Sol–Gel Synthesis of Microporous Amorphous Silica from Purely Inorganic Precursors

Muñoz-Aguado, M.J.; Gregorkiewitz, M.

doi:10.1006/jcis.1996.4564

Cited by 44 publications

(33 citation statements)

References 4 publications

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“…When such mechanisms prevail, then according to Muñoz-Aguado and Gregorkiewitz 40 , a microporous texture is expected for the silica matrix. There have also been reports of the silica particles tending to form a linear chain, with low crosslink density, at low pH values 41 .…”

Section: Figurementioning

confidence: 94%

Production of Porous Silica Microparticles by Membrane Emulsification

et al. 2011

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Section: Figurementioning

confidence: 94%

Production of Porous Silica Microparticles by Membrane Emulsification

et al. 2011

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“…TEOS hydrolysis at high pH has been shown to lead to a high number of undercoordinated Q2 and Q3 sites, resulting in a higher micropore volume. 28 The influence of the precipitating agent on silica thermal stability is poorly understood but TEM images suggest that flocculation with methanol leads to less aggregated SiO 2 /TMO flocs as compared with acetone and isopropanol (results not shown). We find support for this hypothesis from TEM images of SiO 2 /TMO flocs precipitated with less than the recommended amount of methanol in the procedure.…”

Section: Representative Resultsmentioning

confidence: 99%

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

Hunt

Román‐Leshkov

2015

JoVE

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A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 °C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 °C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 °C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder. Video LinkThe video component of this article can be found at

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“…The silica sol-gel transition may occur due to the percolation of nanoparticles (Iler, 1979). Munoz-Aguard and Gregorkiewitz (1997) and Knoblich et al (2001) researched the mechanism of silica sol-gel transition by using 29 Si NMR spectra and small angle X-ray scattering, respectively. Mukherjee (1980) used infrared spectroscopy to probe silica gels with different production methods.…”

Section: Figmentioning

confidence: 99%

Rheology of Silica Sols/Gels Obtained by a Y-Shaped Reactor with a Dilute Method

Kaide

Saeki

2014

J. Chem. Eng. Japan

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Silica sols can be continuously produced by the neutralization of sodium silicate with sulfuric acid using a Y-shaped reactor. The viscosity of the produced silica sols gradually increases, and gels are finally formed through the sol-gel transition. The gelation properties are significantly affected by the preparation conditions. Here we examined the effect of the dilution of silica sols by water in terms of the gelation properties of the silica sols and gels, using both dynamic viscoelasticity measurement and the creep test. Information that is needed to control the gelation properties of silica sols and gels for making silica materials into a product is also presented.

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Sol–Gel Synthesis of Microporous Amorphous Silica from Purely Inorganic Precursors

Cited by 44 publications

References 4 publications

Production of Porous Silica Microparticles by Membrane Emulsification

Production of Porous Silica Microparticles by Membrane Emulsification

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

Rheology of Silica Sols/Gels Obtained by a Y-Shaped Reactor with a Dilute Method

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