Home About us Contact
|
Home About us Contact | ||
|
|
||
Gel Method (gel + method)
Selected AbstractsHydroxyapatite/Bioactive Glass Films Produced by a Sol,Gel Method: In Vitro BehaviorADVANCED ENGINEERING MATERIALS, Issue 11 2009Nihat C. Köseo Abstract Hydroxyapatite (HA) and HA/bioactive glass (49S) films were deposited on Si(100) substrates by a sol,gel dip-coating method. The microstructure and in vitro bioactivity of the films were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Polycrystalline HA and amorphous bioactive glass films were obtained after annealing at 600 and 400,°C, respectively. The crystallization temperature of HA was determined to be around 568,°C. The surfaces of the HA films were covered with an apatite layer consists of spherulites formed by nanosized needle-like aggregates after the soaking in simulated body fluid (SBF) for 10 days, while amorphous HA/bioactive glass surface was covered with larger spherical crystallites. Both XPS and EDS results obtained from HA/bioactive glass film, after soaking in SBF, showed increasing P amounts on the surface at the expense of Si. The higher density of the newly formed layer on HA/bioactive glass surface than that of the HA surface after 10 days of soaking was evidence of increased reaction rate and apatite forming ability when bioactive glass layer is present on the HA films. [source] Microstructural Study of Mn and Si Co-substituted Hydroxyapatite Thin Films Produced by a Sol,Gel MethodADVANCED ENGINEERING MATERIALS, Issue 7 2009Aligül Büyükaksoy Microstructural changes in sol,gel derived hydroxyapatite thin films associated with Mn and Si co-substitution are investigated. The apatite-forming ability of fabricated thin films in simulated body fluid are found to be affected by changes in the crystallinity and formation of a more dissolvable calcium phosphate phase. [source] Novel Fabrication of Size-Tunable Silica Nanotubes Using a Reverse- Microemulsion-Mediated Sol,Gel Method ,ADVANCED MATERIALS, Issue 9-10 2004J. Jang Size-tunable silica nanotubes have been fabricated using a novel reverse-microemulsion-mediated sol,gel method (see Figure). This facile approach is adaptable to large-scale fabrication, and the diameter of silica nanotubes is tunable through the use of different apolar solvents. The photoluminescence spectrum of the nanotubes displays three emission bands, including a stable and strong blue light emission at 435 nm. [source] Ionic Conductivity Enhancement of La2Mo2,xWxO9 Nanocrystalline Films Deposited on Alumina Substrates by the Sol,Gel MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Zhong Zhuang Dense, crack-free, and uniform La2Mo2,xWxO9 (x=0, 0.1, and 0.2) nanocrystalline films were successfully synthesized on poly-alumina substrates via a modified sol,gel method, with inorganic salt of La(NO3)3·6H2O, (NH4)6Mo7O24·4H2O, and (NH4)6H2W12O24 as precursors. Pure La2Mo2O9 phase was confirmed by X-ray diffractometer when the annealing temperature was >500°C. The average grain size of the La2Mo2,xWxO9 films is in the range of 90,400 nm, depending upon the conditions of thermal treatment, and the thickness of films can reach 1 ,m by repetitive spin-coating. The electrical conductivity increases with decreasing grain size and reaches 0.074 S/cm at 600°C in the film with a grain size of 90 nm, which is one order of magnitude higher than that in the corresponding bulk materials. W-doping can suppress the phase transition that occurs at 580°C in pure La2Mo2O9 and enhance the low-temperature ionic conductivity. Furthermore, the activation energy of conductivity in the nanocrystalline La2Mo2O9 films decreases to about 0.6 eV in comparison with 1.0 eV in the bulk ones, which implies that the grain resistance prevails in the total resistance, when grain size reduces to nanometer domain. [source] Yttrium Silicate Powders Produced by the Sol,Gel Method, Structural and Thermal CharacterizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Damien Boyer Yttrium silicate (Y2SiO5) powders of high purity have been synthesized using the sol,gel method. Alkoxide precursors were used with commercial tetraethyl orthosilicate as the silica source and yttrium propoxide synthesized from YCl3. Powders calcined from the xerogel showed submicrometer crystal sizes. These powders were sintered at temperatures <1300°C and are suitable for coating applications such as a thermal barrier system for SiC/SiC composites. [source] Synthesis and characterization