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Gel Process (gel + process)
Selected AbstractsLarge-Scale Synthesis of Water Dispersible Ceria Nanocrystals by a Simple Sol,Gel Process and Their Use as a Chemical Mechanical Planarization SlurryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2008Taekyung Yu Abstract Ceria nanocrystals with a cube shape were synthesized from the hydrolytic sol,gel reaction of cerium salt in the presence of oleylamine. The overall synthetic process is very simple and readily applicable to the large-scale synthesis of tens of grams of product in a single reaction in air. These ceria nanocrystals are readily dispersible in aqueous media without the addition of any extra dispersing agent. The aqueous dispersion of the ceria nanocrystals was successfully used as a chemical mechanical polishing slurry, and it exhibited high removal selectivity between silicon oxide and silicon nitride at pH 7.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Anatase and Rutile TiO2 Macrocellular Foams: Air,Liquid Foaming Sol,Gel Process Towards Controlling Cell Sizes, Morphologies, and Topologies,ADVANCED MATERIALS, Issue 1 2005F. Carn Titania foams (see Figure) can be produced using a non-static air,liquid foaming sol,gel process where nitrogen is bubbled through a mixture of a surfactant and a sol,gel precursor. Either anatase or rutile phase mesoporous titania foams are produced upon thermal treatment. Macroscopic cell morphologies can be tuned by changing the air-to-liquid-foam ratios and the size of the nitrogen bubbles, while wall topologies can be varied by changing surfactant. [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] Thermal Softening Behavior and Application to Transparent Thick Films of Poly(benzylsilsesquioxane) Particles Prepared by the Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Atsunori Matsuda Thick films of poly(benzylsilsesquioxane) (BnSiO3/2) particles, prepared by the sol,gel process, were deposited onto indium-tin-oxide-coated glass substrates by electrophoresis for the application to the micropatterning of the films. BnSiO3/2 particles were thermally softened and sintered at ,50°C, which was above the glass transition temperature of the particles. The films prepared by the electrophoretic sol,gel deposition consisted of aggregates of particles with diameters of 0.2,1 ,m and were opaque. The film shrank from 2.5 ,m to 1.4 ,m in thickness and became transparent upon sintering of the particles during heat treatment at temperatures >100°C. [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] ChemInform Abstract: Insulating Ultrathin Silica Films Formed by a Room-Temperature Sol,Gel Process.CHEMINFORM, Issue 34 2001Joseph W. Robertson Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of Organosilica Films Through Consecutive Sol/Gel Process and Cationic PhotopolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2010Davy-Louis Versace Abstract The cationic photopolymerization of epoxy polysilsesquioxane resins synthesized through a acid-catalyzed sol/gel process is studied. To elucidate the effect of the organic substituent on sol/gel reaction kinetics, two organotrimethoxysilanes with different organic groups were employed. Effects of UV irradiation on the microstructure of the epoxy-functional polysilsesquioxanes were also studied. 29Si solid-state MAS NMR proved that UV-generated Brönsted acids favored a work-up of the silicate network by promoting new sol/gel condensation reactions. There was a significant slowdown of epoxy conversion rates with increasing sol aging, which may be due to a competition between an active chain end and an activated monomer mechanism for the epoxy cationic polymerization. [source] Electrochemically-Induced Deposition of Amine-Functionalized Silica Films on Gold Electrodes and Application to Cu(II) Detection in (Hydro)Alcoholic MediumELECTROANALYSIS, Issue 19 2005Alain Walcarius Abstract Well-adherent amine-functionalized porous silica films have been deposited on gold electrodes by combining the self-assembly technology, the sol,gel process, and the electrochemical modulation of pH at the electrode/solution interface. A partial self-assembled monolayer of mercaptopropyl-trimethoxysilane (MPTMS) was first formed on disposable gold electrodes from recordable CDs (Au-CDtrodes). The so pretreated MPTMS-Au-CDtrodes were immersed in a stable sol solution (pH,3) containing (3-aminopropyl)-triethoxysilane (APTES) and tetraethoxysilane (TEOS). Polycondensation of the APTES and TEOS precursors was then achieved