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Titania
Terms modified by Titania Selected AbstractsNanocarving of Titania as a Diffusion-Driven Morphological Instability,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2008Doh-Kwon Lee Abstract Under strongly reducing conditions at high temperatures titania develops a specific surface morphology, comprising a regular array of fibers with a diameter in the sub-micrometer range. By a chemical diffusion experiment in a defined oxygen potential gradient it is shown that this surface structuring is caused by a diffusion-driven morphological instability of an advancing reaction front (surface). The kinetics of the process is analyzed in terms of linear transport equations. The conditions for the occurrence of the surface instability are discussed and the required materials properties are analyzed. The observed surface structuring is not restricted to titania, rather it has to occur in all nonstoichiometric compounds with predominant cation mobility. [source] Design of Experiments (DOE) for the Optimization of Titania,hydroxyapatite Functionally Graded CoatingsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Valeria Cannillo Titania,hydroxyapatite functionally graded coatings were deposited on titanium alloy substrates by plasma spraying. Because it was necessary to spray together the titania and the hydroxyapatite powders to obtain the graded system, the first target of the present study was to optimize the process parameters in order to obtain a high-quality coating. A 23 Design of Experiments was applied to define the optimal values of plasma torch power, hydrogen flux, and spraying distance. This defined set of parameters (38 kW, 5 SLPM, and 90 mm, respectively) was used to spray the most promising graded coating, which was characterized and postheat treated. [source] Thermal Stability of a Chemically Vapor Deposited Multilayer Coating Containing Amorphous Silica and Rutile Titania on Hi-Nicalon FiberJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2003Jinil Lee A multilayer coating consisting of consecutive layers of amorphous-silica, rutile-titania, and amorphous-silica was prepared on Hi-Nicalon fiber by chemical vapor deposition at 1050°C. It appeared that the silica and titania layers were strongly bonded to each other with no evidence of detachment and crack deflection at the interface region. The layered structure became morphologically unstable because of the growth of titania grains, the crystallization of the silica layers, and the oxidation of the fiber on exposure to 1200°C in air for 92 h. [source] Electrostatic Stabilization of Ultrafine Titania in EthanolJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2002Johnny Widegren The colloidal stability of a suspension of very fine titania (TiO2) powder in ethanol has been investigated. The electrokinetic behavior and stability ratios were determined as a function of operational pH and salt concentration. We show that the stability is strongly dependent on ionic strength; the TiO2suspensions will aggregate relatively rapidly at ionic strengths >10,3M, while suspensions exhibiting long-term stability can be made at ,10,4M, providing that the zeta potential of the TiO2particles is sufficiently high, i.e., |,|= 40,50 mV. Theoretical estimates of the stability based on electrostatic repulsion show a relatively good correlation with the experimental results, in particular in the acidic operational pH (pH*) range. [source] Fabrication of Free-Standing Titania-Based Gas Sensors by the Oxidation of Metallic Titanium FoilsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Pelagia I. Gouma A simple method for fabricating TiO2 -based sensors of CO(g) is demonstrated: the oxidation of Ti-bearing foils. Metallic foils (35 ,m thick) were converted into free-standing, porous rutile foils (60 ,m thick) by exposure to O2(g) at 800°,965°C. The oxidized foils contained thin (0.5,1 ,m thick), regularly spaced oxide layers oriented parallel to the external surface. The exposure of such porous foils to increasing concentrations of CO(g) resulted in a monotonic increase in the steady-state electrical resistance. Rutile foils sensitive to 50 ppm changes in CO(g) content with response times of a few minutes were produced. The effects of oxidation conditions and copper doping on sensing performance are discussed. [source] Enhanced Bactericidal Activity of Modified Titania in Sunlight against Pseudomonas aeruginosa, a Water-Borne PathogenPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2010S. Swetha Photocatalyst-mediated inactivations generate reactive oxygen species and OH radicals, which induce oxidative destruction of membrane integrity, causing damage to membrane phospholipids of gram negative bacteria like Pseudomonas aeruginosa. Nanosized TiO2 was synthesized by gel to crystalline conversion and Zr-doped TiO2 was synthesized by pulverization using appropriate precursor. The doped nanocrystals retained the anatase phase with a marginal increase in crystallite size, averaging at 25 nm. SEM,EDX analysis of the doped sample depicts the substantial growth of grain size with 1.33 atomic weight % of zirconium. The created electron states in the doped sample act as charge carrier traps suppressing recombination which later detraps the same to the