XPS and XAES study of titania-silica mixed oxide system

Stakheev, A. Yu.; Shpiro, E. S.; Apijok, J.

doi:10.1021/j100123a034

Cited by 201 publications

(126 citation statements)

References 1 publication

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“…21 In the solid phase, no thermodynamically favorable mixed oxide phase of SiO 2 and TiO 2 exists. 36 Phase segregation as predicted by the phase diagram was also observed by Ehrman et al 21 in flamemade silica/titania particles with 20-90 wt% TiO 2 and by Stakheev et al 33 in wet-made silica/titania particles with 10-85 wt% TiO 2 . Schultz et al 37 experimentally observed, however, the solubility of titania in silica glasses containing up to 12 wt% TiO 2 .…”

Section: B Particle Sampling and Analysissupporting

confidence: 62%

Flame-coating of titania particles with silica

Teleki¹,

Pratsinis²,

Wegner³

et al. 2005

J. Mater. Res.

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Silica/titania composite particles were prepared by co-oxidation of titanium-tetra-isopropoxide and hexamethyldisiloxane in a co-flow diffusion flame reactor. The influence of precursor composition on product powder characteristics was studied by x-ray diffraction, nitrogen adsorption, electron microscopy, elemental mapping, and energy-dispersive x-ray analysis. The flame temperature was measured by Fourier transform infrared spectroscopy. The evolution of composite particle morphology from ramified agglomerates to spot-or fully coated particles was investigated by thermophoretic sampling and transmission/scanning electron microscopy. At 40-60 wt% TiO 2 , particles with segregated regions of silica and titania were formed, while at 80 wt% TiO 2 rough silica coatings were obtained. Rapid flame-quenching with a critical flow nozzle at 5 cm above the burner nearly halved the product particle size, changed its crystallinity from pure anatase to mostly rutile and resulted in smooth silica coatings on particles containing 80 wt% TiO 2 .

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Section: B Particle Sampling and Analysissupporting

confidence: 62%

Flame-coating of titania particles with silica

Teleki¹,

Pratsinis²,

Wegner³

et al. 2005

J. Mater. Res.

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“…The two interfaces exhibit clear differences: in the first one (interface A), the decrease of both signals connected to the presence of Ti atoms and to the existence of Ti-O octahedral environments are well correlated within one probe step. In the second one (interface B), the decrease of the weight of the Ti-O antibonding orbital is faster than the decrease of the number of Ti atoms, suggesting therefore the existence of some mixed Ti02-Si02 solid solution with Si-O-Ti bonds [12] in a zone of about 5 nm width. A final criterion is the visibility of the crystal-field splitting on both Ti L lines and 0 K prepeak, which is representative of the quality of the local crystal symmetry.…”

Section: Expérimental Resultsmentioning

confidence: 98%

Spatially Resolved EELS Fine Structures at a SiO₂/TiO₂ Interface

Brun

Colliex

Rivory

et al. 1996

Microsc. Microanal. Microstruct.

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Abstract. 2014 SiO2/TiO2 multilayers stacks used in optical coatings have been studied by Electron Energy Loss Spectroscopy (EELS). The line-spectrum mode has been used: the incident electron probe of the STEM is scanned under digital control on the specimen surface in the direction perpendicular to the layers, while the whole spectrum is acquired. The selected energy range contains Ti L23 and O K edges, in order to study the evolution of the fine structures visible on these edges. Every experimental spectrum is then fitted with a linear combination of the two reference spectra (TiO2 and SiO2) extracted from the same sequence. It is possible to identify in the neighbourhood of the interface some EELS fine structures which cannot be fitted to a combination of reference spectra, but are representative of hybrid environments, such as Si-O-Ti in the present study. A quantitative analysis of the changes in different fine structures on the titanium and oxygen edges enables to clearly discriminate different levels of interdiffusion at the boundary.

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“…According to the literature data [76][77][78][79][80][81] species is between 456.2 and 457.4 eV. The X-ray absorption spectra are shown in Fig.…”

Section: In Situ Nap Xps Xanes and Tpr Studymentioning

confidence: 90%

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

121

150

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address: vvk@catalysis.ru (V.V. Kaichev). A B S T R A C TThe methanol oxidation over highly dispersed vanadium oxide supported on TiO 2 (anatase) has been investigated by in situ Fourier transform infrared spectroscopy (FTIR), near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), X-ray absorption near edge structure (XANES), and temperature-programmed reaction spectroscopy. The data were complimented with kinetics measurements in a flow reactor. It was found that at low temperatures dimethoxymethane competes with methyl formate, whereas the production of formaldehyde is greatly inhibited. FTIR shows the presence of non-dissociatively adsorbed molecules of methanol, as well as adsorbed methoxy, dioximethylene, and formate species under reaction conditions. According to the NAP XPS and XANES data, the reaction involves the reversible reduction of V 5+ cations, pointing that the vanadia lattice oxygen participates in the methanol oxidation through the classical Mars-van Krevelen mechanism. The detailed mechanism of the methanol oxidation on vanadia catalysts is discussed.

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XPS and XAES study of titania-silica mixed oxide system

Cited by 201 publications

References 1 publication

Flame-coating of titania particles with silica

Flame-coating of titania particles with silica

Spatially Resolved EELS Fine Structures at a SiO₂/TiO₂ Interface

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

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XPS and XAES study of titania-silica mixed oxide system

Cited by 201 publications

References 1 publication

Flame-coating of titania particles with silica

Flame-coating of titania particles with silica

Spatially Resolved EELS Fine Structures at a SiO2/TiO2 Interface

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

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Spatially Resolved EELS Fine Structures at a SiO₂/TiO₂ Interface