by applying a negative potential for a given period of time to generate a local pH increase at the electrode/solution interface and promote the deposition of the amine functionalized silica film adhering well to the electrode surface owing to the MPTMS monolayer acting somewhat as a "molecular glue". Various parameters affecting the electrodeposition process have been studied and the film permeability to redox probes in solution was characterized by cyclic voltammetry. The amine-functionalized silica film electrodes were then applied to the preconcentration of copper(II) species prior to their electrochemical detection by anodic stripping differential pulse voltammetry. Getting high sensitivity has however required the application of an electrochemical pre-activation step as the majority of the organo-functional groups were in the form of ammonium moieties (because the film was prepared from an acidic sol). This was achieved by applying a sufficiently negative potential to the electrode surface to reduce protons and increase consequently the amine-to-ammonium ratio within the film and, thus, the efficiency of the precocentration process. The resulting device was then optimized for copper(II) determination in hydroalcoholic medium, giving rise to a linear response in the 0.1,10,,M concentration range. [source] Hybrid silica monolithic column for capillary electrochromatography with enhanced cathodic electroosmotic flowELECTROPHORESIS, Issue 21 2006Jiwei Hu Abstract A hybrid silica monolithic stationary phase for RP CEC was prepared by in,situ co-condensation of (3-mercaptopropyl)-trimethoxysilane (MPTMS), phenyltriethoxysilane (PTES), and tetraethoxysilane (TEOS) via a sol,gel process. The thiol groups on the surface of the stationary phase were oxidized to sulfonic acids by peroxytrifluoroacetic acid. The introduced sulfonic acid moieties on the monoliths were characterized by a strong and relatively stable EOF in a broad pH range from 2.35 to 7.0 in CEC. Aromatic acids and neutral compounds can be simultaneously separated in this column under cathodic EOF. The CEC column exhibited a typical RP chromatographic mechanism for neutral compounds due to the introduced phenyl groups. [source] Assembly and Formation of Biomorphic Tin Dioxide by a Biomimetic Sol,Gel Approach Involving GlycoproteinEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Qun Dong Abstract Three diverse layers of eggshell membrane (ESM) were introduced in a biogenic sol,gel technique for the synthesis of hierarchical SnO2 nanomaterials with corresponding configurations. Typically, the biomorphic replication of the interwoven inner eggshell membrane was systematically investigated by controlling synthesis conditions such as pH value, dipping time, and calcination temperature. The as-prepared SnO2 tubes consisting of interconnected 5-nm nanocrystallite units were successfully interwoven into ESM-morphic films. Herein, the biomaterial ESM served both as the physical substrate and the functional macromolecule template to realize the precision replication, by the interactions between ESM macromolecules (containing carboxyl, hydroxy, amino groups, etc.) and Sn colloid ingredients. Moreover, some biomacromolecules also acted as the surfactant to yield small-scaled and well-distributed SnO2 nanocrystallites based on the strong bondage of short-chained amino acids within ESM glycoprotein with SnO2 nuclei. This technique can be attributed to a biomimetic sol,gel process and is widely applicable to the synthesis of other functional material systems. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Silica Supported Submicron SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ Spherical Particles with a Core,Shell Structure: Sol,Gel Synthesis and CharacterizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Cuikun Lin Abstract X1 -Y2SiO5:Eu3+ and X1 -Y2SiO5:Ce3+ and/or Tb3+ phosphor layers have been coated on nonaggregated, monodisperse, submicron spherical SiO2 particles by a sol,gel process, followed by surface reaction at high temperature (1000 °C), to give core/shell structured SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), TEM, photoluminescence (PL), low voltage cathodoluminescence (CL), and time-resolved PL spectra and lifetimes are used to characterize these materials. The XRD results indicate that X1 -Y2SiO5 layers have been successfully coated on the surface of SiO2 particles, as further verified by the FESEM and TEM images. The PL and CL studies suggest that SiO2@Y2SiO5:Eu3+, SiO2@Y2SiO5:Tb3+ (or Ce3+/Tb3+), and