surface of the catalyst causing enhanced interfacial charge transfer. Zr-doped TiO2 at the molecular scale exhibits better photocatalytic activity with lower bandgap energy that can respond to visible light. The redshift caused by the dopants in absorption spectra of TiO2 facilitated the nonintrinsic sample to exhibit nearly 2-fold enhancement of photoinactivation in sunlight. Extent of photoinactivation of P. aeruginosa was observed to be complete (100%) within 150 min of sunlight exposure in the presence of modified TiO2. [source] Photodegradation of Methanol Under UV,Visible Irradiation by Titania Dispersed on Polyester ClothPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010Kaustava Bhattacharyya Titania supported on polyester fabric (TiO2,PY) with varying titania loadings (2,7 wt%) were prepared via the dip-coating method at room temperature using an aqueous slurry of anatase titania. Structural and morphological characterizations by X-ray diffraction and scanning electron microscopy revealed that the titanium dioxide crystallites deposited on the surface of the polyester fabric were in the micrometer range while their phase remained to be anatase. Photocatalytic activity of TiO2,PY fabric catalysts was evaluated for vapor-phase oxidation of methanol in air as a test reaction in the presence of UV as well as solar radiation under ambient conditions. These catalysts were found to be quite active in both UV and solar irradiation with activity being higher in the former case. CO2 yield from photo-oxidation of methanol depended on titania content and also on its dispersion over polyester fabric support. [source] Prediction of electronic, structural and elastic properties of the hardest oxide: TiO2PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009M. A. Caravaca Abstract This work combines the theory of elasticity with first principles quantum mechanic calculations to predict the electronic, structural and elastic properties: elastic constants, bulk moduli of the TiO2 (Titania) in the Pnma phase. Band-structure shows a direct gap in , which increases its value under hydrostatic pressure. It has two regimes: in the range 0,50 GPa the band-gap has a negative second pressure derivative and changes its sign in the range 50,100 GPa. The band gap becomes indirect at pressures above 150 GPa. This phase improves its mechanical stability and insulator properties under extreme conditions of hydrostatic pressures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low Temperature Growth of Photoactive Titania by Atmospheric Pressure PlasmaPLASMA PROCESSES AND POLYMERS, Issue 9 2009John L. Hodgkinson Abstract Atmospheric pressure glow discharge plasma CVD was used to deposit thin films of titania at 200,°C using two different precursors. The resulting films were characterised using techniques including XPS, RBS and XRD. It was established that annealing at temperatures as low as 275,°C produced crystalline films that were photocatalytically active. When annealed at 300,°C the photoactivity was greater than that of commercially available "self-cleaning" titania films. The effects of the different precursors, annealing times and temperatures on the crystallinity and photoactivity are discussed. [source] Towards Flexible Inorganic "Mesomaterials": One-Pot Low Temperature Synthesis of Mesostructured Nanocrystalline Titania.CHEMINFORM, Issue 39 2004Soenke Haseloh Abstract For Abstract see ChemInform Abstract in Full Text. [source] Tris(2,2,-bipyridyl)ruthenium(II) Electrogenerated Chemiluminescence Sensor Based on Platinized Carbon Nanotube,Zirconia,Nafion Composite FilmsELECTROANALYSIS, Issue 12 2010Hyun Yoon Abstract Mesoporous films of platinized carbon nanotube,zirconia,Nafion composite have been used for the immobilization of tris(2,2,-bipyridyl)ruthenium (II) (Ru(bpy)32+) on an electrode surface to yield a solid-state electrogenerated chemiluminescence (ECL) sensor. The composite films of Pt,CNT,zirconia,Nafion exhibit much larger pore diameter (3.55,nm) than that of Nafion (2.82,nm) and thus leading to much larger ECL response for tripropylamine (TPA) because of the fast diffusion of the analyte within the films. Due to the conducting and electrocatalytic features of CNTs and Pt nanoparticles, their incorporation into the zirconia,Nafion composite films resulted in the decreased electron transfer resistance within the films. The present ECL sensor based on the Pt,CNT,zirconia,Nafion gave a linear response (R2=0.999) for TPA concentration from 3.0,nM to 1.0,mM with a remarkable detection limit (S/N=3) of 1.0,nM, which is much lower compared to those obtained with the ECL sensors based on other types of sol-gel ceramic,Nafion composite films such as silica,Nafion and titania,Nafion. [source] Performance of Impedimetric Biosensors Based on Anodically Formed Ti/TiO2 ElectrodesELECTROANALYSIS, Issue 20 2005Aikaterini Abstract The advantages and limitations of impedimetric sensors based on Ti/TiO2 architectures are described. Titanium dioxide (titania) was potentiostatically formed onto titanium electrodes of 2,mm diameter, at 10 and 30,V in 1,M H2SO4. The thickness of the titania layers was ellipsometrically determined to be 30 and 86,nm respectively and they are highly insulating with charge-transfer resistances in the M, range, as they were measured with