Home About us Contact
|
Home About us Contact | ||
|
|
||
Gel Route (gel + route)
Selected AbstractsPreparation of NiAl2O4/SiO2 and Co2+ -Doped NiAl2O4/SiO2 Nanocomposites by the Sol,Gel RouteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006I. Prakash NiAl2O4/SiO2 and Co2+ -doped NiAl2O4/SiO2 nanocomposite materials of compositions 5% NiO , 6% Al2O3, 89% SiO2 and 0.2% CoO , 4.8% NiO , 6% Al2O3, 89% SiO2, respectively, were prepared by a sol,gel process. NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals were grown in a SiO2 amorphous matrix at around 1073 K by heating the dried gels from 333 to 1173 K at the rate of 1 K/min. The formations of NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals in SiO2 amorphous matrix were confirmed through X-ray powder diffraction, Fourier transform infrared spectroscopy, differential scanning calorimeter, transmission electron microscopy (TEM), and optical absorption spectroscopy techniques. The TEM images revealed the uniform distribution of NiAl2O4 and cobalt-doped NiAl2O4 nanocrystals in the amorphous SiO2 matrix and the size was found to be ,5,8 nm. [source] Synthesis of Ba(Mg1/3Ta2/3)O3 Microwave Ceramics through a Sol,Gel Route Using Acetate SaltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004Chien-Cheng Tsai A sol,gel process to unsophisticatedly synthesize Ba(Mg1/3Ta2/3)O3 (BMT) ceramics at low cost has been developed in the present work. This process involves the reaction of TaCl5 with acetates of Ba and Mg in the presence of citric acid. Pure BMT polycrystalline powders can be obtained by calcining the synthesized products at 1000°C. The BMT powders were found to have a primary particle size as small as 100 nm. BMT ceramics with favorable structural characteristics can be obtained from sintering of the sol,gel BMT at temperatures much lower than that for the conventional solid-state BMT. Sintering the sol,gel BMT in pellet form at 1300°C resulted in an ordering parameter of 0.72 for the pellet, and a relative density of >95% was achieved with sintering at 1500°C. The grain size of the sintered sol,gel BMT was large and uniform in comparison with the products from the solid-state method. Using the sol,gel route, sintering at temperatures as low as 1400°C gave ceramics with acceptable microwave dielectric properties (a dielectric constant of 16 and Qf factor of 14 400 GHz), while higher temperatures (>1600°C) are needed for the solid-state route to give similar properties. [source] Preparation of a Mesoporous Silicon Boron Nitride via a Non-aqueous Sol,Gel Route.CHEMINFORM, Issue 16 2003Fei Cheng Abstract For Abstract see ChemInform Abstract in Full Text. [source] Aqueous Lithium-ion Battery LiTi2(PO4)3/LiMn2O4 with High Power and Energy Densities as well as Superior Cycling Stability**,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007J.-Y. Luo Abstract Porous, highly crystalline Nasicon-type phase LiTi2(PO4)3 has been prepared by a novel poly(vinyl alcohol)-assisted sol,gel route and coated by a uniform and continuous nanometers-thick carbon thin film using chemical vapor deposition technology. The as-prepared LiTi2(PO4)3 exhibits excellent electrochemical performance both in organic and aqueous electrolytes, and especially shows good cycling stability in aqueous electrolytes. An aqueous lithium-ion battery consisting of a combination of LiMn2O4 cathode, LiTi2(PO4)3 anode, and a 1 M Li2SO4 electrolyte has been constructed. The cell delivers a capacity of 40 mA,h,g,1 and a specific energy of 60 W,h,kg,1 with an output voltage of 1.5 V based on the total weight of the active electrode materials. It also exhibits an excellent cycling stability with a capacity retention of 82,% over 200 charge/discharge cycles, which is much better than any aqueous lithium-ion battery reported. [source] Synthesis of high fluorescent silica hybrid materials by immobilization of orange peel extract in silica-silsesquioxane matrixJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2009I. Lacatusu Abstract Sol,gel chemistry can be easily modified to the changing needs of society to produce fine-tuned sol,gel nanostructured materials for relevant applications. In this context, there is an increasing need for natural and versatile raw materials as well as biocompatible compounds that could be extensively used as biomarkers for bioimaging in diagnosis or therapy. Silica-based materials are widely used in the field of biomedicine due to their chemical inertness and biocompatibility. In the present paper, orange peel extract was immobilized inside inorganic silica and hybrid silica-silsesquioxane polymeric networks. Silica and organo-modified silica matrices were synthesized through a templated sol,gel route of TEOS and an organosilsesquioxane (octaisobutyltetracyclo[7.3.3.15,11] octasiloxane- endo -3,7-diol), with D -glucose as template, and for comparison a non-ionic surfactant (tetraethylene glycol mono-hexadecyl ether) was also used. The bioactive properties of the molecules from orange peel extract were preserved after immobilization in both silica and silica-silsesquioxane networks. Moreover, the fluorescence properties were amplified by 10,20 times more than the native orange peel extract. The structural properties of the final materials have been studied by FT-IR, UV,Vis-NIR, and fluorescence spectroscopy. Dynamic light scattering measurements and transmission electron microscopy were used to estimate the size and morphology of the hybrid materials with orange peel extract immobilized in silica networks. Copyright © 2009 John Wiley & Sons, Ltd. [source] Electrochemical Behavior of Gel-Derived Lanthanum Calcium Cobalt Ferrite Cathode in Contact with LAMOX ElectrolyteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Tsu-Yung Jin The electrochemical performance and structural features of (La1,yCay)(CoxFe1,x)O3 cathode prepared via a citrate acid gel route are studied when it is interfaced with the (La1.8Dy0.2)(Mo2,zWz)O9 electrolyte. The resistance and chemical capacitance of a low-frequency arc are extracted from the impedance results to evaluate its catalytic activity in oxygen reduction reaction (ORR). (La0.75Ca0.25)(Co0.8Fe0.2)O3 cathode exhibits the minimum area-specific resistance of 0.9 , cm2 and maximum capacitance of 5.7 mF/cm2 