of fine lithium niobate powders by sol- gel methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2007L. H. Wang Abstract Lithium niobate (LN) nanocrystal powders were prepared by low-temperature sol-gel method. Dihydrate lithium acetate as lithium source, and niobium chloride as niobium source were used as starting materials. The gel and powders were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electronmicroscopy (TEM) and Fourier transform infrared (FTIR) spectra. The results show that when the gel was heat-treated at 600°C, the fine LN nanocrystals with the size of 40-60 nm were obtained, and the size of the powders become larger with the heat-treated temperature increasing. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Concentric Sub-micrometer-Sized Cables Composed of Ni Nanowires and Sub-micrometer-Sized Fullerene Tubes,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2007F. Tao Abstract Highly ordered arrays of submicrometer-sized coaxial cables composed of submicrometer-sized C60 and C70 tubes filled with Ni nanowires are successfully prepared by combining a sol,gel method with an electrodeposition process. The wall thickness of the submicrometer-sized tubes can be adjusted by the concentration of fullerenes and the immersion time. The thermal stability of the submicrometer-sized C60 tubes is studied by Raman spectroscopy and it is found that these structures can be easily decomposed to form carbon nanotubes at relatively low temperatures (above 573,K) in an alumina template. These novel coaxial cable structures have been characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), field-emission SEM (FESEM), Raman spectroscopy, elemental mapping, energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) experiments, and superconducting quantum interference device (SQUID) measurements. Magnetic measurements show that these submicrometer-sized cables exhibit enhanced ferromagnetic behavior as compared to bulk nickel. Moreover, submicrometer-sized C70/Ni cables show uniaxial magnetic anisotropy with the easy magnetic axis being parallel to the long axis of the Ni nanowires. C70/Ni cables also exhibit a new magnetic transition at ca.,10,K in the magnetization,temperature (M,T) curve, which is not observed for the analogous C60/Ni structures. The origin of this transition is not yet clear, but might be related to interactions between the Ni nanowires and C70 molecules. There is no preferred magnetization axis in submicrometer-sized C60/Ni cables, which implies that the Ni nanocrystals have different packing modes in the two composites. These different crystalline packing modes lead to different magnetic anisotropy in the two composites, although the Ni nanocrystals have the same face-centered cubic (fcc) structure in both cases. [source] Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous AluminaADVANCED MATERIALS, Issue 13 2010Quan Yuan Homogeneously dispersed ceria nanocatalyst can be synthesized and stabilized with ordered mesoporous alumina by a one-step sol,gel method. This novel material possesses high thermal stability and exhibits 100% conversion at room temperature for CO oxidation when loaded with Au. This established approach can be expanded to the controlled synthesis and stabilization of other nanocatalysts with wide applications. [source] Fabrication and Tunable Dielectric Properties of (Ba0.7Sr0.3)TiO3 -Glass-Based Thick-Film CapacitorsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009Pulipparambil Vasu Divya Ferroelectric glass,ceramics of composition 0.90 (Ba0.7Sr0.3) TiO3,0.10(B2O3:SiO2) (0.90 BST:0.10 BS) synthesized by sol,gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass,ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass,ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm. [source] The Electrophoretic Deposition of Lanthanum Manganite Powders for a Cathode-Supported Solid Oxide Fuel Cell in Planar and Tubular ConfigurationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2008Ivana Krklju The purpose of this research was to obtain porous, high-quality cathodes for solid oxide fuel cells in both planar and tubular shapes. To accomplish this, cathodic electrophoretic deposition of the LaMnO3 powder (synthesized by the modified sol,gel method proposed by Pechini) was performed. The optimal sintering temperatures were 1200°C and 1300°C for the tubular and planar configurations, respectively. Single-phase deposits with about 40% porosity were