electrochemical impedance spectroscopy under specific experimental conditions. Low voltage anodization (<10,V) results to amorphous TiO2, whereas at higher applied voltages (>25,V), anatase is the predominant form. SEM images are indicative of quite smooth, compact coatings without any severe cracks. [source] Control of Solid-State Dye-Sensitized Solar Cell Performance by Block-Copolymer-Directed TiO2 SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Pablo Docampo Abstract Hybrid dye-sensitized solar cells are typically composed of mesoporous titania (TiO2), light-harvesting dyes, and organic molecular hole-transporters. Correctly matching the electronic properties of the materials is critical to ensure efficient device operation. In this study, TiO2 is synthesized in a well-defined morphological confinement that arises from the self-assembly of a diblock copolymer,poly(isoprene- b -ethylene oxide) (PI- b -PEO). The crystallization environment, tuned by the inorganic (TiO2 mass) to organic (polymer) ratio, is shown to be a decisive factor in determining the distribution of sub-bandgap electronic states and the associated electronic function in solid-state dye-sensitized solar cells. Interestingly, the tuning of the sub-bandgap states does not appear to strongly influence the charge transport and recombination in the devices. However, increasing the depth and breadth of the density of sub-bandgap states correlates well with an increase in photocurrent generation, suggesting that a high density of these sub-bandgap states is critical for efficient photo-induced electron transfer and charge separation. [source] Multilayer Hybrid Films Consisting of Alternating Graphene and Titania Nanosheets with Ultrafast Electron Transfer and Photoconversion PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Kiran Kumar Manga Abstract Alternating graphene (G) and titania (Ti0.91O2) multilayered nanosheets are fabricated using layer-by-layer electrostatic deposition followed by UV irradiation. Successful assemblies of graphene oxide (GO) and titania nanosheets in sequence with polyethylenimine as a linker is confirmed by UV,vis absorption and X-ray diffraction. Photocatalytic reduction of GO into G can be achieved upon UV irradiation. Ultrafast photocatalytic electron transfer between the titania and graphene is demonstrated using femtosecond transient absorption spectroscopy. Efficient exciton dissociation at the interfaces coupled with cross-surface charge percolation allows efficient photocurrent conversion in the multilayered Ti0.91O2/G films. [source] Electric Field-Directed Convective Assembly of Ellipsoidal Colloidal Particles to Create Optically and Mechanically Anisotropic Thin FilmsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Manish Mittal Abstract A method of simultaneous field- and flow-directed assembly of anisotropic titania (TiO2) nanoparticle films from a colloidal suspension is presented. Titania particles are oriented by an alternating (ac) electric field as they simultaneously advect towards a drying front due to evaporation of the solvent. At high field frequencies (,,>,,25,kHz) and field strengths (E,>,300,V cm,1), the particles orient with their major axis along the field direction. As the front recedes, a uniform film with thicknesses of 1,10,µm is deposited on the substrate. The films exhibit a large birefringence (,n,,,0.15) and high packing fraction (,,=,0.75,±,0.08), due to the orientation of the particles. When the frequency is lowered, the particle orientation undergoes a parallel,random,perpendicular transition with respect to the field direction. The orientation dependence on field frequency and strength is explained by the polarizability of ellipsoidal particles using an interfacial polarization model. Particle orientation in the films also leads to anisotropic mechanical properties, which are manifested in their cracking patterns. In all, it is demonstrated that the field-directed assembly of anisotropic particles provides a powerful means for tailoring nanoparticle film properties in situ during the deposition process. [source] Nanocarving of Titania as a Diffusion-Driven Morphological Instability,ADVANCED FUNCTIONAL MATERIALS, Issue 3 2008Doh-Kwon Lee Abstract Under strongly reducing conditions at high temperatures titania develops a specific surface morphology, comprising a regular array of fibers with a diameter in the sub-micrometer range. By a chemical diffusion experiment in a defined oxygen potential gradient it is shown that this surface structuring is caused by a diffusion-driven morphological instability of an advancing reaction front (surface). The kinetics of the process is analyzed in terms of linear transport equations. The conditions for the occurrence of the surface instability are discussed and the required materials properties are analyzed. The observed surface structuring is not restricted to titania, rather it has to occur in all nonstoichiometric compounds with predominant cation mobility. [source] Inorganic Macroporous Films from Preformed Nanoparticles and Membrane Templates: Synthesis and Investigation of Photocatalytic and Photoelectrochemical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2003D.G. Shchukin Abstract Colloidal dispersions of titania, zirconia, tin oxide, indium oxide, and ceria