SiO2@Y2SiO5:Ce3+ core/shell particles exhibit red (Eu3+, 613 nm: 5D0,7F2), green (Tb3+, 542 nm: 5D4,7F5), or blue (Ce3+, 450 nm: 5d-4f) luminescence, respectively. PL excitation, emission, and time-resolved spectra demonstrate that there is an energy transfer from Ce3+ to Tb3+ in the SiO2@Y2SiO5:Ce3+,Tb3+ core/shell particles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Sol,Gel Coatings as Active Barriers to Protect Ceramic Reinforcement in Aluminum Matrix Composites,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2004J. Rams Silica obtained through a sol,gel process is used as a coating for ceramic reinforcements (SiC) in aluminium matrix composite materials. The interaction between molten aluminium and the coated particles during material casting can be controlled by means of the thermal treatment given to the coating. Wettability is increased because the coating reacts with molten aluminium, and the formation of the degrading aluminium carbide is inhibited. [source] Synthesis of Magnetic, Up-Conversion Luminescent, and Mesoporous Core,Shell-Structured Nanocomposites as Drug CarriersADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Shili Gai Abstract The synthesis (by a facile two-step sol,gel process), characterization, and application in controlled drug release is reported for monodisperse core,shell-structured Fe3O4@nSiO2@mSiO2@NaYF4: Yb3+, Er3+/Tm3+ nanocomposites with mesoporous, up-conversion luminescent, and magnetic properties. The nanocomposites show typical ordered mesoporous characteristics and a monodisperse spherical morphology with narrow size distribution (around 80,nm). In addition, they exhibit high magnetization (38.0,emu g,1, thus it is possible for drug targeting under a foreign magnetic field) and unique up-conversion emission (green for Yb3+/Er3+ and blue for Yb3+/Tm3+) under 980,nm laser excitation even after loading with drug molecules. Drug release tests suggest that the multifunctional nanocomposites have a controlled drug release property. Interestingly, the up-conversion emission intensity of the multifunctional carrier increases with the released amount of model drug, thus allowing the release process to be monitored and tracked by the change of photoluminescence intensity. This composite can act as a multifunctional drug carrier system, which can realize the targeting and monitoring of drugs simultaneously. [source] Doping of the Metal Oxide Nanostructure and its Influence in Organic ElectronicsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Mi-Hyae Park Abstract Synthesizing metal oxides through the sol,gel process provides a convenient way for forming a nanostructured layer in wide band gap semiconductors. In this paper, a unique method of introducing dopants into the metal oxide semiconductor is presented. The doped TiO2 is prepared by adding a Cs2CO3 solution to a nanocrystalline TiO2 solution that is synthesized via a non-hydrolytic sol,gel process. The properties of the TiO2:Cs layer are investigated and the results show stable nanostructure morphology. In addition to providing morphological stability, Cs in TiO2 also gives rise to a more desirable work function for charge transport in organic electronics. Polymer solar cells based on the poly(3-hexylthiophene) (P3HT): methanofullerene (PC70BM) system with the addition of a TiO2:Cs interfacial layer exhibit excellent characteristics with a power conversion efficiency of up to 4.2%. The improved device performance is attributed to an improved polymer/metal contact, more efficient electron extraction, and better hole blocking properties. The effectiveness of this unique functionality also extends to polymer light emitting devices, where a lower driving voltage, improved efficiency, and extended lifetime are demonstrated. [source] Preparation of Functional Hybrid Glass Material from Platinum (II) Complexes for Broadband Nonlinear Absorption of LightADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Roman Zieba Abstract The synthesis of trans -di(arylalkynyl)diphosphine platinum(II) complexes bearing trialkoxysilane groups is described, as well as the preparation of siloxane-based hybrid materials from organometallic chromophores through a modified sol,gel process. Glass materials prepared from trans -[P(n,Bu)3]2Pt[(C,C,p,C6H4,C,C,p,C6H4,CH2O(CO)NH(CH2)3Si(OC2H5)3]2 generally show spectral transmittance, absorption and luminescence similar to that of solutions reported in the literature. Measurements of optical power limiting for the hybrid glass are carried out, and show broadband