obtained in both configurations. The cathode quality was confirmed by depositing an electrolyte layer of YSZ. After the cosintering of both layers, an extremely dense electrolyte layer was obtained, and the cathode layer retained its high porosity. [source] Novel Fabrication of Size-Tunable Silica Nanotubes Using a Reverse- Microemulsion-Mediated Sol,Gel Method ,ADVANCED MATERIALS, Issue 9-10 2004J. Jang Size-tunable silica nanotubes have been fabricated using a novel reverse-microemulsion-mediated sol,gel method (see Figure). This facile approach is adaptable to large-scale fabrication, and the diameter of silica nanotubes is tunable through the use of different apolar solvents. The photoluminescence spectrum of the nanotubes displays three emission bands, including a stable and strong blue light emission at 435 nm. [source] Esterification of n -butyric acid with n -butyl alcohol and transesterification of (R,,S)-phenylethanol by lipase immobilized on cellulose acetate,TiO2 gel fibreJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002Yuko Ikeda Abstract Lipase (EC 3.1.1.3) was immobilized on cellulose acetate,TiO2 gel fibre by the sol,gel method. The immobilized lipases were used for esterification of n -butyric acid with n -butyl alcohol and enantioselective acylation of (R, S)-phenylethanol using vinyl acetate as an acyl donor. Compared with native lipase, the activity of the immobilized lipase was stable and relatively unaffected by the water content of the solvent and the substrate concentration. The data indicate that the lipases are immobilized on the fibre surface and that enzyme activity is influenced by bound water. However, the thermal reactivity and enantioselectivity of the immobilized lipase were less than those of native lipase. This may not reflect thermal inactivation of the enzyme but rather significant thermal contraction of the gel fibre by cellulose crystallization, resulting in liberation of bound water and a decrease in the amount of enzyme which is available for the reaction. Copyright © 2001 Society of Chemical Industry [source] Evaluation of a modified IAT-gel with polyethylenglycol (PEG) addition method for red blood cell antibody identificationJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 3 2004L. Gustafsson Abstract We aimed to evaluate whether a PEG-IAT method, modified for gel technique, could replace the two-stage enzyme method for routine identification of red blood cell (RBC) antibodies. A total of 161 selected patient samples were analyzed with the two-stage enzyme tube technique and the PEG-IAT in gel techniques. In 65 samples, identical antibody results were obtained by the two methods. An additional 28 antibodies were identified by either the PEG-IAT gel method or the enzyme method. Twenty antibodies were identified by the PEG-IAT gel method only (12 Rh antibodies, four anti-Kell, two anti-Fya, two anti-Jka), and eight antibodies by the enzyme method only (four Rh antibodies, one anti-K, one anti-Jka, two anti-Lea). The results in the remaining 68 samples were judged as nonspecific reactions, which were more common when the enzyme method was used. We concluded that the PEG-IAT in gel method identifies more RBC antibodies with less nonspecific reactions than the two-stage enzyme technique. However, no single method detected all clinical significant RBC antibodies. J. Clin. Lab. Anal. 18:165,169, 2004. © 2004 Wiley-Liss, Inc. [source] Characteristics of ammonia permeation through porous silica membranesAICHE JOURNAL, Issue 5 2010Masakoto Kanezashi Abstract A sol,gel method was applied for the preparation of silica membranes with different average pore sizes. Ammonia (NH3) permeation/separation characteristics of the silica membranes were examined in a wide temperature range (50,400°C) by measurement of both single and binary component separation. The order of gas permeance through the silica membranes, which was independent of membrane average pore size, was as follows: He > H2 > NH3 > N2. These results suggest that, for permeation through silica membranes, the molecular size of NH3 is larger than that of H2, despite previous reports that the kinetic diameter of NH3 is smaller than that of H2. At high temperatures, there was no effect of NH3 adsorption on H2 permeation characteristics, and silica membranes were highly stable in NH3 at 400°C (i.e., gas permeance remained unchanged). On the other hand, at 50°C NH3 molecules adsorbed on the silica improved NH3 -permselectivity by blocking permeation of H2 molecules without decreasing NH3 permeance. The maximal NH3/H2 permeance ratio obtained during binary component separation was ,30 with an NH3 permeance of ,10,7 mol m,2 s,1 Pa,1 at an H2 permeation activation energy of ,6 kJ mol,1. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Synthesis, characterization, and properties of novel ladderlike phosphorus-containing polysilsesquioxanesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2003Chin-Lung Chiang Abstract Novel ladderlike polysilsesquioxanes that contain phosphorus were successfully synthesized by the sol,gel method. The polysilsesquioxanes were characterized by Fourier transform infrared spectroscopy, 29Si NMR, and X-ray diffraction. The characterizations demonstrated that the polymer possesses a typical ladderlike structure. The thermogravimetric and differential scanning calorimetric data revealed that the polysilsesquioxanes possess excellent thermal stability. A kinetic analysis of thermal degradation showed that the activation energy of thermal degradation is 187 kJ/mol, according to Kissinger's method. The activation energy of thermal degradation normally increases with conversion (from 171 to 309 kJ/mol) according to Ozawa's method. The average activation energy, calculated by Ozawa's method, was 209 kJ/mol. The scanning electron microscopic photograph and Si and P mappings of ladderlike polysilsesquioxanes showed that the particles were uniformly dispersed at the molecular level and that the sizes of the polysilsesquioxane particles were less than 100 nm. The ultraviolet,visible spectra of the ladderlike polysilsesquioxanes revealed no absorbance in the range of 400,800 nm. Ladderlike polysilsesquioxanes possess excellent optical transparency and excellent flame retardance. This transmittance may be used as a criterion for identifying the formation of a homogeneous phase. These polymers have great potential in waveguide applications. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1371,1379, 2003 [source] Effect of lanthanum substitution on the Raman spectra of barium titanate thin filmsJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2007P. S. Dobal Abstract Thin films of Ba1,xLaxTiO3 on platinum substrates were synthesized using the sol,gel method for x values of 0.0, 0.03, 0.05, and 0.10, and the effect of trivalent La3+ substitution on the structural and dielectric properties was studied. Using X-ray diffraction, structural analysis of these compositions revealed a slight increase in the tetragonal distortion of the unit cell with increase in La content. Accordingly, an increase in the tetragonal to cubic transition temperature TT/C was detected by temperature-dependent Raman spectroscopy in the range of 70,500 K. Unlike the results from Raman scattering for the La-doped BaTiO3 films, the dielectric measurements showed broad and diffused dielectric maxima, making the estimation of the transition temperature merely qualitative. Copyright © 2006 John Wiley & Sons, Ltd. [source] Development of a silica monolith microbioreactor entrapping highly activated lipase and an experiment toward integration with chromatographic separation of chiral estersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Koei Kawakami Abstract Microbioreactors are effective for high-throughput production of expensive products from small amounts of substrates. Lipases are versatile enzymes for chiral syntheses, and are highly activated when immobilized in alkyl-substituted silicates by the sol,gel method. For practical application of sol,gel immobilized lipases to a flow system, a microbioreactor loaded with a macroporous silica monolith is well suited, because it can be easily integrated with a chromatographic separator for optical resolution. We attempted to develop a microbioreactor containing a silica monolith-immobilized lipase. A nonshrinkable silica monolith was first formed from a 4:1 mixture of methyltrimethoxysilane (MTMS) and tetramethoxysilane (TMOS). It was then coated with silica precipitates entrapping lipase, derived from a 4:1 mixture of n -butyltrimethoxysilane (BTMS) and TMOS. As a result, monolith treated with the BTMS-based silicate entrapping lipase exhibited approximately ten times higher activity than nontreated monolith-immobilized lipase derived from the MTMS-based silicate, in transesterification between glycidol and vinyl n -butyrate in isooctane. A commercially available chiral column was connected in