have been successfully used to impregnate membrane templates and form the respective metal oxide (MO) porous films. The use of alumina and iron oxide sols in the same procedure, however, resulted in compact structures. By mixing different nanoparticle solutions before impregnation, final inorganic films containing two metal oxides, of variable metal oxide ratios, were obtained. The porous inorganic materials were analyzed in terms of surface area, pore size, film thickness, and crystallinity. The mechanism of nanoparticle infiltration and particle adsorption to the template walls is proposed based on the stability of the inorganic film and a study of the influence of either the sol concentration or washing times on the amount of inorganic substance incorporated in the hybrid material. The photocatalytic decomposition of an organic pollutant, 2-chlorophenol, was demonstrated for the porous titania material along with the structures containing mixtures of titania with zirconia, indium oxide, and tin oxide. A ratio of 9:1 TiO2/MO gave the highest photocatalytic activity, which was higher than the activity of Degussa P25 for the TiO2/In2O3 and TiO2/SnO2 systems under the same conditions. The titania films have also been attached to substrates,glass or indium tin oxide (ITO) surfaces,and the photoelectrochemical properties of the porous film attained. A comparison with a spin-coated titania film (prepared from the same colloidal dispersion) showed that the structured porous inorganic film has two times the photoelectrochemical efficiency as the spin-coated film. [source] Infiltrating Semiconducting Polymers into Self-Assembled Mesoporous Titania Films for Photovoltaic Applications,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2003K.M. Coakley Abstract Interpenetrating networks of organic and inorganic semiconductors are attractive for photovoltaic cells because electron transfer between the two semiconductors splits excitons. In this paper we show that films of titania with a uniform distribution of pore sizes can be made using a block copolymer as a structure-directing agent, and that 33,% of the total volume of the film can be filled with a semiconducting polymer. [source] Stabilizers of Particle Size and Morphology: a Road Towards High-Rate Performance Insertion MaterialsADVANCED MATERIALS, Issue 25-26 2009Janez Jamnik It is demonstrated that using a very small amount of ceramic surface stabilizers (not forming coatings) can prevent particle growth and completely preserve their morphology during heating. For the example of titania, a supreme lithium insertion-rate performance is exhibited by such stabilized samples. [source] Photocatalytic Carbon-Nanotube,TiO2 CompositesADVANCED MATERIALS, Issue 21 2009Karran Woan Abstract The literature and advances in photocatalysis based on the combination of titania (TiO2) and carbon nanotubes is presented. The semiconductor basis for photocatalysis is introduced for anatase and rutile. Furthermore, the proposed mechanisms of catalytic enhancement resulting from the pairing of the titania semiconductor with either metallic, semiconducting, or defect-rich carbon nanotubes (CNT) is discussed. Differences are apparent for the mixtures and chemically bonded CNT,TiO2 composites. The article then highlights the recent advances in the synthesis techniques for these composites and their photocatalytic reactions with organic, inorganic, and biological agents. Finally, various applications and challenges for these composite materials are reported. [source] Design of Experiments (DOE) for the Optimization of Titania,hydroxyapatite Functionally Graded CoatingsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2009Valeria Cannillo Titania,hydroxyapatite functionally graded coatings were deposited on titanium alloy substrates by plasma spraying. Because it was necessary to spray together the titania and the hydroxyapatite powders to obtain the graded system, the first target of the present study was to optimize the process parameters in order to obtain a high-quality coating. A 23 Design of Experiments was applied to define the optimal values of plasma torch power, hydrogen flux, and spraying distance. This defined set of parameters (38 kW, 5 SLPM, and 90 mm, respectively) was used to spray the most promising graded coating, which was characterized and postheat treated. [source] Particle size distributions from small-angle scattering using global scattering functionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2004G. Beaucage Control and quantification of particle size distribution is of importance in the application of nanoscale particles. For this reason, polydispersity in particle size has been the focus of many simulations of particle growth, especially for nanoparticles synthesized from aerosols such as fumed silica, titania and alumina. Single-source aerosols typically result in close to a log-normal distribution in size and micrograph evidence generally supports close to spherical particles, making such particles ideal candidates for considerations of polydispersity. Small-angle X-ray scattering (SAXS) is often used to measure particle size in terms of the radius of gyration, Rg, using Guinier's law, as well as particle surface area, S/V, from the Porod constant B and the scattering invariant Q. In this