye/sol-gel thin films with variable porosity for such as switches or sensors. Variation of acid and base catalyzed hydrolysis sequences of three sols prepared from tetraethoxysilane with identical H[sub 2]O/Si ratios, dilution factors, and pH resulted in considerably different silicate speciation. Under conditions where monomer was avoided, the refractive indices of as-deposited films could be varied by an again step prior to film deposition. This general strategy, which relies on the aggregation of fractal polymeric clusters, is compatible with the low temperature and near neutral pH requirements of both organic dyes and biologically active species such as enzymes.

Logan, D.L.; Ashley, C.S.; Assink, R.A.; Brinker, C.J. (Sandia National Labs., Albuquerque, NM (United States) New Mexico Univ., Albuquerque, NM (United States). Center for Micro-Engineered Ceramics)

1992-01-01

453

Application of sol-gel techniques to thin-film superconductor systems  

SciTech Connect

This paper discusses the preparation and characterization of sol-gel produced thin films for barrier layer and high T{sub c} superconductor applications. Hydrolyzed metal alkoxide solutions were spin coated on Si substrates with subsequent thermal processing. Barrier layers of alkaline earth oxides, perovskites, Y{sub 2}O{sub 3}, ZrO{sub 2} and others were produced. Characterization was performed via SEM, XRD, ESCA, Auger depth profiling and four point probe resistivity measurements for 1-2-3 thin films. On Si wafers, barrier layer films were fairly smooth with some cracking and pitting present. Si migration was severe for alkaline earth thin films on Si wafers. Some perovskite films on Si showed formation of Ba-Si-O phases at the Si interface.

Wandass, J.H.; Cambria, F.M.; Whitwell, G.E. (Akzo Chemicals Inc., Akzo Research Laboratory Dobbs Ferry, Livingston Ave., Dobbs Ferry, NY (USA))

1990-01-25

454

Sol-gel synthesis and densification of aluminoborosilicate powders. Part 1: Synthesis  

NASA Technical Reports Server (NTRS)

Aluminoborosilicate powders high in alumina content were synthesized by the sol-gel process utilizing various methods of preparation. Properties and microstructural effects related to these syntheses were examined. After heating to 600 C for 2 h in flowing air, the powders were amorphous with the metal oxides comprising 87 percent of the weight and uncombusted organics the remainder. DTA of dried powders revealed a T(sub g) at approximately 835 C and an exotherm near 900 C due to crystallization. Powders derived from aluminum secbutoxide consisted of particles with a mean diameter 5 microns less than those from aluminum isopropoxide. Powders synthesized with aluminum isopropoxide produced agglomerates comprised of rod shaped particulates while powders made with the secbutoxide precursor produced irregular glassy shards. Compacts formed from these powders required different loadings for equivalent densities according to the method of synthesis.

Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

1992-01-01

455

Photoluminescence from terbium doped silica-titania prepared by a sol-gel method  

SciTech Connect

Terbium doped (0.5 at.%) TiO{sub 2}-SiO{sub 2} (30%/70%) was prepared by a sol-gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the powder calcined at two different temperatures. At a low temperature of 550 deg. C an amorphous phase was obtained, but at a higher temperature of 1000 deg. C, the anatase TiO{sub 2} phase was crystallized in the amorphous SiO{sub 2} p