nonlinear absorption throughout the whole visible wavelength range with clamping values in the range 0.2,7,µJ at 120,mM chromophore concentration. The sol,gel process using urethane-propyltriethoxysilane-functionalized chromophores as precursors appears to be a valid method for formation of robust silicate materials with grafted diarylethynyl Pt(II) complexes for OPL devices. [source] A Facile Synthesis and Characterization of Monodisperse Spherical Pigment Particles with a Core/Shell Structure,ADVANCED FUNCTIONAL MATERIALS, Issue 9 2007C. Lin Abstract In this paper, a facile sol,gel process for producing monodisperse, spherical, and nonaggregated pigment particles with a core/shell structure is reported. Spherical silica particles (245 and 385,nm in diameter) and Cr2O3, ,-Fe2O3, ZnCo2O4, CuFeCrO4, MgFe2O4, and CoAl2O4 pigments are selected as cores and shells, respectively. The obtained core/shell-structured pigment samples, denoted as SiO2@Cr2O3 (green), SiO2@,-Fe2O3 (red), SiO2@MgFe2O4 (brown), SiO2@ZnCo2O4 (dark green), SiO2@CoAl2O4 (blue), and SiO2@CuFeCrO4 (black), are well characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and UV-vis diffuse reflection, as well as by investigating the magnetic properties. The results of XRD and high-resolution TEM (HRTEM) demonstrate that the pigment shells crystallize well on the surface of SiO2 particles. The thickness of the pigment shell can be tuned by the number of coatings, to some extent. These pigment particles can be well dispersed in some solvents (such as glycol) to form relatively more stable suspensions than the commercial products. Apart from the color characteristics, some of pigments like SiO2@Cr2O3, SiO2@MgFe2O4, and SiO2@CuFeCrO4 also show magnetic properties with coercivities of 1098,Oe (5,K), 648,Oe (5,K), and 91,Oe (298,K), respectively. [source] A New Sol,Gel Material Doped with an Erbium Complex and Its Potential Optical-Amplification Application,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2005L.-N. Sun Abstract The crystal structure of a ternary Er(DBM)3phen complex (DBM,=,dibenzoylmethane; phen,=,1,10-phenanthroline) and its in-situ synthesis via a sol,gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er3+/DBM/phen co-doped luminescent hybrid gel, formed via an in-situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near-IR luminescence (centered at around 1.54,,m) resulting from the 4I13/2,,,4I15/2 transition of the Er3+ ion, which contributes to the efficient energy transfer from the ligands to the Er3+ ion in both the Er(DBM)3phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541,nm in the emission spectrum of the ErDP gel is 72,nm, which has potential for optical-amplification applications. Further theoretical analysis on the Er3+ ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers. [source] Highly Non-Linear Quantum Dot Doped Nanocomposites for Functional Three-Dimensional Structures Generated by Two-Photon PolymerizationADVANCED MATERIALS, Issue 22 2010Baohua Jia A nanocomposite consisting of a photosensitive organic,inorganic hybrid polymer functionalized with PbS quantum dots has been developed using a sol,gel process. The uniformly dispersed nanocomposite exhibits ultrahigh third-order non-linearity (,3.2,×,10,12 cm2 W,1) because of the strong quantum confinement of small-sized and narrowly distributed quantum dots. The non-linear nanocomposite has been proven to be suitable for the fabrication of 3D micro/nano photonic devices using two-photon polymerization. The fabricated photonic crystals show stop gaps with more than 60% suppression in transmission at the telecommunications wavelength region. [source] Anatase and Rutile TiO2 Macrocellular Foams: Air,Liquid Foaming Sol,Gel Process Towards Controlling Cell Sizes, Morphologies, and Topologies,ADVANCED MATERIALS, Issue 1 2005F. Carn Titania foams (see Figure) can be produced using a non-static air,liquid foaming sol,gel process where nitrogen is bubbled through a mixture of a surfactant and a sol,gel precursor. Either anatase or rutile phase mesoporous titania foams are produced upon thermal treatment. Macroscopic cell morphologies can be tuned by changing the air-to-liquid-foam ratios and the size of the nitrogen bubbles, while wall topologies can be varied by changing surfactant. [source] Epoxy,siloxane hybrid coatings by a dual-curing processADVANCES IN POLYMER TECHNOLOGY, Issue 2 2009Giulio Malucelli Abstract Coatings based on a hybrid organic,inorganic epoxy system were prepared by a dual-curing mechanism, via cationic photopolymerization