series to the monolith microbioreactor, and a pulse of substrate solution was supplied at the inlet of the reactor. Successful resolution of the racemic ester produced was achieved in the chromatographic column. [source] Fabrication and Tunable Dielectric Properties of Magnesium-Doped Lead Barium Zirconate Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Xihong Hao In present work, (Pb0.50Ba0.50)ZrO3 (PBZ) thin films doped by Mg from 0 to 5 mol% were deposited on Pt(111)/TiO2/SiO2/Si substrates by the sol,gel method. The phase structure of the Mg-doped PBZ thin films were characterized by X-ray diffraction. The electric-field and temperature-dependent electrical properties of the Mg-doped PBZ thin films were also investigated in detail. It was found that the Mg content had a strong influence on the dielectric properties of the thin films. The maximum values of dielectric permittivity and dielectric loss were obtained with 1 mol% Mg-doping PBZ thin films. However, the figure of merit (FOM) of the films was improved with increase in the Mg content. [source] Physical and Electrical Properties of Nanosized Mn- and Cr-Doped Strontium Y-Type Hexagonal FerritesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Muhammad Javed Iqbal Nanometer-sized crystallites of Y-type strontium hexaferrite, Sr2Ni2Fe12O22 and its Mn- and Cr-doped derivatives have been synthesized by the sol,gel method. Y-type phase formation was achieved at a considerably lower temperature of 950°C than is required in the traditional solid-state method (1200°C). The effect of doping of manganese at the tetrahedral site, Sr2Ni2,xMnx Fe12O22 (x=0.0,2.0), and chromium at octahedral site, Sr2Ni2 Fe12,yCryO22 (y=0.0,1.5), has been studied. The crystal structure remains unaffected by the substitutions. The crystallite size in the range of 13,45 nm is calculated from the X-ray diffraction data. The energy-dispersive X-ray fluorescence analysis shows that Y-type hexaferrites can be prepared with a base of strontium. The extent of doped Cr+3 ions at the octahedral site has been increased from the reported maximum value of y=1.5. Scanning electron micrographs of the samples showed a homogenous microstructure. The dc electrical resistivity studies show that these hexaferrites exhibit high resistivity at room temperature. Cr-doped samples have comparatively higher resistivity than Mn-doped samples. The doubly doped (Cr+Mn) samples possess high resistivity (7.37 × 109,-cm), a low dielectric constant (33.88 at 3000 Hz), and a high Curie temperature (>698 K). The dielectric energy losses are minimized by increasing the Mn and Cr contents of the synthesized samples. [source] A Potential Red-Emitting Phosphor BaGd2(MoO4)4:Eu3+ for Near-UV White LEDJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Chongfeng Guo Red-emitting phosphor BaGd2,xEux(MoO4)4 has been successfully synthesized by a simple sol,gel method. The process of phosphor formation is characterized by thermogravimetric-differential thermal analysis and X-ray diffraction. Field-emission scanning electronic microscopy is used to characterize the size and the shape of the phosphor particles. Photo-luminescent property of the phosphor is also performed at the room temperature. The effects of firing temperature and Eu3+ activator concentration on the photoluminescence (PL) properties are elaborated in detail. PL characterization reveals that the sample with the firing temperature at 800°C and the concentration of Eu3+ at 0.7 shows the most intense emission, and its intensity is about three times stronger than that of phosphor prepared by solid-state method with the same composition and firing temperature. The new red-emitting phosphor shows an intense absorption at 396 nm, which matches well with commercial near-UV light-emitting diode (LED) chips, therefore, it is a good candidate of red phosphor used for near-UV white LEDs. [source] Preparation and Electrical Properties of New Oxide Ion Conductors Ce6,xGdxMoO15,, (0.0,x,1.8)JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009Defeng Zhou A series of oxide ion conductors Ce6,xGdxMoO15,, (0.0,x,1.8) have been prepared by the sol,gel method. Their properties were characterized by differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), Raman, IR, X-ray photoelectron spectroscopy (XPS), and AC impedance spectroscopy. The XRD patterns showed that the materials were single phase with a cubic fluorite structure. The conductivity of Ce6,xGdxMoO15,, increases