Control of the polymerization process of multicomponent (Si, Ti, Zr) sols using chelating agents

Méndez-Vivar, J.; Mendoza-Serna, R.; Valdez-Castro, L.

doi:10.1016/s0022-3093(01)00644-5

Cited by 40 publications

(16 citation statements)

References 22 publications

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“…Those were also observed between 2400 and 3800 cm -1 , in samples roasted below 600 °C (Nagarajan and Rajendran, 2009;Ryskin, 1974). The absorption band at 1080 cm -1 observed in all samples is attributed to Si-O bonds in SiO 4 tetrahedral groups (Farmer, 1974;Vicente-Rodriguez et al, 1996;Méndez-Vivar et al, 2001;Ratnasamy et al, 2004). Above 700 °C a weak shoulder is observed at 1130 cm -1 which can be attributed to Ti-O bonds in TiO 4 as well as to O -O stretching in metal oxide -metal oxide end configuration in solid solutions (Ratnasamy et al, 2004).…”

Section: Alkali Decomposition Reactionmentioning

confidence: 91%

Titania recovery from low-grade titanoferrous minerals

2011

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In this study a novel process for extraction of titanium valuables from its minerals is presented. The process entails roasting of titanium ore with alkaline metal salt, hydrolysing fused cake and dissolution in acid. Optimum conditions were found to be 1 hr fusion at 850 °C, using 2:1 mole ratio, NaOH:FeTiO 4 , irrespective of the particle size interval used in this work. It was found that under these conditions » 80% of titanium was recovered. Na 0.75 Fe 0.75 Ti 0.25 O 2 , NaFeTiO 4 and Na 2 Fe 2 Ti 3 O 10 were the dominant phases at this temperature. The presence of these phases is viewed as beneficial to the economics of the process, it consumes less NaOH. Fusions conducted at 550 °C or below produced chiefly binary phases, Na 2 TiO 3 and NaFeO 4 , reducing process economy. Optimum leaching conditions were S/L= 0.26, leaching at 75 ºC, for 15 min. 85% of NaOH were recovered, under these conditions. Leaching obeys shrinking core mechanism model. IntroductionTitania (TiO 2 ) is a white pigment used in paints, paper, plastics, cosmetics and coatings. Its wide application is due to its higher opacity and covering power. There are two commercial methods of TiO 2 production, the chloride and the sulphate process. In the chloride process titanium mineral is converted into TiCl 4 which is subsequently oxidized at high temperatures.In the sulphate process the ore is converted into sulphate solution and then thermally hydrolysed to hydrous titanium. The later is calcined to produce the pigment (Braun et al, 1992;Nielsen and Chang, 1996;Xue et al, 2009).According to Pong et al (1995) a commercially viable process has to be environmentally benign, to generate a minimum waste, be able to use all grades of ores and be economically favourable. The above processes are, either environmentally unfriendly, costly, generate high levels of waste or recycle, are unable to process low grade ores, as well as, ores such as anatase, sphene, and perovskite (Bulatovic, 1999;Cole, 2001;Nielsen and Chang, 1996;Van Dyk et al, 2004;Yuan et al, 2005).Generally low grade titanoferrous ores are submitted to slagging process. The slagging process however faces uncertain future due to its higher energy consumption and green house gases emission. Additionally slagging is unable to treat radioactive ores, since the radionuclides remain in the solid solution during slagging process. With increasingly restringent environmental policies on radionuclides content, further treatment has to be conducted to reduce it. This will result in additional production costs (Nielsen and Chang, 1996; Habashi, 1997;Doan, 2003; Jha et al, 2005;Lahiri et al, 2006;Lahiri and Jha, 2007

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Section: Alkali Decomposition Reactionmentioning

confidence: 91%

Titania recovery from low-grade titanoferrous minerals

2011

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“…The presence of this hydrocarbon unit reveals a certain degree of planarization of the coating macromolecular chains. Water molecules show an intense characteristic absorption band between 3400 and 3600 cm -1 assigned to O-H stretching in H-bonded water [35]. No significant peaks were observed between 3400 and 3600 cm -1 in these coatings.…”