in the first step at room temperature and a subsequent hydrolysis/condensation reaction of a trialkoxy-silane compound (sol,gel process) at high temperature. To this end, a high Tg epoxy resin (3,4-epoxycyclohexylmethyl-3,-cyclohexenyl-methyl adipate, UVR 6128) was added in increasing amounts to a precursor for the inorganic-like phase (3,4-epoxycyclohexylethyltrimethoxysilane, EETMOS). The mixture contained triphenylsulfoniumhexafluoroantimonate as a cationic photoinitiator. By this method, the strongly acid environment generated by the photolysis of the triarylsolfunium salt in the first step induces the hydrolysis of EETMOS alkoxy-silane groups. The films produced in the first step of the process were thermal treated to promote the condensation reactions of the siloxane moieties. The kinetics of the reactions of photopolymerization and condensation was investigated. It was found that the presence of EETMOS increases both the polymerization rate and the final consumption of epoxy groups. Thermogravimetric analyses performed in air have revealed an increased stability of the hybrid coatings with respect to the films produced from formulations without EETMOS. A significant increase in surface hardness was also observed for the hybrid coatings. The thermo-mechanical properties were found to be strongly affected by the temperature used in the thermally induced reactions in the second step. The hybrid coatings on a low-density polyethylene substrate were found to decrease the diffusivity of oxygen and to increase the oxygen solubility within the coating. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:77,85, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20149 [source] Structure of magnetic poly(oxyethylene),siloxane nanohybrids doped with FeII and FeIIIJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2003N. J. O. Silva Hybrid organic,inorganic nanocomposites doped with FeII and FeIII ions and exhibiting interesting magnetic properties have been obtained by the sol,gel process. The hybrid matrix of these ormosils (organically modified silicates), classed as di-ureasils and termed U(2000), is composed of poly(oxyethylene) chains of variable length grafted to siloxane groups by means of urea crosslinkages. Iron perchlorate and iron nitrate were incorporated in the di-ureasil matrices, leading to compositions within the range 80 ,n, 10, n being the molar ratio of ether-type O atoms per cation. The structure of the doped di-ureasils was investigated by small-angle X-ray scattering (SAXS). For FeII -doped samples, SAXS results suggest the existence of a two-level hierarchical structure. The primary level is composed of spatially correlated siloxane clusters embedded in the polymeric matrix and the secondary, coarser level consists of domains where the siloxane clusters are segregated. The structure of FeIII -doped hybrids is different, revealing the existence of iron oxide based nanoclusters, identified as ferrihydrite by wide-angle X-ray diffraction, dispersed in the hybrid matrix. The magnetic susceptibility of these materials was determined by zero-field-cooling and field-cooling procedures as functions of both temperature and field. The different magnetic features between FeII - and FeIII -doped samples are consistent with the structural differences revealed by SAXS. While FeII -doped composites exhibit a paramagnetic Curie-type behaviour, hybrids containing FeIII ions show thermal and field irreversibilities. [source] Micellar behavior of well-defined polystyrene-based block copolymers with triethoxysilyl reactive groups and their hydrolysis,condensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010Cé Guinto Gamys Abstract Block copolymers of acryloxy propyl triethoxysilane and styrene were prepared through nitroxide-mediated polymerization using alkoxyamine initiators based on N - tert -butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide. The copolymers were characterized by 1H NMR, size exclusion chromatography and differential scanning calorimetry. Their micellar behavior in dioxane/methanol solutions was examined through static light scattering and transmission electron microscopy (TEM). TEM indicated the successful formation of spherical micelles which were subsequently frozen by the sol,gel process. Hydrolysis,condensation of the reactive ethoxysilyl side groups was followed by FTIR, 1H NMR, and 29Si NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 784,793, 2010 [source] Water-resistant conducting hybrids from electrostatic interactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007Jing Luo Abstract Conductive hybrids were prepared in a water/ethanol solution via the sol,gel process from an inorganic sol containing carboxyl groups and water-borne conductive polyaniline (cPANI). The inorganic sol was prepared by the hydrolysis and condensation of methyltriethoxysilane with the condensed product of maleic anhydride and aminopropyltriethoxysilane as a catalyst, for which the carboxyl counterion along the cPANI backbone acted as an electrostatic-interaction moiety. The existence of this electrostatic interaction could improve the compatibility of the two components and contribute to the homogeneous dispersion of cPANI in the silica phase. The electrostatic-interaction hybrids displayed a conductivity percolation threshold as low as 1.1 wt % polyaniline in an emeraldine base, showing 2 orders of magnitude higher electrical conductivity than that without electrostatic interactions. The electrostatic-interaction hybrids also showed good water resistance; the electrical conductivity with a cPANI loading of 16 wt % underwent a slight change after 14 days of soaking in water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1424,1431, 2007 [source] Proton transportation in an organic,inorganic hybrid polymer electrolyte based on a polysiloxane/poly(allylamine) networkJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2005Ping-Lin Kuo Abstract A new class of proton-conducting polymer was developed via the sol,gel process from amino-containing organic,inorganic hybrids by the treatment of poly(allylamine) with 3-glycidoxypropyltrimethoxysilane doped with ortho -phosphoric acid. The polymer matrix contains many hydrophilic sites and consists of a double-crosslinked framework of polysiloxane and amine/epoxide. Differential scanning calorimetry results suggest that hydrogen bonding or electrostatic forces are present between H3PO4 and the amine nitrogen, resulting in an increase in the glass-transition temperature of the poly(allylamine) chain with an increasing P/N ratio. The 31P magic-angle spinning NMR spectra indicate that three types of phosphate species are involved in the proton conduction, and the motional freedom of H3PO4 is increased with increasing P/N ratios. The conductivity above 80 °C does not drop off but increases instead. Under a dry atmosphere, a high conductivity of 10,3 S/cm at temperatures up to 130 °C has been achieved. The maximum activation energy obtained at P/N = 0.5 suggests that a transition of proton-conducting behavior exits between Grotthus- and vehicle-type mechanisms. The dependence of conductivity on relative humidity (RH) above 50% is smaller for H3PO4 -doped membranes compared with H3PO4 -free ones. These hybrid polymers have characteristics of low water content (23 wt %) and high conductivity (10,2 S/cm at 95% RH), making them promising candidates as electrolytes for fuel cells. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3359,3367, 2005 [source] Synthesis and properties of silica/polystyrene/polyaniline conductive composite particlesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Chia-Fen Lee Abstract In this study, silica/polystyrene/polyaniline (SiO2/PS/PANI) conductive composite particles were synthesized by four sequential reactions. The nanosized SiO2 particles were synthesized from tetraethoxysilane (TEOS) by a sol,gel process with water as the solvent medium, followed by a surface modification with triethoxyvinylsilane; then the surface modified SiO2 particles were used as seeds to synthesize SiO2/PS composite particles with soapless seeded emulsion polymerization. Finally, the SiO2/PS particles were used as seeds to synthesize the SiO2/PS/PANI conductive composite particles. The sol,gel process of SiO2, the effect of surface modification, and several other factors that influenced polymerization of styrene in the soapless seeded emulsion polymerization will be discussed. Either potassium persulfate (KPS) or 2,2,-azobis(isobutyramidine) dihydrochloride (AIBA) was used as the initiator to synthesize the uniform SiO2/PS particles successfully, and the cross-section morphology of the SiO2/PS particles was found to be of a core,shell structure, with SiO2 as the core, and PS as the shell. The SiO2/PS particles were well dispersed in many organic solvents. In the following step to synthesize SiO2/PS/PANI conductive composite particles, sodium dodecyl sulfate (SDS) played an important role, specifically, to absorb aniline onto the surfaces of the SiO2/PS particles to carry out the polymerization of aniline over the entire surface of the particles. The conductivity of the SiO2/PS/PANI composite particles approached that of semiconductive materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 342,354, 2005 [source] Syntheses and characterizations of bis(trialkoxysilyl)oligoimides.