paper, the unified function is used to obtain these parameters and various moments of the particle size distribution are calculated. The particle size obtained from BET analysis of gas adsorption data directly agrees with the moment calculated from S/V. Scattering results are also compared with TEM particle-counting results. The potential of scattering to distinguish between polydisperse single particles and polydisperse particles in aggregates is presented. A generalized index of polydispersity for symmetric particles, PDI = BRg4/(1.62G), where G is the Guinier prefactor, is introduced and compared with other approaches to describe particle size distributions in SAXS, specifically the maximum-entropy method. [source] The effect of water on particle size, porosity and the rate of drug release from implanted titania reservoirsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010Tessy Lopez Abstract The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders. Sol,gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats. The kinetics of the drug release depend on: (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates. The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir. The titanium n -butoxide/water ratio was systematically varied during the sol,gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements. The particle agglomerate size and porosity were found to depend on the amount of water used in the sol,gel reaction. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] Oxidative degradation of 4-nitrophenol in UV-illuminated titania suspensionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Jimmy Lea Abstract An internally-irradiated annular photoreactor has been used to investigate the oxidative degradation of aqueous 4-nitrophenol with titania as the photocatalyst. Reaction runs were performed over a 3-h period and in practically all cases, complete degradation was possible within about 2,h. The kinetics was determined as a function of nitrophenol concentration, oxygen partial pressure, catalyst loading, pH, temperature and light intensity. The reaction was characterised by a relatively low activation energy of 7.83,kJ,mol,1 although transport intrusions were negligible. Rate decreased almost exponentially with pH while a quadratic (maximum) behaviour with respect to both oxygen pressure and nitrophenol concentration is symptomatic of self-inhibition possibly due to the formation of intermediates which competitively adsorb on similar sites to the reactants. Increased catalyst dosage also improved the reaction rate although the possible effects of light scattering and solution opacity caused a drop at loadings higher than about 1.20,g,dm,3. Rate, however, has a linear dependency on light intensity, suggesting that hole,electron recombination processes were negligible at the conditions investigated. © 2001 Society of Chemical Industry [source] Short chain branching profiles in polyethylene from the Phillips Cr/silica catalystJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Paul J. DesLauriers Abstract SEC and on-line Fourier transform infrared spectroscopy analysis have been combined to study branching profiles from the Phillips Cr/silica catalyst. For the first time, catalyst and reactor variables have been shown to affect the overall level and distribution of branches in polyethylene copolymers. Branching profiles from various chromium catalysts have been shown to vary from highly concentrated in the low MW end, to uniformly distributed over all of the MW range. Activation temperature and the presence of titania were highly influential. These observations, which have been used to gain insight into the chemistry of Cr/silica, explain much of the catalyst behavior that has for decades been used to optimize polymer properties. Trends in ESCR, impact resistance, and other physical characteristics, which were long attributed to changes in MW distribution, can now be seen to also be due in large part to changes in the branching profile. This knowledge should be of value in designing future resins. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3135,3149, 2007 [source] Sol,gel microextraction phases for sample preconcentration in chromatographic analysisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 19 2010Scott S. Segro Abstract Sol,gel technology provides a simple and reliable method for solid-phase microextraction (SPME) fiber preparation through in situ creation of surface-bonded organic,inorganic hybrid coatings characterized by enhanced thermal stability and solvent-resistance properties that are important for the coupling of SPME with GC and HPLC, respectively. The sol,gel coating technology has led to the development of an extensive array of sol,gel sorbent coatings for SPME. In this article, sol,gel microextraction coatings are reviewed, with particular attention on their synthesis, characterization, and applications in conjunction with GC and HPLC analyses. In addition, the development of sol,gel-coated stir bars, their inherent advantages, and applications are discussed. Next, the development and applications of sol,gel capillary microextraction (CME) in hyphenation with GC and HPLC is extensively reviewed. The newly emerging germania- and titania-based sol,gel microextraction phases look promising, especially