Direct Formation of Aerogels by Sol−Gel Polymerizations of Alkoxysilanes in Supercritical Carbon Dioxide

Loy, Douglas A.; Russick, Edward Mark; Yamanaka, Stacey A.; Baugher, Brigitta M.; Shea, Kenneth J.

doi:10.1021/cm970326f

Cited by 110 publications

(109 citation statements)

References 13 publications

(13 reference statements)

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“…As such, SCF solvents offer a distinct advantage for the synthesis and processing of these materials, for the same reasons that SCFs are used to dry silica aerogels. [49,50] Low-density microcellular fluorinated materials were generated by a one-step process which uses scCO 2 and requires no organic solvents. [9,51,52] Highly fluorinated, low molar mass compounds [51,52] and polymers [52] were synthesized which dissolve in scCO 2 and then associate to form gels.…”

Section: Non-reactive Gelation Of Scf Solutions Using Organogelatorsmentioning

confidence: 99%

“…Since the solubility of water in CO 2 is very low, an alternative water-free method was used. [50] Alkoxysilanes such as tetramethoxysilane or 1,4-bis(triethoxysilyl) benzene were polymerized at 35±45 C in scCO 2 (410 bar) in the presence of 13±36 wt.-% formic acid. Gelation occurred within 12 h and the gel was aged for a further 12±18 h. At the end of the reaction, the CO 2 pressure was released to yield silica aerogels in almost 100 % yield to give materials with surface areas in the range 250±600 m 2 g ±1 .…”

Section: Sol±gel Polymerization Of Alkoxysilanes In Scfsmentioning

confidence: 99%

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Porous Materials and Supercritical Fluids

Cooper¹

2003

Advanced Materials

379

247

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Porous materials are used in a wide variety of applications, including catalysis, chemical separation, and tissue engineering. The synthesis and processing of these materials is frequently solvent intensive. In addition to reducing organic solvent emissions, supercritical fluids offer a number of specific physical, chemical, and toxicological advantages as alternative solvents for the production of functional porous materials. The figure shows an electron image of a porous polyacrylate produced by the templating of a concentrated CO2‐in‐water emulsion—a process that would otherwise be highly solvent intensive.

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Section: Non-reactive Gelation Of Scf Solutions Using Organogelatorsmentioning

confidence: 99%

Section: Sol±gel Polymerization Of Alkoxysilanes In Scfsmentioning

confidence: 99%

Porous Materials and Supercritical Fluids

Cooper¹

2003

Advanced Materials

379

247

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“…The method described in this research can be extended to preparing other monolithic columns, e.g., SiO 2 and ZrO 2 , and bimetallics using the direct sol-gel reactions in-scCO 2 techniques [37][38][39].…”

Section: Discussionmentioning

confidence: 99%

Preparing titania aerogel monolithic chromatography columns using supercritical carbon dioxide

Sui

Liu

Lajoie

et al. 2010

J of Separation Science

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The search for a method to fabricate monolithic inorganic columns has attracted significant recent attention due to their unique ability in separation applications of various biomolecules. Silica and polymer based monolithic columns have been prepared, but titania and other metal oxide monoliths have been elusive, primarily due to their fragility. This article describes a new approach for preparing nanostructured titania based columns, which offer better performance over conventional particle packed columns for separating a wide variety of biomolecules including phosphopeptides. TiO(2) monolithic aerogels were synthesized in separation columns using in situ sol-gel reactions in supercritical carbon dioxide (scCO(2)) followed by calcination, and compared to those prepared in heptanes. The characterization results show that scCO(2) is a better solvent for the sol-gel reactions, providing lower shrinkage with the anatase TiO(2) monolith composed of nanofibers with very high surface areas. The monolithic columns show the ability to isolate phosphopeptides with little flow resistance compared to conventional titania particle based microcolumns.

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“…The authors assume that the material synthesis via SCFD also follows the above route of reaction, 22) although no catalytic H 2 O was added in this experiment; unavoidable existence of the adventitious H 2 O in the supplied CO 2 or in TEOS can act as the catalyst and then promote the reaction of hydrolysis. 10) Relationship between thickness of the film and the substrate temperature was plotted in Fig.…”

Section: Deposition Characteristic Against Temperaturementioning

confidence: 99%

Chemical deposition of silica-based thin films under supercritical carbon dioxide atmosphere using tetraethylorthosilicate precursor with oxidizing agents

Uchida

Izaki

Shiokawa

2016

J. Ceram. Soc. Japan

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Supercritical fluid deposition (SCFD) of SiO 2 -based films was proposed using TEOS precursor with oxidizing agents, for the purpose of low-temperature film deposition. The film deposition was performed in a batch-type closed chamber filled with supercritical carbon dioxide (CO 2 ) fluid. The SiO 2 -based films were deposited on aluminum electrodes coated on silicon wafers (Al/Si) at the substrate temperature above 150°C. Oxidizing agents such as O 2 gas and aqueous H 2 O 2 solution promoted the removal of C 2 H 5 OH byproduct and the formation of strong SiO network, whereas it also promoted the homogeneous nucleation of granular precipitation and the H 2 O adsorption in/on the resulting films. The processing temperature of the SCFD was significantly lower than those by thermal CVD and comparable or higher than those by plasma-enhanced CVD, although the resulting films obtained exhibited relatively large dielectric loss which depends on the presence of C 2 H 5 OH and H 2 O byproducts.

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Direct Formation of Aerogels by Sol−Gel Polymerizations of Alkoxysilanes in Supercritical Carbon Dioxide

Cited by 110 publications

References 13 publications

Porous Materials and Supercritical Fluids

Porous Materials and Supercritical Fluids

Preparing titania aerogel monolithic chromatography columns using supercritical carbon dioxide

Chemical deposition of silica-based thin films under supercritical carbon dioxide atmosphere using tetraethylorthosilicate precursor with oxidizing agents

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