Section: Atr-ftir Analysismentioning

confidence: 87%

“…It is probably due to formation of the chelate complex between Zr and acetic acid. A weak absorption peak at around 2928 cm -1 is related to CH 2 group incorporated into the silica group [35]. The presence of this hydrocarbon unit reveals a certain degree of planarization of the coating macromolecular chains.…”

Section: Atr-ftir Analysismentioning

confidence: 98%

Preparation and evaluation of corrosion behavior of GPTMS–TEOS hybrid coatings containing Zr and Ce on aluminum alloy 6061-T6

Bahrami

Borhani

Bakhshi

et al. 2015

J Sol-Gel Sci Technol

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Environmentally friendly organic-inorganic hybrid coatings with different amount of Ce and Zr content were prepared by a sol-gel method and deposited on aluminum alloy 6061-T6. Attenuated total reflectance-Fourier transform infrared spectroscopy and scanning electron microscopy were used to structural study of the hybrid coatings. Adhesion strength of sol-gel coatings to the substrate was also evaluated using pull-off test. Corrosion behavior of the samples was evaluated by cyclic potentiodynamic and linear polarization tests. The obtained results display that adhesion strength of the coatings was enhanced with an increase in zirconium and cerium content. Corrosion analysis showed a decrease in corrosion current density of coated samples two to four orders of magnitude compared to the bare alloy 6061. Decreasing in corrosion current density and increasing in polarization resistance were observed by an increase in Zr and cerium content. The sol-gel-coated layer doped with 20 g/l cerium nitrate offered excellent protection against corrosion. Unlike the bare alloy 6061, the crack-free samples showed no sensitivity to pitting corrosion. Graphical Abstract The present investigation has been based on preparation of hybrid sol-gel coatings with different amount of zirconium and cerium content using dip coating method. Effect of cerium and zirconium content on thickness, adhesion strength and pitting corrosion behavior of the coatings were investigated. Significant decrease in corrosion current density was observed compared to uncoated substrate. Increase in polarization resistance was observed by an increase in zirconium and cerium content.

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“…The Si sol precursor was a so-called A2 sol. The detailed procedure for the preparation of the A2 sol can be seen elsewhere [15][16][17]. The Ti precursor was chelated with acacH and isoH separately with the molar ratio of chelating agent/Ti = 2.0.…”

Section: Methodsmentioning

confidence: 99%

SiO2-TiO2 membranes by the sol-gel process

Méndez-Vivar

Mendoza-Serna

2006

Silicon Chem

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The use of membranes for gas separation represents an important alternative from the viewpoint of energy conservation in industrial separation processes. Polymeric Si-Ti sols prepared from titanium isopropoxide (Ti(OPr i ) 4 ) and tetraethoxysilane (TEOS) were used to deposit membranes on α-Al 2 O 3 supports. Acetylacetone (2,4 pentanedione, acacH) and isoeugenol (2-methoxy-4-propenylphenol, isoH) were employed separately to chelate the Ti precursor in order to slow down the chemical reactivity, avoiding precipitation. The radial distribution functions (RDF) of the gels aging at room temperature were obtained. The xerogels were studied by Thermal Gravimetric (TGA) and Differential Thermal (DTA) Analysis in air. The Microporosity of the solids calcined at 773 K was determined by N 2 -adsorption at 77 K. The membrane thickness was determined from SEM photographs. Preliminary permeance results of the supported membranes on commercial alumina support were obtained for He, N 2 and CO 2 in a single gas equipment. At 773 K the separation factors α(He/CO 2 ) and α(N 2 /CO 2 ) for both membranes exceeds the theoretical Knudsen limit.

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Control of the polymerization process of multicomponent (Si, Ti, Zr) sols using chelating agents

Cited by 40 publications

References 22 publications

Titania recovery from low-grade titanoferrous minerals

Titania recovery from low-grade titanoferrous minerals

Preparation and evaluation of corrosion behavior of GPTMS–TEOS hybrid coatings containing Zr and Ce on aluminum alloy 6061-T6

SiO2-TiO2 membranes by the sol-gel process

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