at 800°C among the compositions of x=0.1,0.9 and y=0.25. As the Co content increases, the decrease in resistance outweighs the increase in capacitance so that the product of resistance and capacitance (RC time constant) decreases. In contrast, when varying the Ca content of the A-site, the changes in resistance and the capacitance compensate each other; hence the RC time constant is virtually unchanged with respect to the calcium content. Thus, Co is a more influential element than Ca on the ORR catalytic activity. The pore structure study reveals a small amount of Mo diffuses from the electrolyte into the cathode, and its quantity is reduced when interfaced to an electrolyte of high W content. [source] Preparation and Electrical Properties of an Anodized Al2O3,BaTiO3 Composite FilmJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Xianfeng Du A highly stable, water-based barium titanate BaTiO3, BT, sol was synthesized using a sol,gel route through a chelate lactate technique. Dried BT precursor powders were measured by thermal gravimetry,differential thermal analysis and X-ray diffraction. It was found that BT powders first converted into barium carbonate BaCO3, Ti complex, and intermediate phase Ba2Ti2O5CO3, and then transformed into perovskite phase BaTiO3. The crystallization temperature was about 550°C. The low-voltage etched aluminum foils were covered with BT sol by dip coating, and then annealed at 600°C for 30 min in air. After that, the samples were anodized in a 15 wt% aqueous solution of ammonium adipate. The voltage,time variations during anodizing were monitored, and the electrical properties of the anodic oxide film were examined. It was shown that the specific capacitance, the product of specific capacitance and withstanding voltage, and leakage current of samples with a BT coating were about 48.93%, 38.50%, and 167% larger than that without a BT coating, respectively. [source] Synthesis of Ba(Mg1/3Ta2/3)O3 Microwave Ceramics through a Sol,Gel Route Using Acetate SaltsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004Chien-Cheng Tsai A sol,gel process to unsophisticatedly synthesize Ba(Mg1/3Ta2/3)O3 (BMT) ceramics at low cost has been developed in the present work. This process involves the reaction of TaCl5 with acetates of Ba and Mg in the presence of citric acid. Pure BMT polycrystalline powders can be obtained by calcining the synthesized products at 1000°C. The BMT powders were found to have a primary particle size as small as 100 nm. BMT ceramics with favorable structural characteristics can be obtained from sintering of the sol,gel BMT at temperatures much lower than that for the conventional solid-state BMT. Sintering the sol,gel BMT in pellet form at 1300°C resulted in an ordering parameter of 0.72 for the pellet, and a relative density of >95% was achieved with sintering at 1500°C. The grain size of the sintered sol,gel BMT was large and uniform in comparison with the products from the solid-state method. Using the sol,gel route, sintering at temperatures as low as 1400°C gave ceramics with acceptable microwave dielectric properties (a dielectric constant of 16 and Qf factor of 14 400 GHz), while higher temperatures (>1600°C) are needed for the solid-state route to give similar properties. [source] Electrocaloric effect in antiferroelectric PbZrO3 thin filmsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2008Jayanta Parui Abstract Antiferroelectric PbZrO3 thin films have been deposited on Pt(111)/Ti/SiO2/Si substrate by polymer modified sol,gel route. Temperature dependent P ,E hysteresis loops have been measured at 51 MV/m within a temperature range of 40 °C to 330 °C. The maximum electrocaloric effect ,0.224 × 10,6 K mV,1 has been observed near the dielectric phase transition temperature (235 °C) of the thin films. The electrocaloric effect and its strong temperature dependence have been attributed to nearly first-order phase transition. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preparation and characterization of transparent PANI-SIO2 hybrid conducting filmsPOLYMER ENGINEERING & SCIENCE, Issue 5 2010Li Wei Dodecylbenzene sulfonic acid-doped polyaniline (DBSA-PANI) was prepared with 3-glycidoxypropyltrimethoxysilane (GPTMS) through a sol,gel route without water and ethanol. Acetic acid was used to play both the roles of reagent and catalyst during the hydrolysis-condensation reaction of GPTMS, which affected the structure of precursors. On the other hand, m -cresol can adjust the acidity of solution and it was also a secondary dopant in DBSA-PANI to enhance conductivity of hybrid films. The conductivity and visible light transmittance vary with the molar ratio of acetic acid to GPTMS and m -cresol to GPTMS. Sheet resistance of the new hybrid films made by a dipping process reaches 5.1 k,/, and visible light transmittance is higher than 75%. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Self-Assembling of Er2O3,TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal RouteCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Beatriz Julián-López Dr. Abstract An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3,TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O3,TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313,m2,g,1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol,gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers. [source] Indication of Local Phase Separation in Polyimide/Silica Hybrid Polymers,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Antonino Bartolotta Abstract PI/SiO2 hybrid polymers involving the in situ generation of SiO2 particles through the sol/gel route have emerged as promising materials in many fields of modern technology thanks to their unique structural characteristics. In this paper their structural and dynamic properties were investigated by FT-IR and DMTA as a function of SiO2 content. All data consistently highlight a loosening of polymeric structure due to the presence of SiO2 nanoparticles and suggest a silica-induced structural change most probably due to a sub-micrometer scale SiO2 phase separation. Our results demonstrate how the analysis of sub-glass ,-relaxation dynamics can be exploited to investigate sub-micro phase segregation in such materials. [source] | |||||||||||||