Silicon oxide in an iron(III) oxide matrix: the sol–gel synthesis and characterization of Fe–Si mixed oxide nanocomposites that contain iron oxide as the major phase

Clapsaddle, Brady J.; Gash, Alexander E.; Satcher, Joe H.; Simpson, Robert B.

doi:10.1016/j.jnoncrysol.2003.08.068

Cited by 78 publications

(98 citation statements)

References 32 publications

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“…For example, we have shown that the structural properties (e.g., crystallite size and shape, surface area, and porosity) of metal oxide aerogels prepared by this method can be modified by simply changing a single synthetic parameter in the sol±gel reaction, such as the type of epoxide or the anion of the metal salt. [18] In addition, this facile sol±gel method is amenable to the preparation of mixed, metal-oxide systems, [19] providing access to novel, doped-SnO 2 nanomaterials. …”

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confidence: 99%

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

et al. 2005

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confidence: 99%

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

et al. 2005

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“…[15][16][17] This route was recently extended to mixed transition metal oxide aerogels [11,18] and nanocomposites of silica and metal oxide. [19,20] We obtain gels by mixing tetramethoxysilane (TMOS) into methanolic solutions of LaCl 3 · 6H 2 O and then adding propylene oxide; the gels are processed as described in the Experimental section to form three different pore-solid nanoarchitectures. The lanthanum silicate aerogels and ambigels are transparent and monolithic (Fig.…”

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confidence: 99%

Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

Célérier¹,

Laberty-Robert²,

Long³

et al. 2006

Advanced Materials

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Silicate-based oxides are of interest as electrolytes and electrode materials in intermediate-temperature solid-oxide fuel cells (SOFCs). [1][2][3][4][5][6][7] We have developed a sol-gel-based strategy for the production of mesoporous, nanostructured, singlephase La 9.33 Si 6 O 26 apatite in an aerogel-type framework. Silicon alkoxides react with lanthanum(III) aqueous ions in alcohol solutions driven by a proton-scavenging agent, propylene oxide. Varying the means by which pore fluid is removed from the resultant lanthanum silicate gels yields three distinct pore-solid monolithic nanoarchitectures: aerogels, ambigels, and xerogels. The ambigel and aerogel nanoarchitectures exhibit high specific surface areas (from 285 to 408 m 2 g -1), aperiodic through-connected networks of mesopores, and covalently bonded networks of non-agglomerated nanoparticles. Calcination at relatively mild temperatures for this oxide (800°C) converts the amorphous gels to nanocrystalline apatite La 9.33 Si 6 O 26 . Although densified during calcination, the aerogel and ambigel nanoarchitectures retain porosity, high surface area, and limited particle agglomeration. Aerogels and related highly porous architectures are defined by a bonded three-dimensional network of nanoparticles, commingled with interconnected porosity. [8][9][10] The inherent structural characteristics of aerogels are highly beneficial for electrochemical applications, [9] where the high interfacial surface area enhances the kinetics of electrochemical reactions and the continuous mesoporous network facilitates the transport of molecules, ions, and nanoscale objects to the active electrode surface while the solid network of covalently linked nanoparticles promotes charge transport of electrons and ions. It is only recently that aerogel-like materials have been synthesized in electrically conductive, SOFC-relevant compositions and then characterized at operating temperatures. [11,12] An earlier sol-gel route to mixed La-Si oxides modified an acid-catalyzed silica sol-gel method by including lanthanum salts. [13,14] Investigation of a range of hydrolysis rates showed that only very narrow synthesis conditions led to apatite La 9.33 Si 6 O 26 upon calcination (800°C), [1] and impurity phases were common. Subsequent attempts to produce aerogels or ambigels (requiring washing steps with ethanol) led to amorphous oxides after calcination (1000°C), suggesting that this protocol generates a silica network with the lanthanum salt dispersed on its surface.[1]Our approach to synthesize lanthanum silicate nanoarchitectures is based on the initial formation of oligomers of La-O-Si by using epoxide-and alkoxide-driven hydrolysis and condensation reactions. This synthetic protocol is a modification of innovative methods reported by Gash et al. for the preparation of transition metal oxide aerogels. [15][16][17] This route was recently extended to mixed transition metal oxide aerogels [11,18] and nanocomposites of silica and metal oxide. [19,20] We obtain gels by mixing tetramethoxysi...

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“…Examples of interpenetrating aerogel networks have also been reported. For example, the epoxide method has been utilized in the design of interpenetrating iron oxide and silicon dioxide frameworks for use as energetic materials [45][46][47]. Examination of these materials using element-specific TEM clearly illustrates the intimate mixing of the distinct chemical components on the nanometer scale that can be achieved using this approach (Figure 8.8).…”

Section: Mixed Metal Oxide and Composite Aerogelsmentioning

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A Robust Approach to Inorganic Aerogels: The Use of Epoxides in Sol–Gel Synthesis

Baumann¹,

Gash²,

Satcher³

2011

Aerogels Handbook

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Over the last decade, the diversity of metal oxide materials prepared using sol-gel techniques has increased significantly. This transformation can be attributed, in part, to the development of the technique known as epoxide-initiated gelation. The process utilizes organic epoxides as initiators for the sol-gel polymerization of simple inorganic metal salts in aqueous or alcoholic media. In this approach, the epoxide acts as an acid scavenger in the sol-gel reaction, driving the hydrolysis and condensation of hydrated metal species. This process is general and applicable to the synthesis of a wide range of metal oxide aerogels, xerogels, and nanocomposites. In addition, modification of synthetic parameters allows for control over the structure and properties of the sol-gel product. This method is particularly amenable to the synthesis of multi-component or composite sol-gel systems with intimately mixed nanostructures. This chapter describes both the reaction mechanisms associated with epoxide-initiated gelation as well as the variety of materials that have been prepared using this technique. IntroductionAerogels [1, 2] are a special class of open-cell foams that exhibit many interesting properties, such as low mass densities, continuous porosities, and high surface areas. These unique properties are derived from the aerogel microstructure, which typically consists of three-dimensional networks of interconnected nanometer-sized primary particles. Because of their unusual chemical and textural properties, aerogels have been investigated for a wide variety of applications, including catalysis, sorption, insulation, energy storage, and even for cosmic dust collection (Parts VIII-XV). To further expand the utility of these materials, recent efforts have focussed the development of new synthetic processes that can be used to tailor both the composition and structure of aerogels for different applications. Aerogels are typically prepared using sol-gel chemistry, a process that involves the transformation of molecular precursors into highly cross-linked inorganic or organic gels that can then be dried using special techniques to preserve the tenuous solid network. For organic and carbon

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Silicon oxide in an iron(III) oxide matrix: the sol–gel synthesis and characterization of Fe–Si mixed oxide nanocomposites that contain iron oxide as the major phase

Cited by 78 publications

References 32 publications

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

A Robust Approach to Inorganic Aerogels: The Use of Epoxides in Sol–Gel Synthesis

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Silicon oxide in an iron(III) oxide matrix: the sol–gel synthesis and characterization of Fe–Si mixed oxide nanocomposites that contain iron oxide as the major phase

Cited by 78 publications

References 32 publications

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO2 Aerogel

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO2 Aerogel

Synthesis of La9.33Si6O26 Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry

A Robust Approach to Inorganic Aerogels: The Use of Epoxides in Sol–Gel Synthesis

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Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

Facile Synthesis of a Crystalline, High‐Surface‐Area SnO₂ Aerogel

Synthesis of La_9.33Si₆O₂₆ Pore–Solid Nanoarchitectures via Epoxide‐Driven Sol–Gel Chemistry