Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

Sinkó, Katalin

doi:10.3390/ma3010704

Cited by 137 publications

(78 citation statements)

References 226 publications

(401 reference statements)

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“…The silicon atoms carry substantially less positive charge; thus, the hydrolysis and condensation reaction of silicon alcoxides occur at much lower rates [8]. This order corresponds to the reactivity sequence of tetravalent alcoxides in hydrolysis reactions: Si(OiPr)4<< Ti(OiPr)4<Zr(OiPr)4 [9]. It is supposed that phase formation is caused by the used molar % alcoxides into primary sol.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Micro- and Mesoporous SiO2 Based Ceramic Materials (Using Sol-gel Technology)

Karpe

Mežinskis

2014

Material Science and Applied Chemistry

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-The aim of research is to develop an area of microand mesoporous ceramic materials of ternary -TiO2-ZrO2-SiO2 system. Ceramic system TiO2-ZrO2-SiO2 has been synthesized via a sol-gel technology by hydrolysis of tetraethylorthosilicate (TEOS) and zirconia propoxide and titanium isporopoxide solutions. The sols have been polymerized at room temperature to obtain gels and dried at 100 °C for 72 hours. Xerogel has been milled for 1 or 6 hours and axially pressed for nanoporous ceramic samples. Powders have been sintered at 800 °C or 1000 °C in air. 1 M hydrochloric acid and distilled water have been used as a catalyst to advance the hydrolysis and condensation reactions. All samples have been characterized by X-ray (XRD) diffraction, particle size distribution, crystallite size distribution, compressive strength. Porosity and specific surface area of nanoporous ceramic samples have been determined by Brunauer, Emmett and Teller (BET) nitrogen adsorption-desorption isotherms.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Micro- and Mesoporous SiO2 Based Ceramic Materials (Using Sol-gel Technology)

Karpe

Mežinskis

2014

Material Science and Applied Chemistry

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“…The bonds of SiO2 can be characterized by about 50 % covalent feature. This order corresponds to the reactivity sequence of tetravalent alcoxides in hydrolysis reactions: Si(OiPr)4<<Ti(OiPr)4<Zr(OiPr)4 [11]. Zirconium titanate is an intermediate compound in the binary system ZrO2-TiO2.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Nanoporous SiO2-TiO2-ZrO2 Ceramics Using Sol-gel Technology

Karpe

Mežinskis

Timma

2014

Material Science and Applied Chemistry

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-The aim of research is to develop an area of nanoporous ceramics of ternary systems. Nanoporous ceramic system SiO2-TiO2-ZrO2 has been synthesized via sol-gel technology by hydrolysis of tetraethylorthosilicate (TEOS), zirconia and titanium alcoxides solutions. The sols have been polymerized at room temperature to obtain gels and dried at 100 o C, then milled for 1 or 6 hours for particle homogenization, pressed into samples, and then sintered at 800 o C or 1000 o C in air. The samples have been characterized by XRD, particle size distribution, crystallite size distribution, compressive strength. Porosity of ceramic samples has been determined by nitrogen adsorption-desorption isotherms.

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“…Because the lowest reaction rate for hydrolysis occurs at pH = 7 [29], a lot of silica networks are still unreacted, so the electrophilic tendency of condensation terminates, and the alcohol condensation mechanism becomes favourable [30,31]. This condition gives rise to more locally branched networks, leading to narrow pore sizes and small pore volumes, thus giving rise to dense network and then low transparency.…”

Section: Discussionmentioning

confidence: 99%

Tuned optical transmittance in single-step-derived silica aerogels through pH-controlled microstructure

et al. 2017

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We have systematically studied the relationship between synthesis pH and morphological and optical properties of silica aerogels. We have determined through SEM and BET that there is a systematic correlation between the pH of the initial silica solution and the surface area, porosity, and pore size of the resulting aerogel. We find that optical transmittance, particularly its wavelength dependence (dispersion), is strongly governed by the microstructure and, therefore, synthesis pH. We have determined that the microstructure of the aerogels fall into three broad categories: monostructural, which is characterized by repeating elongated microstructural features; fractal, which shows a distinctive structure that is emulated on multiple length scales; and isotropic, which is characterized by having no distinct features in its microstructure. Simply by controlling the pH of the synthesis environment, we can tune the optical properties of silica aerogels through pH controlled the microstructural modification. We have found that pH = 1-5 gives high dispersion, pH = 6-7 results in low transmittance and low dispersion, pH = 8 shows the highest transmittance with the lowest dispersion, and pH = 9-10 transitions back to lower transmittance and higher dispersion.

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Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels

Cited by 137 publications

References 226 publications

Synthesis of Micro- and Mesoporous SiO2 Based Ceramic Materials (Using Sol-gel Technology)

Synthesis of Micro- and Mesoporous SiO2 Based Ceramic Materials (Using Sol-gel Technology)

Synthesis of Nanoporous SiO2-TiO2-ZrO2 Ceramics Using Sol-gel Technology

Tuned optical transmittance in single-step-derived silica aerogels through pH-controlled microstructure

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