Synthesis and Transformation of Hollow Rutile Titania Wires by Single Spinneret Electrospinning with Sol-Gel Chemistry

The work described below was carried out to understand how to control the morphology of nanostructured titania calcined from electrospun nanofibers. This is the first report of hollow rutile nanofibers synthesized from electrospun nanofibers with short calcination time. Titanium isopropoxide was incorporated into the nanofibers as the titania precursor. The electrospinning technique was used to fabricate ceramic/polymer hybrid nanofibers. The electrospun nanofibers were then calcined to produce rutile titania nanofibers with different morphologies (hollow or solid nanofibers), which were characterized by SEM and TEM. The initial concentration of ceramic precursor and the calcination time were shown to control the morphology of the nanofiber. The hollow morphology was only obtained with a concentration of the precursor within a certain level and with short calcination times. The heat treatment profile contributed to particle growth. At longer times, the particle growth led to the closure of the hollow core and all the nanofibers resembled strings of solid particles. A formation mechanism for the hollow nanofibers is also proposed.

Carbon-coated Single-phase Ti4O7 Nanoparticles as Electrocatalyst Support

The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applications. This work demonstrates a synthesis of carbon-coated Magnéli phases TiOx (TiOx@C) nanoparticles from 3-aminophenol and rutile titania (TiO2) nanoparticles as a support for platinum (Pt) electrocatalyst. 3-aminophenol was polymerized and carbonized on the surface of TiO2 nanoparticles respectively in a microwave hydrothermal reactor and a tubular furnace. Reduction of the carbon-coated TiO2 (TiO2@C) into TiOx@C was performed in hydrogen atmosphere at 800-1050 °C. The carbon coating effectively prevented TiO2 nanoparticles from sintering, resulted in TiOx@C sizes from 50 to 100 nm. Single-phase Ti4O7 core, which has the highest theoretical electrical conductivity among the Magnéli phases, was obtained from reduction of TiO2@C at 1000 °C. for 10 min C/Ti4O7-supported Pt exhibited an electrochemical surface area of 46 m2 mgPt-1 at 15% Pt loading, slightly higher than that reported for commercial TKK electrocatalyst with 20% Pt loading (44.13 m2 mgPt-1).

Preparation and Characterization of Rutile Titania Nanofluids Stabilized in Different Surfactants Base Fluids

Background: Improvement of conventional heat transfer fluids for achieving higher energy efficiencies in thermal equipment is a key parameter to conserve energy in industries. The heat transfer fluids such as water, oil and ethylene glycol greatly suffer low heat transfer performance in industrial processes. There is a need to develop new types of heat transfer fluids that are more effective in terms of heat transfer performance. Nanofluids enhance thermal conductivity and improve the thermal performance of heat transfer systems. Methods: New titania nanofluid samples consisting of 0.0625 to 1% TiO2 nanoparticles were prepared and characterized. The method of preparation was based on prior precipitation of TiO2 from an ammoniacal solution of pH 9 and calcination at 900°C. Solubilization, homogenization and stabilization of the of the nanoparticles were performed by sonication in the presence of sodium dodecyl sulfate (SDS) anionic surfactant and cetyltrimethylammonium bromide (CTAB) cationic surfactant. Results: This treatment was also utilized to increase the stability and improve the thermal properties of the fluid. Conclusion: Several characterization techniques including measurements of hydrodynamic size distribution, zeta potential, transmission electron microscopy (TEM), viscosity, density, specific heat, thermal conductivity, and sedimentation photo capturing were used to measure and confirm the stability and sedimentation rate of the prepared nanofluids.

Co-Catalytic Action of Faceted Non-Noble Metal Deposits on Titania Photocatalyst for Multielectron Oxygen Reduction

In order to clarify the reason of often reported low photocatalytic activity of rutile titania compared to that of anatase titania and the sluggish kinetics for oxygen reduction of rutile titania, in this study, faceted copper(I) oxide (Cu2O) particles (FCPs), i.e., cube, cuboctahedron and octahedron, were deposited onto rutile particles by an in-situ wet chemical method, and the co-catalytic action of FCPs was studied in the oxidative decomposition of acetic acid. The oxygen reduction reaction kinetics of bare and FCP-loaded titania samples in photodecomposition of organic compounds were investigated by light-intensity dependence measurement. FCPs serve as the specific sites (sink) which accumulate excited electrons to drive multielectron oxygen reduction reactions, as the counter reaction in photodecomposition of organic compounds by positive holes, which significantly improves the photocatalytic activity of rutile titania particles.