in terms of pH and hot solvent stability. Finally, sol,gel monolithic beds for CME are reviewed. Such monolithic beds are in a position to greatly improve the extracting capabilities and enhanced sensitivity in CME. [source] Preparing titania aerogel monolithic chromatography columns using supercritical carbon dioxideJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2010Ruohong Sui Abstract The search for a method to fabricate monolithic inorganic columns has attracted significant recent attention due to their unique ability in separation applications of various biomolecules. Silica and polymer based monolithic columns have been prepared, but titania and other metal oxide monoliths have been elusive, primarily due to their fragility. This article describes a new approach for preparing nanostructured titania based columns, which offer better performance over conventional particle packed columns for separating a wide variety of biomolecules including phosphopeptides. TiO2 monolithic aerogels were synthesized in separation columns using in situ sol-gel reactions in supercritical carbon dioxide (scCO2) followed by calcination, and compared to those prepared in heptanes. The characterization results show that scCO2 is a better solvent for the sol-gel reactions, providing lower shrinkage with the anatase TiO2 monolith composed of nanofibers with very high surface areas. The monolithic columns show the ability to isolate phosphopeptides with little flow resistance compared to conventional titania particle based microcolumns. [source] Versatile Crack-Free Ceramic Micropatterns Made by a Modified Molding TechniqueJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Marzellus Grosse Holthaus Crack-free ceramic micropatterns made of oxidic ceramic powders, e.g. alumina, titania, zirconia, and nonoxidic calciumphosphate ceramic powders were fabricated by a novel, simple, and low-cost modified micromolding (m-,M) technique via polydimethylsiloxane stamps. By means of this m-,M technique it is possible to fabricate monolithic ceramic bodies with a micropatterned surface with very high accuracy on surface detail. Our produced micropatterns can feature various geometries, e.g. cylinders, holes, channels, and struts with diameters ranging from 8 to 140 ,m in diameter or widths and from 8 to 30 ,m in depth or height. The oxidic and nonoxidic ceramic micropatterns could be removed from the molds and dried without any cracks. Even after sintering, these micropatterned samples showed no cracks or fissures. The reported technique has a very high potential for fully automatized up-scale fabrication of micropatterned ceramic surfaces. [source] Electrodeposition of Titania Thin Films on Metallic Surface for High- k Dielectric ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Biplab K. Roy Current microelectronics devices based on flexible as well as rigid substrates demand high dielectric constant (k) films to be grown on conductive substrate from a low-cost, low-temperature deposition technique. In this study, we produced high- k titania (TiO2) films through an affordable electrodeposition protocol from the electrochemical bath maintained at about 0°C. The deposition occurs through a rapid hydrolysis mechanism of titanium containing ions in the precursor solution aided by electrochemically generated hydroxyl ions formed near the cathode surface (copper (Cu) substrate). Upon attaining a sufficient supersaturation level, such hydrolyzed species precipitate to form a titania thin film on the cathode surface. While depositing from a highly acidic precursor solution, Cu substrate was protected by a cathodic potential (,3 to ,5 V against the counter electrode). The resultant titania films show nanoparticulate structures evolved from nucleation and growth events of the in situ precipitated particles. Much higher deposition rate (about 1 ,m/min) was observed compared with that of typical chemical bath deposition. The resultant films with a thickness of 1500 nm grown on Cu exhibit very high dielectric properties (e.g., k,30, capacitance density >110 nF/in.2 at 100 kHz) and moderate breakdown voltage (VB) (,17.5 V). These properties indicate the potential of electrodeposited titania films to be used as a small-area thin-film capacitor for miniaturized electronic devices. [source] Sonochemical Synthesis of Networked Silica Shell with Reduced Microporosity on Titania Nanocores for Photocatalytic Activity ReductionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Ahmed Mohamed El-Toni Silica shells with a high density of networks and reduced microporosity has been formed on titania nanocores via a sonochemical approach in the absence of ammonia as a hydrolyzing catalyst. The TiO2 -silica core-shell nanoparticles were characterized by transmission electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy (FTIR), and microporosity measurements. The photocatalytic activity of coated titania was also reported. FTIR measurements showed that the silica shell was formed with a high density of networks through the formation of asymmetric Si,O,Si vibration and asymmetric Si,O,Si stretching vibration bonds. Moreover, the thickness and microporosity of the silica shell could be altered by controlling the sonochemical power and time parameters. [source] | |||||||||||||||||||||||||||||||