Morphology and photoluminescence study of titania nanoparticles

Titania nanoparticles are prepared by sol–gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)-block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol–gel components—hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer—are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol–gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13–20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies

Glass-ceramics and composites containing aluminum borate whiskers

Glass\u2013ceramics and composites containing aluminum borate whisker crystals were developed using two different approaches: crystallization of an aluminum borosilicate glass or addition of an aluminum borate precursor powder to a glass frit. Two different glass frits were used, a commercially available borosilicate glass or the same aluminum borosilicate glass used in the crystallization experiments. X-ray diffraction analysis showed that Al4B2O9 or Al18B4O33 whiskers formed in all samples, indicating that the glass crystallized significantly with increasing heating temperature, and that the precursor can be effectively be used to generate in situ aluminum borate crystals within glass matrices. However, the samples produced by mixing the aluminum precursor with glass frits contained porosity after processing, indicating that pressureless viscous sintering was not efficient. The hardness of the glass\u2013ceramic did not vary significantly with processing temperature, but the (indentation) fracture toughness measured showed a >100% increase (after heating at 1200 8C), demonstrating that whisker-shaped crystals are effective in increasing the mechanical toughness of the glass matrix. The hardness of the composites showed a dependence on the amount of aluminum borate crystals present

Effect of tin-oxide on the physical properties of soda-lime-silica glass

The effect of tin-oxide on the physical properties of soda-lime-silica glasses was investigated. Glasses containing tin-oxide concentrations ranging from 0 to 3 mol% were synthesized in the laboratory. In some of the glasses, an attempt was made to control the ratio of Sn2+ to Sn4+ present in the glass. Dilatometry, beam-bending viscosity, and sonic resonance experiments were performed on the glasses to determine the role of tin on the thermal expansion, glass transition temperature, ditatometric softening temperature, annealing temperature, strain temperature, and elastic modulus of the glass. Mossbauer spectroscopy was used to determine the presence and relative amount of Sn2+ and Sn4+ in the glasses. The data suggest that the substitution of relatively small amounts of tin for a modifier species in the glass composition results in an increase in the network connectivity. In addition, the results suggest that this increase in network connectivity is more apparent in glasses containing higher relative amounts of Sn4+ Compared to Sn2+. (c) 2005 Published by Elsevier B.V

Tribology-Structure Relationships in Silicon Oxycarbide Thin Films

Silicon oxycarbide is a versatile material system that is attractive for many applications because of its ability to tune properties such as chemical compatibility, refractive index, electrical conductivity, and optical band gap through changes in composition. One particularly intriguing application lies in the production of biocompatible coatings with good mechanical properties. In this paper, we report on the wide range of mechanical and tribological property values exhibited by silicon oxycarbide thin films deposited by reactive radio frequency magnetron sputtering. Through a change in oxygen partial pressure in the sputtering plasma, the composition of the films was controlled to produce relatively pure SiO2, carbon-doped SiC, and compositions between these limits. Hardness values were 8\u201320 GPa over this range and the elastic modulus was measured to be between 60 and 220 GPa. We call attention to the fit of the mechanical data to a simple additive bond-mixture model for property prediction. Tribological parameters were measured using a ball-on-disk apparatus and the samples exhibited the same general trends for friction coefficient and wear rate. One film is shown to produce variable low friction behavior and low wear rate, which suggests a solid-state self-lubrication process because of heterogeneity on the nanometer scale

Commercial and laboratory prepared titanium dioxide thin films for self-cleaning glasses: Photocatalytic performance and chemical durability

A TiO2-based photocatalytic film on glass for self-cleaning purposes was prepared via sol\u2013gel. This film exhibits similar physical and chemical properties, including; (1) surface composition and chemistry, (2) crystal phase and size, (3) UV transmission, and (4) surface roughness/morphology, as commercially available (CVD-based) films. In addition the sol\u2013gel derived, laboratory films deposited on glass exhibits comparable, or in some cases better photocatalytic performance than the commercially available films on glass. Photocatalytic performance of the commercial and laboratory prepared films are determined and are discussed in context of their material properties/ characteristics. Furthermore films are reacted in model solutions (neutral, acidic, and basic) which in turn not only cause changes in the surface composition and roughness of the films, but also cause an increase in the photocatalytic performance