as x increases and reaches the maximum at x=0.15. The conductivity of Ce4.5Gd1.5MoO15,, is ,t=3.6 × 10,3 S/cm at 700°C, which is higher than that of Ce4.5/6Gd1.5/6O2,, (,t=2.6 × 10,3 S/cm), and the corresponding activation energy of Ce4.5Gd1.5MoO15,, (0.92 eV) is lower than that of Ce4.5/6Gd1.5/6O2,, (1.18 eV). [source] Ionic Conductivity Enhancement of La2Mo2,xWxO9 Nanocrystalline Films Deposited on Alumina Substrates by the Sol,Gel MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Zhong Zhuang Dense, crack-free, and uniform La2Mo2,xWxO9 (x=0, 0.1, and 0.2) nanocrystalline films were successfully synthesized on poly-alumina substrates via a modified sol,gel method, with inorganic salt of La(NO3)3·6H2O, (NH4)6Mo7O24·4H2O, and (NH4)6H2W12O24 as precursors. Pure La2Mo2O9 phase was confirmed by X-ray diffractometer when the annealing temperature was >500°C. The average grain size of the La2Mo2,xWxO9 films is in the range of 90,400 nm, depending upon the conditions of thermal treatment, and the thickness of films can reach 1 ,m by repetitive spin-coating. The electrical conductivity increases with decreasing grain size and reaches 0.074 S/cm at 600°C in the film with a grain size of 90 nm, which is one order of magnitude higher than that in the corresponding bulk materials. W-doping can suppress the phase transition that occurs at 580°C in pure La2Mo2O9 and enhance the low-temperature ionic conductivity. Furthermore, the activation energy of conductivity in the nanocrystalline La2Mo2O9 films decreases to about 0.6 eV in comparison with 1.0 eV in the bulk ones, which implies that the grain resistance prevails in the total resistance, when grain size reduces to nanometer domain. [source] MgTiO3 and Ba0.60Sr0.40Mg0.15Ti0.85O3 Composite Thin Films with Promising Dielectric Properties for Tunable ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Lina Gao Mg2TiO4 -doped Ba0.60Sr0.40Mg0.15Ti0.85O3 (BSTM) thin films with different Mg2TiO4 concentrations were deposited on a polycrystalline alumina substrate via the sol,gel method. With the addition of Mg2TiO4, MgTiO3, MgAl2O4, and BSTM phases were formed in these composite thin films. The dielectric loss of the composite thin films decreased about one order of magnitude and the tunability still remained above 15% at a DC-applied electric field of 80 kV/cm. The dielectric constant decreased from 1040 to 388. The low dielectric constant, high tunability, and figure of merit of these composite thin films can be useful for potential tunable devices. [source] Synthesis and Characterization of Magnetic NanocontainersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008Christos Tapeinos Magnetic hollow spheres were synthesized through a two-step process and were evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy, super quantum interference device, vibrating sample magnetometry and Mössbauer spectroscopy methods. First, polystyrene spheres (PS) were produced using emulsion polymerization. Second, the PS spheres were coated via the sol,gel method to form an iron oxide layer. The size of the PS spheres was controlled by the concentration of the monomer (styrene), the initiator (potassium persulfate), and the emulsifier (sodium dodecylsulfate). The sol,gel coatings were prepared by controlled hydrolysis of aqueous solutions of FeCl3 in the presence of PS latex, polyvinylpyrrolidone, and hydrochloric acid. The composite was treated in air to burn off the PS latex. Temperature treatments were optimized after extensive differential thermal analysis and thermo gravimetric analysis characterization of the samples. Treatments under hydrogen atmosphere at various temperatures gave control over the formation and extend of magnetic phases in the nanocontainers such as a Fe, hematite (Fe2O3), and magnetite (Fe3O4). The size of the containers ranged between 300 and 400 nm. [source] Orientation Control in Sol,Gel-Derived BiScO3,PbTiO3 Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007Hai Wen BiScO3,PbTiO3 (BSPT) thin films were fabricated via a sol,gel method on Pt(111)/Ti/SiO2/Si(111) substrates. The effects of different factors on the orientation of the sol,gel-derived BSPT thin films were investigated. The results showed that a higher lead excess concentration, longer drying time, higher pyrolysis temperature, longer pyrolysis time, higher crystallization temperature, and longer crystallization time could enhance the (100) orientation of the BSPT thin films. Based on the