The composites xTiO 2 -(1-x)SiO 2 (x = 0.1, 0.5, 0.9) were obtained by coprecipitation from solutions of alkoxides: tetraethoxysilane (TEOS) and titanium tetraisopropoxide (TIPT). Intermolecular interaction of the components of the composite is apparent in the IR absorption spectra in the 928-952 cm -1 region, and is connected with bending vibrations of the Si-O-Ti bond.Introduction. Composites based on titanium and silicon dioxides have begun to be used relatively recently as catalysts and photocatalysts for various processes, protective coatings, components of glasses with low linear thermal expansion coefficient, and waveguide materials [1][2][3][4][5][6][7]. The method for obtaining the composite determines the nature and extent of interactions between components. For mechanical mixing of the individual phases, weak van der Waals interaction occurs. Thorough mixing of the components at the molecular level when obtaining the composite by sol-gel or coprecipitation methods leads to a substantial change in the properties of the end product: the appearance of new catalytically active centers, a shift in the onset of crystallization for the titanium-containing component toward higher temperatures, and accordingly an increase in the thermal stability of the structural and adsorption characteristics of the composite [7]. Formation of Si-O-Ti bonds at the TiO 2 -SiO 2 interface leads to an appreciable change in the electronic structure of the titanium atoms in the composite [8,9]. One possible method for estimating the interaction between components is IR spectroscopy. The absorption band observed in the 910-960 cm -1 region is due to characteristic vibrations of the Si-OH and Si-O-Ti bonds. Its position depends on the chemical composition of the sample and the resolution of the instrument [10,11]. We know that for exhaustive dehydration of SiO 2 , the band in the 940-950 cm -1 region, due to bending vibrations of the Si-OH bond, disappears in the absorption spectra. After appropriate heat treatment of the composite, absorption in this region will be due only to bending vibrations of the Si-O-Ti bond and thus it becomes possible to study the nature and extent of intermolecular interaction between titanium and silicon oxides by IR spectroscopy, which was the subject of this work.The Experiment. The composite was obtained by the coprecipitation method. For this purpose, the specified amounts of tetraethoxysilane (TEOS) and titanium tetraisopropoxide (TIPT) were mixed with isopropyl alcohol, then a solution of water (or ammonium hydroxide) in alcohol was added dropwise with vigorous stirring. The suspension was stirred for 1 h, the residue was separated by filtration and washed with water until the organic components were no longer present. The samples were dried at 120 o C for 5 h and calcined at 350 o C and 650 o C for 3 h. The individual titanium and silicon oxides were obtained under similar conditions. Table 1 gives the conditions for obtaining powders of the individual titanium and silicon oxides and the composit...

Corrosion inhibition of aluminum alloy AA6063-T5 by vanadates (NaVO 3 ) in 0.05 M NaCl solution has been investigated by electrochemical and weight loss measurements, and associated with microstructure and Volta potential data. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses confirmed the presence of micrometer-sized Fe-rich Al 4.01 MnSi 0.74 , Al 1.69 Mg 4 Zn 2.31 , and FeAl 3 intermetallic phases (IMPs) and nanometer-sized CuAl 2 , ZnAl 2 , and Mg 2 Si precipitates in the microstructure. Scanning Kelvin probe force microscopy measurements showed Volta potential differences of up to 600 mV between the microstructure constituents indicating a high susceptibility to micro-galvanic corrosion, with interphase boundary regions exhibiting the highest propensity to corrosion. Most IMPs had cathodic character whereas some nanometer-sized Mg-rich particles exhibited anodic nature, with large Volta potential gradients within interphase regions of large cathodic particles. Electrochemical potentiodynamic polarization measurements indicated that the vanadates provided mixed corrosion inhibition effects, mitigating both oxygen reduction, occurring on cathodic IMPs, and anodic metal dissolution reaction, occurring on anodic sites, such as Mg 2 Si and interphase boundary regions. Electrochemical measurements indicated that the sodium metavanadate inhibitor blocks active metal dissolution, giving high inhibition efficiency (>95%) during the initial exposure, whereas long-term weight loss measurements showed that the efficacy decreases after prolonged exposure. Aluminum and its alloys are attractive materials for a range of industrial applications due to cost-efficient recyclability, excellent physical and mechanical properties, such as low density, high thermal conductivity, good weldability, and high strength-to-weight ratio. [1][2][3][4] In particular, the 6xxx-series (Al-Mg-Si) alloys are widely used in aerospace, automotive, marine, and construction industries due to their relatively good corrosion resistance, formability, and low cost as compared to the 2xxx (Al-Cu) and 7xxx (Al-Zn) alloys.5-7 However, these alloys contain multiple alloying elements and their microstructure is very heterogeneous, typically consisting of a large variety of intermetallic phases (IMPs), which makes them highly susceptible to localized corrosion such as pitting or intergranular corrosion. 5,8,9 While nanometer-sized IMPs, dispersed in the Al matrix, are desirable for mechanical strength of Al alloys, micrometer-sized IMPs may induce localized corrosion due to micro-galvanic coupling between the Al matrix and the IMPs, 10-12 which may also affect the anodization process. 13,14 IMPs play an important role in localized corrosion since their type, size, and distribution can affect electrochemical reactions, homogeneous chemical reactions as well as transport phenomena of molecular and ionic species. 8,15,16 Therefore, detailed knowledge about IMPs in the Al alloy is needed when exploring the mechanism ...

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