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2001Abstract Novel crosslinkable fluorinated oligoimides were prepared in two steps. The first involved the synthesis of oligoimides terminated with nadic or allylic double bonds, and the second step was materialized either by a radical addition of mercaptotrialkoxysilane derivatives onto nadic double bonds or a hydrosilylation reaction of hydrogenotrialkoxysilane derivative onto allylic double bonds. Three kinds of crosslinking of the trialkoxysilane end groups were studied. The first kind entailed a thermal self-crosslinking of trialkoxysilane groups. The second process of crosslinking incorporated a bicomponent system,the crosslinked agent was 1,1,1-tris(4-hydroxyphenyl)ethane (TRIOH). The trialkoxysilane groups reacted with the hydroxyl,phenol groups of TRIOH to give thermally stable phenoxysilane bonds as well as a crosslinking network. The last method was also a bicomponent system; the oxalic acid was added into an oligoimide solution where by thermal treatment water was created. The water molecules hydrolyzed the trialkoxysilane groups into silanol groups that polycondensed into a crosslinked network following a sol,gel process. The mechanism of the different crosslinking reactions was investigated by Fourier transform infrared spectroscopy and solid-state 29Si NMR. The self-crosslinked material prepared from precursor ,,,-trimethoxysilyl fluorinated oligomer (Mn = 5500 g · mol,1) exhibited a 10 wt % loss temperature under air higher than 420 °C and a low birefringence (,n = 0.008) at 1.300 ,m. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2602,2619, 2001 [source] Multiferroic Properties of Nanocrystalline PbTiO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Min Wang Nanocrystalline PbTiO3 (PTO) powders in a perovskite structure have been synthesized by the sol,gel process using lead acetate, glycerin, and titanium (IV) isopropoxide as precursors. PTO ceramics were obtained by sintering the powders at temperatures ranging from 600° to 1000°C. The structure and morphology of the ceramics have been determined by X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy. The PTO powder calcined at 450°C shows weak ferromagnetism at room temperature. The PTO ceramics sintered at various temperatures exhibit coexistence of ferroelectricity and weak ferromagnetism at room temperature. Enhancement in the magnetic moment and ferroelectricity with a reduction in the grain size of PTO ceramics was observed. This result facilitates the possibilities of new perovskite electromagnetic devices at the nanoscale level. [source] Monolithic Ceramic Foams for Ultrafast Photocatalytic Inactivation of BacteriaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Pinggui Wu Palladium-modified nitrogen-doped titanium dioxide (TiON/PdO) foams were synthesized by a sol,gel process on a polyurethane foam template. The TiON/PdO foam was tested for microbial killing using Escherichia coli cells as a target. Under visible-light illumination, the TiON/PdO foam displayed a strong antimicrobial effect on the bacteria cells in water. The antimicrobial effect was found to be dependent on the palladium content and the calcination temperature. In a flow-through dynamic photoreactor, the new photocatalyst efficiently inactivated E. coli within a short contact time (<1 min), the shortest ever reported for the photocatalytic killing of bacteria. The strong antimicrobial functions of the TiON/PdO foam were related to charge trapping by PdO and the high contact efficiency of the foam structure. [source] Dielectric Tunable Properties and Relaxor Behavior of (Pb0.5Ba0.5)ZrO3 Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008Xihong Hao Pb0.5Ba0.5ZrO3 (PBZ50) thin films with a thickness of about 500 nm in the paraelectric-phase were deposited on Pt/Ti/SiO2/Si substrates via the sol,gel process. The room-temperature dielectric measurements showed that the tunability and figure of merit (FOM) of the PBZ50 films at the maximum external DC field of 200 kV/cm were 39% and 38%, respectively. The results of temperature-dependent dielectric measurements confirmed that PBZ50 films had a typical diffuse phase transition characteristic and relaxor behavior. [source] | |||||||||||||||||||||||||||||||