experimental results, a mechanism for the orientation evolution in the sol,gel-derived BSPT thin films was proposed. The production of the (100) orientation was attributed to the (100)-oriented PbO nanocrystals forming during the pyrolysis process due to the lattice match. [source] Properties of Compositionally Graded BiScO3,PbTiO3 Thin Films Fabricated by a Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Hai Wen The compositionally graded BiScO3,PbTiO3 (BSPT) thin films were fabricated on Pt/Ti/SiO2/Si by a sol,gel method. For the up-graded thin film, the PbTiO3 content increased from the film,substrate interface to the surface of the film, while the down-grade thin film showed the opposite trend. The graded thin films exhibited single-phase structures and dense microstructures. The dielectric and ferroelectric properties of the thin films were investigated. The results showed that the compositionally graded BSPT thin films had similar remanent polarization value but a higher dielectric constant, dielectric tunability, and piezoelectric coefficient d33 compared with the homogeneous thin film with a composition of 0.36BiScO3,0.64PbTiO3 at the morphotropic phase boundary. [source] Synthesis of Bismuth Sodium Titanate Nanosized Powders by Solution/Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Chang Yeoul Kim (Bi1/2Na1/2)TiO3 (BNT) is a prominent candidate for a lead-free piezoelectric material. In this study, BNT was synthesized using the solution/sol,gel method, in which a solution of Bi2O3 and Na2CO3 was dissolved in HNO3 as starting materials. The solution then was mixed with ethylene glycol and titanium tetraisopropoxide. The obtained BNT powder was analyzed using FT-IR, DTA-TG, Raman spectroscopy, and high-temperature XRD. Results showed that BNT crystallization occurred above 600°C. TEM investigation showed that 100,200 nm BNT particles were formed by heat-treating the sol,gel-derived BNT sol at 700°C for 6 h. [source] Yttrium Silicate Powders Produced by the Sol,Gel Method, Structural and Thermal CharacterizationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Damien Boyer Yttrium silicate (Y2SiO5) powders of high purity have been synthesized using the sol,gel method. Alkoxide precursors were used with commercial tetraethyl orthosilicate as the silica source and yttrium propoxide synthesized from YCl3. Powders calcined from the xerogel showed submicrometer crystal sizes. These powders were sintered at temperatures <1300°C and are suitable for coating applications such as a thermal barrier system for SiC/SiC composites. [source] Transparent Anatase Nanocomposite Films by the Sol,Gel Process at Low TemperaturesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2000Atsunori Matsuda We have successfully prepared transparent anatase nanocomposite films on various types of substrates, including organic polymers, using the sol,gel method at temperatures <100°C under ambient pressure. This novel process is based on the findings that (i) anatase nanocrystals are uniquely formed in sol,gel-derived SiO2,TiO2 films that have been subjected to a hot-water treatment, and (ii) the addition of an organic polymer such as poly(ethylene glycol) in the films accelerates the formation of anatase nanocrystals. The film coating on the substrates is a promising candidate for use as a photocatalyst to decompose environmental pollutants and harmful microorganisms. [source] Preparation of ZnO thin film by the sol,gel method using low temperature ozone oxidationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010Takashi Ehara Abstract Zinc oxide thin films have been prepared by the sol,gel method from a 2-methoxyethanol solution of zinc acetate dihydrate on SiO2 substrates using air, pure oxygen, and 1% ozone in oxygen as oxygen source. In the cases where air or oxygen was used as the oxygen source for thermal annealing, samples annealed at 600 to 800,°C exhibit a (0002) peak in X-ray diffraction (XRD). A sample annealed at 700,°C exhibited the highest (0002) peak intensity in conventional thermal annealing. However, the case using 1% ozone in oxygen as the atmosphere presented different results. A sample treated in 1% ozone at 100,°C had peak intensity in XRD (0002) comparable with samples annealed at several hundreds of degree in air or oxygen. This result indicates that the high oxidation efficiency of ozone is useful in decreasing the processing temperature of the sol,gel method. [source] | |||||||||||||||||||||||||||||||