Changes in Optical Parameters of SiO2:TiO2 Films Obtained by Sol-Gel Method Observed as a Result of Thermal Treatment

The research focused on materials having potential applications in technology of planar evanescent wave sensors. Four samples of binary SiO2:TiO2 thin films having different titania content were manufactured through the sol-gel method and dip-coating technique on polished silicon substrates. The samples were subjected to repeated heating/cooling protocols. Simultaneously, their optical parameters were monitored by spectroscopic ellipsometry as they evolved under varying temperature. Subsequent analysis confirmed linear dependence of refractive index on titania content, at least in vis-NIR wavelengths, as well as a low value of the thermal expansion coefficient. It was shown that the thickness of SiO2:TiO2 films decreased as a result of annealing processes, which may be a consequence of reduced porosity.

Heterostructural transformation of mesoporous silica–titania hybrids

Mesoporous silica (SBA-15 with the BJH pore size of 8 nm) containing anatase nanoparticles in the pore with two different titania contents (28 and 65 mass%), which were prepared by the infiltration of the amorphous precursor derived from tetraisopropyl orthotitanate into the pore, were heat treated in air to investigate the structural changes (both mesostructure of the SBA-15 and the phase and size of the anatase in the pore). The mesostructure of the mesoporous silica and the particle size of anatase unchanged by the heat treatment up to 800 °C. The heat treatment at the temperature higher than 1000 °C resulted in the collapse of the mesostructure and the growth of anatase nanoparticles as well as the transformation to rutile, while the transformation of anatase to rutile was suppressed especially for the sample with the lower titania content (28 mass%). The resulting mesoporous silica-anatase hybrids exhibited higher benzene adsorption capacity (adsorption from water) over those heated at lower temperature, probably due to the dehydroxylation of the silanol group on the pore surface. The photocatalytic decomposition of benzene in water by the present hybrid heated at 1100 °C was efficient as that by P25, a benchmark photocatalyst.

New insight into the role of crosslinkers and composition on selectivity and kinetics of antimony uptake by chitosan-titania composite beads

Role of composition and the nature of crosslinking on the properties of titania-chitosan beads have been investigated in detail. The investigations were done in order to explore the feasibility of design and synthesis of titania-chitosan beads with bespoke functionality based on the intended application. This would greatly enhance the potential for the industrial application of these biopolymer based beads. Beads of varying compositions (of titania and chitosan) were prepared and crosslinked using epichlorohydrin or glutaraldehyde. The physical characteristics and antimony binding properties of the resultant crosslinked titania-chitosan beads were investigated in detail. Influence of chitosan amount on swelling was seen to be more predominant in the glutaraldehyde crosslinked beads (TA-Cts-Glu). TA-Cts-Glu beads showed more swelling and better antimony (Sb(III) and Sb(V)) uptake as compared to the epichlorohydrin crosslinked beads (TA-CTS-Epi). While TA-Cts-Glu beads showed faster uptake kinetics compared to the TA-CTS-Epi beads, the latter showed selectivity towards Sb(III) against transition metal cations. Further, the beads exhibited differential uptake of Sb(V) and Sb(III). TA-Cts-Glu beads prepared with equal amounts of titania and chitosan showed the maximum Sb(V) uptake while the TA-Cts-Epi beads with higher chitosan to titania ratio showed the least. Sb(V) binding was enhanced by the crosslinked chitosan, while the Sb(III) uptake was aided predominantly by the titania content in the beads.

Titanium-Modified MIL-101(Cr) Derived Titanium-Chromium-Oxide as Highly Efficient Oxidative Desulfurization Catalyst

A titanium-chromium-oxide catalyst was prepared by a facile calcination of titanium-modified MIL-101(Cr). The resulting material, possessing a surface area of 60 m2 g−1 and a titania content of 50.0 wt%, can be directly used as the catalyst for oxidative desulfurization (ODS) reaction of dibenzothiophene (DBT). This novel ODS catalyst can remove 900 ppm sulfur-containing compounds in a reaction time of 30 min at 60 °C. The experimental results showed that the specific activity increased with the titanium content. The specific activity of the catalyst with 50%Ti reached 129 μmol/m2, which was much higher than that of reported Ti-based catalysts.

Vapour-phase conversion of methyl lactate into lactide over TiO2/SiO2 catalyst at the lowered pressure

Now polylactide (PLA) widely use as biodestructive packing material. Usually monomeric lactide produce from lactic acid. Also, methyl (ethyl) lactate could be used for lactide obtaining via its vapour-phase condensation on TiO2/SiO2 catalyst at 2600C in N2 carrier-gas flow. However, at that it is necessary to heat carrier-gas to the reaction temperature. In this communication the results on methyl lactate vapour condensation into lactide with the lowered pressure of 100-150 mbar, without carrier-gas, are presented. Supported TiO2/SiO2 catalyst with 5 wt.% titania content has been prepared by impregnation of silica with Ti(OC4H9)4. After calcination at 5000C prepared catalyst has amorphous mesoporous structure with 335 m2/g surface area and 0.83 сm3/g pore volume. The catalytic experiments were performed in such way. Liquid methyl lactate was dosed into the evaporator (2500C) and further in the flowing reactor (2600C) under pressure of 100 mbar that produced by vacuum pump. Load on a catalyst was varied from 25 to 55 mmol ML/(gcath). Cooled product was analyzed on Agilent 7820A chromatograph and NMR Bruker Avance-400 spectrometer. It was shown that TiO2/SiO2 catalyst provide 74% selectivity towards lactide at 50-53% methyl lactate conversion with lactide productivity of 7.8 mmol L/(gcath) at 2600C/100 mbar. The catalyst stable work is more 80 h. Main impurities are methyl lactoillactate, 1-methoxyethanol and 1,1-dimethoxyethane.

Influence of the Titania Content on the Microstructure and Properties of Plasma Sprayed Alumina-Titania Coatings

The composite alumina-titania coatings have been widely used in industry fields to protect metallic components from wear, corrosion and thereby prolonging their service time. This paper presents an analysis of the microstructure and mechanical properties of Al2O3-TiO2 composite coatings, plasma sprayed on steel substrates from feedstocks containing various concentrations of the TiO2 powder. The coatings revealed lamellar microstructure, formed by the rapid solidification of molten droplets of the powder on previously deposited splats. The main phase identified in the coatings was γ-Al2O3 phase, the others were TiO2 and α-Al2O3, as well as amorphous phase. The results indicated significant improvement of hardness, Young’s modulus and fracture resistance of coatings with an increase in TiO2 from 3 wt. % to 13 wt. %. The friction coefficient was found to be the same for both coatings.